LDTP - 77-4
Technical Report
Tire-Dynamometer Roll Effects
by
Richard N. Burgeson
March 1978
Notice
Technical reports are intended to present a technical analysis of
an issue and recommendations resulting from the assumptions and constraints
of that analysis. Agency policy constraints or data received subsequent
to the date of release of this report may alter the recommendations
reached. Readers are cautioned to seek the latest analysis from EPA
before using the information contained herein.
Standards Development and Support Branch
Emission Control Technology Division
Office of Mobile Source Air Pollution Control
Office of Air and Waste Management
U. S. Environmental Protection Agency
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CONTENTS
I. Introduction
II. Summary and Conclusions 1
III. Technical Discussion 4
A. Program Objectives 4
B. Program Design 4
C. Equipment 5
D. Dynamometers 5
E. Tires 7
F. Data Collection 7
G. Analysis 8
H. Test Procedure 10
IV. Results 10
A. Effects of Dynamometer Horsepower 10
Setting
B. Effects of Tire Size 11
C. Effects of Tire Types 11
by Dynamometer
D. Effects of Tire Manufacturer
E. Correction Factor Development 17
V. Conclusions 20
VI. Recommendations 21
VII. References 22
VIII. Appendices
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I. Introduction
Currently, the Federal Government determines light-duty vehicle
fuel economy and emissions on the twin small-roll dynamometer. The
vehicle is driven according to a specific speed-time cycle while its
emissions are monitored and then its fuel consumption derived. It has
been speculated that a vehicle being driven on a dynamometer may not be
representatively tested. The geometry of the dynamometer-vehicle system
is one which cannot be duplicated under actual driving conditions
because only the vehicle rear tires are placed on the dynamometer and
the surface upon which they are placed is curved. In the case of the
twin small-roll dynamometer, the tires are placed between two cylinders
approximately 17" apart. Due to this configuration, the tire deforms in
two areas, one area at each cylinder-tire contact point, instead of only
one area as on the road. The abnormal deformation on the dynamometer
tends to require the tire to absorb a greater portion of the power
transmitted to it than would the same tire on a flat road surface. It
is generally assumed that the power absorbed by the tire (at 45 psi) on
the dynamometer is twice that of the tire (at 26 psi) on the road. If
such an assumption is true, the use of the twin small-roll dynamometer
for emissions and fuel economy testing is technically justified if all
tires behave in the same manner and in-use tire pressures remain at 26
psi. The increase in tire power absorption by a factor of two on the
dynamometer accounts for the front two tires on the road.
Recently, questions have been raised as to the validity of the
assumption that two tires on the dynamometer equals four tires on the
road with regard to all tire construction types (radial, bias belted,
and bias ply). Technical literature dealing with tire rolling forces on
a flat surface, reports that, in general, radial tires exhibit lower
rolling resistance (it takes less force to start and perpetuate tire
roll) than the other two tire construction types. However,, it has been
suggested that when radial tires are operated on the twin small-roll
dynamometer they exhibit higher rolling resistance than the other two
construction types under the same conditions.
To resolve the above question, all available technical literature
was reviewed. Unfortunately, information concerning tire^rqlling
resistance on the twin small-roll dynamometer was scarce. ' This lack
of information prompted an in-house investigation into the effects of
the twin small-roll dynamometer on tires.
II. Summary and Conclusions
In order to resolve the question concerning the effects of the twin
small-roll dynamometer on tire power absorption, 29 pairs of tires
ranging in size from a BR78xl3 to an LR78xl5 and consisting of three
common construction types (radial-belted, bias belted, and bias ply)
were tested. The construction-type distribution of the sample consisted
of 72% radial (belted), 14% bias belted and 14% bias ply tires. The
method chosen to evaluate the effects on tire power absorption of the
twin small-roll dynamometer was to monitor the power transmitted from a
vehicle traveling at a velocity of 50 mph and the power received by the
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dynamometer. Any difference was considered to be the amount of power
absorbed by the tire. The identical process was then repeated on a
single large-roll (48" diameter) dynamometer. The single large-roll
dynamometer test results were then corrected to a flat surface so that a
comparison to the road could be accomplished. All the tires tested had
an initial (cold) pressure of 45 PSIG which was unregulated during
testing (capped air method). Each test period consisted of an acceler-
ation, by the vehicle, to a velocity of 50 mph and this velocity sus-
tained for a minimum period of 20 minutes. The initial 15 minutes of
each test period were considered warm-up to insure tire, vehicle and
dynamometer temperature stability throughout each test. Figure 1 depicts
typical tire rolling resistance characteristics as a function of time at
a velocity of 50 mph on a flat test surface. Note that after approxi-
mately 900 seconds the tire rolling resistance is nearly constant, so
that the assumption of stability was justified. At the end of the test
period the vehicle was then decelerated to 0 mph and a different pair of
tires installed. The vertical load on each test tire was held as con-
stant as the vehicle rear suspension system would allow and was consi-
dered to be one-half the rear weight of the vehicle.
From the data collected, the effects of the twin small-roll dynamometer
were quite evident. Initial data analysis indicated that at 45 PSIG,
radial, bias belted and bias ply tires of the sample absorbed 2.65, 2.04
and 1.82 times, respectively, more power on the small twin-roll dyna-
mometer than would the same tires at the same pressure (45 psi) on the
road.
The increased power absorbed by the tire on the twin small-roll
dynamometer is to take into account the front two tires of the vehicle
which are not on the dynamometer, but would be operating on the road.
This is the same as saying, "two tires on the small twin-roll dynamo-
meter act like four tires on the road." However, if this explanation is
accepted, then the power absorbed by the tire on the small twin-roll
dynamometer should be twice that required by the road. As can be seen
from the results above, this is not quite the case for all tire types at
45 psi inflation pressure. However a pressure of 45 PSIG is not a
normal operating tire pressure on the road. Therefore, a correction
factor to estimate the tire power absorption on the road at 26 PSIG, a
reasonable operating tire pressure for the road, was applied and the
analysis repeated. The results indicated that radial, bias belted and
bias ply tires in this sample absorb 1.68, 1.30 and 1.15 times, respec-
tively, more power on the small twin-roll dynamometer (with the standard
test inflation pressure) than the same tires on the road with a tire
inflation pressure of 26 PSIG. This implies that the tires are not
totally accounted for by the interaction of the tires and the dynamo-
meter rolls when a vehicle is tested for emissions and fuel economy.
According to the Federal Test Procedure the aerodynamic road load
effects are estimated based on the test vehicle's aerodynamic charac-
teristics. For radial tires, these procedures assume that the two tires
on the twin small-roll dynamometer absorb the same power required by a
vehicle on the road (i.e., two tires on the dynamometer equal four on
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PQ
0)
a
c
n)
4J
co
H
CO
OJ
Pi
M
c
35.0D
i
30.00'
^
<
25.00'
20.00
15.00
30.80
5.000
w-tw
200.0 400.0 6Q0.0 800.6 1000.0 1200.0 1400.0 1608.0
TIME ELAPSED (SEC)
Tire Rolling Resistance Characteristics versus Time
Figure 1
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the road). However, this experiment suggests that two radial tires on
the dynamometer are equivalent to approximately 3.4 tires on the road.
Perhaps different dynamometer road load power absorber settings (e.g.,
correction factors) or lower tire pressures should be used for federal
testing to account for differences among tire types. A different dyna-
mometer which would better simulate the tire-road interaction may also
be indicated.
In addition to the above results, an investigation into the effects
of dynamometer horsepower setting, tire size, tire type and manufacturer
was conducted. In general, this experiment could not detect a signifi-
cant effect on tire rolling resistance due to dynamometer horsepower
setting or tire size. However, it was found that when tire rolling
resistance values were ranked by tire type in an increasing order, the
rankings for each test dynamometer were different. The single large-
roll dynamometer ranked the tire types as one would expect of the road;
radials, bias belted, bias. The twin small-roll dynamometer ranked the
same tires; bias belted, radials, bias. It was found that significant
differences between tire types on the twin small-roll dynamometer could
not be detected, whereas, on the single large-roll each tire type was
significantly different from each of the other tire types. As for tire
manufacturer, significant differences could be detected for radial and
bias belted tires on the twin small-roll dynamometer, however, on the
single large-roll, significant differences could only be detected for
bias belted tires.
III. Technical Discussion
A. Program Objectives
The basic objectives of this test program were as follows:
1. To determine the relative power consumption rankings of bias,
bias belted and radial ply tires on the twin small-roll (Clayton) and
single large-roll (Electric) dynamometers,
2. If possible, determine the effects of dynamometer horsepower
setting, tire size and tire manufacturer on tire power absorption for
each of the dynamometers above, and
3. To possibly develop a correction factor which will allow a
better simulation of tire power consumption on the road when a vehicle
is tested on a Clayton dynamometer.
B. Program Design
Tire power absorption data were collected on both single large-roll
and twin small-roll dynamometers. Twenty-nine pairs of tires were
tested on each dynamometer at an average of two (2) dynamometer road
load horsepower settings per pair of tires. The dynamometer horsepower
settings were based on nominal tire size and normal vehicle weight. All
the tires tested had an initial inflation pressure of 45 psig which was
permitted to increase during testing (capped air method).
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A mean tire power absorption was computed by tire type for each
dynamometer and statistical .tests for significant differences between
dynamometers were then performed. The data generated were analyzed with
respect to tire type, tire size, dynamometer horsepower setting and
manufacturer.
C. Equipment
1. Test Vehicles
For the program, two vehicles were utilized, a 1971 Ford station-
wagon and a 1972 Vega stationwagon. The 14 and 15 inch tires were
tested on the Ford and the 13 inch tires were tested on the Vega. Each
vehicle was equipped with an optical encoder from a "T" in the speedo-
meter cable at the transmission to measure vehicle speed and a drive-
shaft torque sensor to measure the torque output of the engine-trans-
mission. With those items, the power to the tire was monitored.
Although a driveshaft torque sensor measures the torque supplied by
the engine- transmission, the actual torque at the tire is somewhat less
due to rear axle and bearing losses. The torque supplied to the tire
may be expressed by the following equation:
"T T1 _ rP
tire eng. diff. (1)
where
T = torque from the engine/transmission (measured by the
driveshaft torque sensor)
= torque required to revolve the rear axle and associated
bearings and gearing which make up the differential.
Note: Brake drag was minimized by backing off the
brake shoes and deactivating the self-adjusters.
In order to determine the torque due to the differential losses,
T , the rear wheels of each vehicle were raised off the ground and
the driveshaft torque at velocities from 10-60 mph was monitored.
Vehicle velocity was increased and decreased in 10 mph increments.
Thirty seconds of data were collected at each velocity. Prior to data
collection, the differential underwent a 30 minute warm-up period to
stablize the differential lubricant temperature and minimize any bearing
losses. A linear regression analysis was then performed to obtain the
torque T, f as a function of driveshaft speed for both vehicles to be
utilized during tire testing.
D. Dynamometers
Two dynamometers were utilized for the experiment, a standard twin
small-roll Clayton and a single large-roll (48" diameter) LABECO. Each
dynamometer roll was equipped with magnetic proximity detectors to
record roll speed. In addition, each dynamometer load cell torque
sensor signal was interfaced and recorded throughout the experiment.
Although the dynamometer load cell torque is a good indication of the
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torque being transmitted by the tire, the sensor does not detect the
torque the tire must apply to the roll in order to overcome the internal
friction of the dynamometer. Therefore, to determine the torque at the
roll surface, the torque due to bearing losses must be added to the load
cell torque as indicated by equation 2:
TR = TLC + TBL (2)
where
T = Torque at the tire/roll interface
K.
T = Total torque from the load cell
JjL*
T,,T = Torque due to bearing and friction losses in the dynamometer.
ijL
To determine the torque due to bearing friction losses, the dynamo-
meter was coasted down from 55 mph to 45 mph and the roll speed and T
monitored. T may be computed using the following equation:
K
T = I cc
R D
where
I = the inertia of the system
<* = angular acceleration of the roll
<* may be approximated by:
a/ Aw
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550 x horsepower setting
T = W
where
T = electric dyno torque at 50 mph
Tt , T , linear velocity
W = the angular velocity = L- 7; r
radius of rotation (Clayton)
The computed torque was then "dialed in" while the test vehicle was
operating at 50 mph. This was accomplished utilizing the "windage"
potentiometer of the dynamometer controller. The "windage" electrical
signal increases or decreases the absorption torque as a function of the
velocity squared, as does the twin small-roll water brake power absorber,
therefore, approximately duplicating the twin small-roll dynamometer
horsepower curve.
E. Tires
A total of 29 pairs of tires were tested for their relative power
absorption on two dynamometer types. Twenty-one of the 29 pairs of
tires sampled were General Motors (GM) specification tires procured from
GM. The balance were procured from local tire dealerships and were
considered to be of original'equipment manufacturer replacement quality.
Of the tires tested, 72% were belted radials, 14% were bias belted, and
14% were bias ply tires. The range of sizes tested were from a B 78x13
to an LR 78x15. A complete list of the tires tested is contained in
Appendix C.
Available literature indicates that all new tires undergo a period
of cord settling and stretching once placed into service. Any measure-
ments of tire power absorption during this period would be inaccurate
and not considered typical. Therefore, a minimum of 300 miles were
accumulated on each pair of tires. 250 miles of the 300 miles were
accumulated on a large single-roll dynamometer by mounting the tires on
a vehicle and then maintaining a velocity of 50 mph. The remaining 50
miles were accumulated on the road at varying speeds. The initial cold
tire pressure during mileage accumulation was 26 PSIG and 28 PSIG for
13" and 14"-15" tires, respectively.
F. Data Collection
In order to collect as much data in as short a period of time as
possible, all parameters were recorded at a second-by-second rate on
magnetic tape. A 7-track Kennedy tape recorder was utilized to record
vehicle and dynamometer-roll speeds, vehicle and dynamometer torques,
real time, test identification code, tire manufacturer code, and tire
size code. Data were collected for a minimum period of 20 minutes per
dynamometer type and tire pair, in order to allow the tires to reach
approximate temperature and pressure equilibrium. However, only data
collected after the first 15 minutes were utilized.
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G. Analysis
The power absorbed by the tire was computed each second for all
data points after the first 900 seconds according to the following
equations:
P=P -P -P -P (4)
AT engine abs. diff. abs. dyno bearing lossed dyno.
= T W-T W-TW-TW
eng E diff E LC D BL D
= (T - T..-.)W_. - (T + T )W (5)
eng diff E LC BL D
where
P is the power absorbed by the tire,
T and T, are as defined in (1),
T^8and T are as defined in (2),
W and W are the angular velocities of the vehicle drive-
snaft ami dynamometer roll, respectively.
From each P the rolling force was then derived as follows:
PAT = TTWT (6)
where T is the torque at the tire/roll interface and W is the angular
velocity of the tire. However, T can be defined as the product of a
force and a lever arm as follows:
TT = FR x r (7)
where F is the rolling force of the tire and r is the tire radius.
Substituting equation (7) into (6) yields:
PAT = (FR X r) WT (8)
Since the angular velocity W can be represented as a ratio of the
linear velocity, V , and the radius of the tire, r, a substitution for
W in equation (8) produces:
(F x r)V
P = - - = F V (9)
AT r R T ^
the linear velocity V is in actuality the ground or test surface
velocity. However, with all vehicle tests on dynamometers, a certain
amount of tire slip occurs. For this reason, the vehicle linear velocity,
the one parameter common to both dynamometers, rather than the dyna-
mometer-roll linear velocity was utilized for this analysis. Therefore,
F can be expressed as,
PAT
F =
Vrp
where V- is the vehicle speed. (10)
i
Mean values for the vehicle speed, V , power absorbed PAT> and the
rolling force F , were then computed for each test and considered a data
point for that particular set of tires. Due to technician error and
accelerator-control drift, it was found that the mean vehicle speeds.
varied from test to test by a maximum of 5 mph. These speed variations
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make any direct data comparisons difficult. In order to resolve this
problem and enable valid statistical comparisons to be made, a specific
velocity of 50 mph was chosen and a new P. computed. This was accomp-
lished by first determining F from equation 10 utilizing the test P.
and the test velocity. This value of FR and the chosen V were then
substituted into equation 9 and the new value for P. computed. It
should be noted from equation 10 that F_ is far less sensitive to speed
variations than is PAT- Indications from the technical literature are
that an approximate error of only 0. 3% per mph is introduced by such an
estimate. ' '
Of all the parameters affecting tire power absorption, the vertical
load on the tire has yet to be discussed. In general, tire power absorp
tion is directly proportional to the load upon it. As the vertical
load increases, the tire power absorption also increases. Therefore,
all the above computations are a function of the vertical load under
which a particular set of tires was tested. The vertical load used for
this experiment was arrived at by weighing the rear portion of each test
vehicle with a full tank of fuel and a driver. Fuel was added to each
test vehicle at the completion of every second test in order to maintain
as constant a vertical load as possible. However, the vertical load of
the two test vehicles differed, therefore, making direct tire rolling
force, F , data comparisons difficult. By calculating the ratio of F
to the test vertical load, F , all tire test results could then be
directly compared. This is expressed in the equation below:
However, statements concerning the power absorbed at 50 mph, PAT» for
all the data still could not be made. , Since the tire rolling rorce, F ,
is nearly linear with vertical load, ' ' estimates of the power absorbed
at 50 mph can be obtained using a form of equation 11. Using the rolling
resistance values, F , previously obtained, a standard vertical load
was chosen and the power absorbed at 50 mph was predicted. The equations
presented below outline this process:
FRN = FRR X FZN
PATN = FRN X 5°
where F is as defined in equation 11 and
KR
F = normalized F
KIN K
F = 2.985 x 103 Ibs.
PATN= normalized PAT
The standard vertical load was chosen to be the rear weight of the
Ford stationwagon used to test 14" and 15" tires. This selection was
based on the number of tests conducted at that vertical load, so that
only those data generated for 13" tires required normalization. Data
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from all the tires tested were then grouped by test dynamometer (Clay-
ton, Electric) and statistical tests for significant differences between
mean test results were then performed. In addition, analyses of vari-
ance were conducted to determine the effects of tire size, dynamometer
horsepower setting and tire manufacturer on P.., for each test dynamometer.
AJ. JN
H. Test Procedure
Prior to the commencement of testing on a given day, the test
dynamometer and vehicle were warmed-up for 30 minutes at a steady state
velocity of 50 mph. Upon completion of this warm-up period, the dynamo-
meter road load horsepower was set, if required. The warm-up tires were
then removed from the vehicle and a pair of test tires were installed.
An initial cold tire pressure of 45 PSIG was set upon installation of
the test tires. The test vehicle was then accelerated to 50 mph and
this velocity sustained for a minimum of 20 minutes. Data collection
began upon vehicle acceleration. Upon completion of the test period,
the vehicle was decelerated to 0 mph and a new pair of test tires
installed. The time to change tires averages approximately 5 minutes.
The above process was repeated for each pair of test tires for approxi-
mately 4 different road load horsepower settings per test dynamometer.
The purpose of the rapid tire changing was to minimize dynamometer
and vehicle lubricant cooling which would increase the bearing and
frictional losses. Once tested, a given pair of tires were not retested
unless a minimum of 4 hours had elapsed. This allowed the tires to
return to ambient temperature and reduced tire damage from excessive
heat. Fuel was added to the vehicle after every second test to minimize
tire verticle load fluctuations. Each set of tires was tested at an
average of two (2) dynamometer horsepower settings. A total of 120
tests (61 Electric and 59 Clayton) were conducted.
IV. Results
The following analyses for the effects of dynamometer horsepower
setting, tire size, tire manufacturer and tire type on tire power
absorption were conducted on the data for tires inflated to 45 psig on
each dynamometer.
A. Effects of Dynamometer Horsepower Setting
In order to isolate the effects of dynamometer horsepower setting,
the sample was separated by nominal tire size and tire type for each
dynamometer. A correlation analysis was performed on the test data.
The results of this analysis indicate that, in general, no significant
effects on P.TM could be discerned due to dynamometer horsepower setting
on either dynamometer. There were, however, two cases (one on each
dynamometer) where a significant correlation resulted. These cases were
for 14" radial tires on the twin small-roll dynamometer and 13" radial
tires on the single large-roll dynamometer. In both cases the power
absorbed at 50 mph, PATN> decreased with increasing dynamometer horse-
power setting. These results are consistent with those reported in the
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literature on a flat test surface within the range of forces applied in
this experiment. Plots of PATM> the power absorbed at 50 mph, as a
function of dynamometer horsepower setting by tire size and type are
presented in Appendix F for both dynamometers. The fact that, in general,
no effect could be discerned could be due to tire slip on the rolls and
test variability. By defining tire slip for the small twin-roll dyna-
mometer as the difference between rear roll speed and front roll speed
and plotting tire slip as a function of dynamometer horsepower setting,
it can be seen that tire slip increases with increasing horsepower
setting. Figure 2 depicts these variables for 13" radial tires. The
effect of horsepower setting may be masked by this loss of tractive
effort in combination with test variability. It is assumed that tire
slip occurs on the road, but to what extent is not yet known.
Since the effects identified as significant were small (1 case in 6)
it was deemed that the overall conclusions would not be affected. The
data were therefore combined for further analysis.
B. Effects of Tire Size
The sample was segregated into three groups based on nominal tire
size (13", 14", and 15") to determine the effects on P and F . It
was found that on either dynamometer, 13" tires were significantly
different from 14" and 15" tires. These initial findings could have
been caused by the interaction effect of tire type (i.e., 13" tires
exhibited lower rolling resistance because there were more radial 13"
tires than radial 14" and 15" tires). Therefore, to isolate this inter-
active effect, the ANOVA was repeated, however, this time controlling
for tire type. The results of the second ANOVA indicated that an effect
on P,TN could not be detected on either dynamometer. This does not mean
to say that tire size has no effect on rolling resistance, but that this
experiment could not detect any. To resolve any effects due to tire
size, variables such as manufacturer and tire type would have to be
controlled when performing the ANOVA. Unfortunately, attempts to do so
created holes in the analysis matrix which made any results questionable.
C. Effects of Tire Type
Since significant effects on PATM and F due to dynamometer
horsepower setting and tire size coula not be detected, the combined
data were segregated by tire type. An analysis of variance was then
performed on these data for each test dynamometer. The results indi-
cated that for the case of the twin small-roll dynamometer, differences
between tire types could not be discerned. For the single large-roll
dynamometer, each tire type was significantly different from the other
tire types. A summary of the statistical comparisons are presented in
Tables 1 and 2 by dynamometer. These results would indicate that the
geometry of the twin small-roll dynamometer forces the tires to absorb a
similar amount of power regardless of construction type.
Figures 3 and 4 are plots of the normalized power absorbed at 50
MPH, PATN» as a function of tire type for the twin small-roll and
single large-roll dynamometers, respectively. The overall shift of the
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<5TRAT=VI '*Vi: I INTfefeVAU=C -1 > : (2- 1
N= JQ OUT 0^ 19 S.OFLJRSP VS. 4. HP
DELRSP (MPH)
1. 160 *
1.030 +
0.900
0.772
§
I O
0.643
» o 03
o* ^ c
H- o *
0.515
H rt
(0(1)
0.386
. 0.257 *
0.129
n>
o
3
no
0.
3.000O 4.000O 6.QOOO)
3.0000 5.0000 7.0000
10.000 HP Setting
9.0000 11.000
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Table 1
Mean Level Comparisons Between Tire Construction
Types On The Twin Small-Roll (Clayton) Dynamometer
Mean Mean . Degrees Significance
Power Absorbed at Rolling Resistance F-Stat of at 95%
50 mph, P... (watts) F (Ib/k-lb) Freedom Confidence
A. J.N JxEx
Radial/
Bias 5721.961/5212.867 19.282/17.567 2.515 39,10
Belted
Radial/ 5721.961/5829.297 19.282/19.644 0.086 7,39
Bias
Bias
Belted/ 5212.867/5829.297 17.567/19.644 1.979 7,10
Bias
No
No
No
Table 2
Mean Level Comparisons Between Tire Construction
Types On The Single Large-Roll (Electric) Dynamometer
Mean Mean Degrees
Power Absorbed at Rolling Resistance F-Stat of
50 mph, PATM (watts) F (Ib/k-lb) Freedom
A UN K.K.
Radial/
Bias 2689.754/3150.111 9.064/10.615 4.078 41,10
Belted
Radial/ 2689.754/3994.747 9.064/13.462 25.262 7,41
Bias
Significance
at 95%
Confidence
Yes
Yes
Bias
Belted/ 3150.111/3994.747 10.615/13.462
Bias
7.294
7,10
Yes
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SCATTER PLOT <1> DYNO TYPEtCLAYTON
PATN(WATTS)
9000.0 *
8000.0
7000.0
z
o
i
0)
.0
n
o
m
6000.0
5000.0
3
3
3
5
5
o
S i
o
2
H
In
O
n
M
o
i
o
OJ
N
4000.0
3000.0
2000.0
1000.0
o
H
i
O
n
3
n
0.
1
HADIAL
BELTED
5
BIAS
TIRE TYPE CODE
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SCATTER PLOT OYMO TYPE:ELECTRIC
4
PATN(WATTS)
9000.0 +
8000.0
7000.0
o
» 6000.0 +
o
to
en
S
s
f en
« S
t-i to
"> 5000.0 +
4-1
CO
a
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H /^
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data, in Figure 4, to lower power absorption is due to the more natural
footprint of the tire on the single large-roll dynamometer. The large
amounts of overlap in PATN of the different tire types may be due to the
differences in load carrying capacity (F, G, H, etc.) within each tire
manufacturer and between each manufacturer. The corresponding plots to
Figures 3 and 4 for F are presented in Appendix A. In addition,
scatter plots of PATN and F as a function of dynamometer type for each
tire type are also presented in Appendix A.
The large scatter of the data for the bias and radial ply tires on
the twin small-roll dynamometer lead to an investigation of the maximum
and minimum PATN values. The tires with maximum and minimum PATN values
in these categories were identified for each dynamometer. It was found,
in the bias ply category, that the tire with the maximum PATM value on
the twin small-roll dynamometer also had the maximum value on the single
large-roll dynamometer. The same was indicated for the minimum values.
In the radial ply category, the tire with the minimum PATN value on the
twin small-roll dynamometer also had the minimum value on the single
large-roll dynamometer. However, the tire with the maximum PATN value
on the twin small-roll dynamometer in this category did not have the
maximum value on the single large-roll, but its value was above average.
Conversely, the tire with the maximum PATM value on the single large-
roll dynamometer attained an above average value of PATM on the twin
small-roll dynamometer.
A comparison of the replicate tests conducted on the tires in
question indicates that these tires displayed a large test-test vari-
ability. This variability may be due to a change in some parameter or
parameters, such as vehicle speed or vertical load, which went unnoticed
and unrecorded. Since rejection of these data points affects the mean
values only slightly and does not affect the overall results obtained
above, these data points were not removed.
The increasing variability from radial to bias belted and from bias
belted to bias ply tires could be the presence (or lack of) a belt
beneath the tread. The material and design of the belt may also have an
effect on PATN« Test to test variability could also be another expla-
nation. Figure 5 depicts PATN as a function of manufacturer for 15"
radial tires tested on the small twin-roll dynamometer. Beside each
data point, the corresponding tire identification number appears. As
can be seen, in most cases the test to test repeatability for a given
manufacturer's tire is fairly good (approximately 8%). However, some
tires are more repeatable than others.
Upon completion of the data analysis as described above, rankings
of the three tire types for each dynamometer were completed. Tables 3
and 4 present the rankings of the computed mean values for the power
absorbed at 50 mph, PATN> and the tire rolling resistance, F . The
tire type with the lowest power absorption was ranked "1" and that with
the highest ranked "3". As can bee seen from the Tables, the rankings
of the respective tire types differ from test dynamometer to test dyna-
mometer. Although the single large-roll dynamometer is not the road,
the rankings for the respective tire types are in agreement with previ-
ously published data on a flat test surface.
-------
TTRESIZE:SlSOTI«Ei YPE :PAOTALOOYNOTYPF:CLAY
N= 3? OUT OF 22 4.PATN >>S. S.MFO
PATN (Watts)
9000.0 *
8000.0
7000.0
»-16B
?-12B/420
»-16B
hOOO.O
n
3
,c
O.
B
o
5000.0
O
to
S
a)
3
o
PL.
o
z.
^000.0
3000.0
aooo.o
1000.0
0.
»-16A
o-12B
«-080
»-080
»-200
»-070
»-220
»-200
'-400
-240
<>-400
o-290
o-180
o-230
o-230
Goodyear
Goodrich
Uniroyal
Firestone
General
-------
-14-
Table 3
Relative Ranking On Tire Construction Types
On The Twin Small-Roll Dynamometer
Mean Mean
Tire Type Ranking Power Absorbed Rolling Resistance
at 50 mph (Ib/k-lb load)
Radial
Bias Belted
Bias
2
1
3
(Watts) (PATN)
5721.961
5212.867
5829.297
(V
19.282
17.567
19.644
Ranking Scheme
1 = lowest power absorption at 50 mph.
3 = highest power absorption at 50 mph.
Table 4
Relative Ranking Of Tire Construction
Types On the Single Large-Roll Dynamometer
Mean Mean
Tire Type Ranking Power Absorbed Rolling Resistance
at 50 mph (Ib/k-lb load)
(Watts)
(p ) (F )
* ATN' * RR'
Radial 1 2689.754 9.064
Bias Belted 2 3150.111 10.615
Bias 3 3994.747 13.462
-------
-15-
D. Effects of Tire Manufacturer
The tires for this test program were made by five popular American
Manufacturers; Good year, B.F. Goodrich, Uniroyal, Firestone, and
General. By analyzing the test data with respect to tire type and
manufacturer it is possible to determine the relative rankings of the
manufacturers' products based on the power absorbed at 50 mph, PATN>
mean values for each tire type. Tables 5 and 6 show these results as
the percent deviation from the mean PATN for the twin small-roll dyna-
mometer and the large single-roll dynamometer respectively. As an
example, note that for radial tire_s on the single large-roll dynamometer
(Table 5), Goodyear is 10.61% below the mean P. (indicated by the
"minus" sign) and B.F. Goodrich is 9.76% above. This same type of
ranking is also displayed on the twin small-roll dynamometer. Scatter
plots of P.TM versus manufacturer for each dynamometer tire type are
presented in Appendix B.
By performing an analysis of variance (ANOVA) on the power absorbed
at 50 mph, P,TN> the tire rolling resistance, and FRR> the effect due to
tire manufacturer with respect to tire type was determined. The results
of the ANOVA are summarized below:
Large Single-Roll Dynamometer
Radials
Bias Belted
Bias
Significant Difference
due to Manufacturer
NO
YES
NO
Small Twin-Roll Dynamometer
Radials
Bias Belted
Bias
Significant Difference
due to Manufacturer
YES
YES
NO
A more detailed ANOVA was then conducted to determine which manufac-
turers were causing the effect. For radial tires on the small twin-roll
dynamometer it was found that Goodyear, Uniroyal and Firestone displayed
significantly less rolling resistance (and absorbed power) than B.F.
Goodrich. No conclusions were drawn concerning General tires due to
insufficient data. For bias belted tires, Goodyear was signficantly
different from Uniroyal and Firestone on either dynamometer and in the
case of the twin small-roll, Uniroyal and Firestone tires were signifi-
cantly different from each other (B.F. Goodrich and General bias belted
tires were not tested).
The relative insensitivity of the large single-roll dynamometer is
most likely due to the abnormal tire pressure (45 PSIG) at which the
tires were tested. If a reasonable tire pressure of 26 PSI were uti-
lized, more normal cord and sidewall flexing would take place so that
the method of manufacture would become more critical in regard to the
tires ability to transmit power. Attempts to further segregate the
sample by controlling the analysis by manufacturer as well as tire size
and construction type, left holes in the analysis matrix rendering any
results questionable.
-------
-16-
Table 5
Percent From The Power Absorbed at 50 MPH, PATN> Grand Mean by
Manufacturer and Tire Type (Single Large-Roll Dynamometer
- Uncorrected to Road or Increase Tire Pressure).
Percent Deviation from Grand Mean
Tire Type Grand Mean Goodyear Goodrich Uniroyal Firestone General
Radial 2689.754 -10.61 9.76 1.64 6.25 -8.77
Bias Belted 3150.111 -14.48 NONE 15.69 8.45 NONE
Bias 3994.747 NONE -0.38 1.15 NONE NONE
NONE = None tested.
Table 6
Percent From The Power Absorbed at 50 MPH, P»TN> Grand Mean by
Manufacturer and Tire Type (Twin Small-Roll Dynamometer)
Tire Type
Radial
Bias Belted
Bias
Percent Deviation from Grand Mean
Grand Mean Goodyear Goodrich Uniroyal Firestone General
5721.961 -8.10 15.38 0.02 -0.74 -2.00
5212.867 -12.98 NONE 3.49 18.14 NONE
5829.297 NONE 1.64 -2.74 NONE NONE
NONE = None tested.
_ , ,. Manufacturer PArT,,T Mean - P.mT Grand Mean
Percent from P Grand Mean = ATN ATN
P Grand Mean
A J_ IN
-------
-17-
E. Twin Small- Roll Dynamometer Road Correction Factor Development
One of the objectives of this experiment is to develop a twin
small-roll dynamometer to road correction factor. It should be noted
that the accuracy of any relationship developed is questionable due to
the data scatter. The following computations attempt to take into
account this variability.
The basic relationship between the test dynamometers can be ob-
tained by comparing the mean value for the power absorbed at 50 mph,
P. , for each tire type across the two test dynamometers. From Figures
3 and 4 it can be seen that an obvious difference between the test
dynamometers exists. In order to determine if this difference is signi-
ficant, an analysis of variance was perfromed on PATN by tire type. It
was found that for each tire type the difference between test dynamometers
is significant. The magnitude of this difference was then determined by
computing the ratio of mean PATN values on the twin small-roll dynamometer
to the mean PATN values on the single large-roll dynamometer by tire type.
The equation below summarizes the computation performed for each tire
type. Table 7 presents the ratios obtained and their significance.
mean P,m.T on twin small-roll
ATN
CE mean PATM on single large-roll
A .LIN
Table 7
Ratio of Mean Levels and Relative Significance
Radials
Bias Belted
Bias
Mean Level Ratio
R *
CE
2.13
1.65
1.46
Significance
at 95% Confidence
Yes
Yes
Yes
Student's T
Statistic
17.636
7.42
3.014
Degrees
of
Freedom
73.6
20
14
* These results are for tires inflated to 45 PSIG on both dynamometers.
It should be noted that a correction factor is required when comparing
force or power measurements obtained on the single large-roll dynamometer
to that of the road. This is due to higher rolling losses produced by
the roll curvature. The curved surface causes greater maximum deflection
of the tire than would have occurred on the road with the same vertical
load. The required correction factor is a function of the loaded tire
radius and the roll radius. ' Equation 15 shows this relationship:
,-1/2
(15)
DR
where
DR
= correction factor from dynamometer roll to the road
-------
-18-
r = loaded tire radius
R = roll radius
Force or power measurements taken on the dynamometer would be multiplied
by equation 15, therefore decreasing those values of F and PATN
obtained on the single large- roll dynamometer.
The loaded tire radii utilized for this correction were obtained by
measuring each tire from the ground to the top surface while mounted on
the appropriate test vehicle and dividing this measurement by 2. A
complete listing of the tire loaded and unloaded radii by tire identi-
fication number is contained in Appendix E.
By substituting the appropriate values into Equation 14, a correction
factor for each tire tested was generated. The mean correction factor
for each tire size is present below.
Nominal Tire Size C
13 inch .819
14 inch .811
15 inch .799
Using the correction factors computed for each tire, the single
large-roll dynamometer power absorption and rolling resistance, F ,
data were corrected to a flat surface and new mean power absorption
values were calculated for each tire type. The corrected mean PATvr F
values for each tire type are shown in Table 8.
Table 8
Curvature Corrected Single Large-Roll Dynamometer Power and Force
Measurements To The Road At An Inflation Pressure Of 45 PSIG
Tire Type
Radials
Bias Belted
Bias
Ranking
1
2
3
Mean
Mean
Power Absorbed Rolling Resistance
at 50 mph (Ib/k-lb load)
(Watts) (PATN)
2165.252
2548.489
3207.782
7.297
8.588
10.810
Curvature
Corrected
RCE
2.65
2.04
1.82
Although the single large-roll dynamometer results have been corrected
to a flat road-type surface, another correction must be made to these
data in order to compare the twin small-roll dynamometer data to the
road. In actual operation, tires are not traditionally inflated to 45
PSIG. From tire testing at Calspan's Tire Research Laboratory, it
has been estimated that equilibrium tire rolling resistance is decreased
-------
-19-
by 3% per 1 PSI increased in inflation pressure. Therefore to estimate
actual road tire power absorption and rolling resistance at 26 PSI, a 19
PSI reduction, the mean values of PATN and F in Table 8 would have to
be increased by approximately 57%. u^nis correction was performed on the
data contained in Table 8 and the ratio, RrF> of mean values was recom-
puted to obtain a relationship between the twin small-roll dynamometer
and the road at 26 psi. These results, in addition to the uncorrected
data and the twin small-roll dynamometer data, are presented in Table 9
as a summary of the total correction process and a comparison to the
twin small-roll dynamometer results.
Table 9
Comparison Of Twin Small-Roll Dynamometer Results With
Corrected Single Large-Roll Dynamometer Results At 26 PSI
Tire
Type
Radial
Bias
Twin
Small-Roll
P F
(watts) (Ib/Plb)
Large Roll
Corrected To
Road At
45 PSI
Large Roll Curvature
Corrected To and
Road At Inflation
26 PSI Pressure
(wafts) (Ib^I-lb) (wal?s) (Ib/Plb) Rni7
i_>hi
5721.96 19.282
5212.867 17.567
2168.211 7.306
2545.932 8.579
3404.091 11.470 1.68
3997.113 13.469 1.30
Belted
Bias
5829.297 19.644
3239.604 10.916 5086.178 17.138
1.15
It can be seen from the R,,.., values presented in Table 9 that the basic
assumption of "two on the twin small-roll (at 45 psi) is equal to four
on the road (at 26 psi)" may not be correct. In order for this assump-
tion to be valid, R in Table 9 would have to have a value of two for
all tire types. Since this is not the case, one is lead to believe that
the tires are not completely accounted for on the twin small-roll dyna-
mometer.
In order to completely account for the tires on the twin small-roll
dynamometer, the amount of power absorbed at 50 mph by the tire must be
increased. The amount of increase can be determined from the values of
R . By doubling the value of R in Table 9, the equivalent number of
tires on the road at 26 PSI represented by the power absorbed by the
tire on the twin small-roll dynamometer at 45 PSI may be obtained. By
dividing this quantity into 4, the desired number of tires on the road,
the amount of power absorption increase is obtained. Table 10 presents
the correction factors obtained from the above computations for each
tire type.
-------
-20-
Table 10
Twin Small-Roll Dynamometer Correction Factors
Tire Type Correction Factor
Radial 1.190
Bias Belted 1.534
Bias 1.745
By increasing the amount of power absorbed by the tire on the twin
small-roll dynamometer by the appropriate tire type correction factor,
the basic assumption should be realized. Two possible methods of increa-
sing PATM on the twin small-roll dynamometer are; 1) reduce the test
tire pressure or 2) increase the vertical loading on the tire. The
former suggestion may prove to be hazardous, since tire life may be
drastically reduced when operating at other than 45 PSI inflation pres-
sures. A partial solution may be to increase the dynamometer power
absorber setting to increase vehicle engine loading, however increased
tire slip may result.
V. Conclusions
The results of this experiment make three things evident:
1) The ranking of radial, bias belted and bias ply tires based on
tire rolling resistance is not the same on the small twin-roll dynamo-
meter as it is on the road.
2) The power absorbed by the tire at 50 mph when operated on the
small twin-roll dynamometer at 45 PSIG is not twice that of the same
tire at 26 PSIG operated on the road, as was generally thought to be
true.
3) The rolling resistance of one manufacturer's tires can be
statistically distinguished from another's.
The data presented in this report also indicate several notable
items:
Item 1: Federal emissions and fuel economy testing is conducted on
the small twin-roll dynamometer. This experiment indicates that based
on rolling resistance, the relative rankings of tires with respect to
construction type on the small twin-roll dynamometer may not be the same
as the road (i.e., the relationship between radial and bias belted tires
at 50 mph is, on the average, reversed on the small twin-roll dynamo-
meter). This would imply that a vehicle tested on the dynamometer may
not receive any benefits (or penalties) based on the type of tires on
that vehicle.
-------
-21-
Item 2: Since only the two driving tires are operated on the
dynamometer, twice the road power should be absorbed to account for the
two non-driving tires not on the dynamometer. The data presented indi-
cates that this is not occuring. This implies that an adjustment
(increase) to the amount of power absorbed by the tires should be made
when testing a vehicle on the twin small-roll dynamometer.
Item 3: When a vehicle is certified for production by the EPA, the
manufacturer of the tires supplied on the test vehicle is not specified.
As can be seen from the analysis above, the tire manufacturer has an
effect on the tire rolling resistance and therefore the vehicle's
emissions and fuel economy. It is common practice for a vehicle manu-
facturer to have several manufacturers for the same tire. This fact
leads to the conclusion that a vehicle manufacturer could take advantage
of the federal tests by supplying a vehicle with tires of the lowest
rolling resistance available, certify and not bother equipping the
production vehicles with the same tires (same size, but not the same
manufacturer).
VI. Recommendations
It is obvious from the data presented that tires on the Clayton
dynamometer do not exhibit the same power absorption characteristics as
on the road. Assuming the approximations in Table 9 are reasonably
accurate, it would appear that the Clayton dynamometer does a fair job
of duplicating the road for the case of radial tires. However, for bias
belted and bias ply tires, the Clayton does not do as well. Further
tire testing at an initial cold pressure of 26 PSI is currently underway
to verify the results of Table 9. For if true, the result of this
report indicate that either a correction factor should be added to the
Federal Test Procedure to account for tire differences or that the
Clayton dynamometer should be replaced or altered. The idea of a cor-
rection factor is obviously the more cost effective. One suggestion to
this end, is to decrease the test tire pressure by an appropriate per-
centage based on tire type to force the basic assumption for the tires
provided as standard equipment on that vehicle at the recommended tire
pressure. This type of correction assumes that the difference in power
absorbed at 50 mph displayed in this experiment is constant throughout
the Clayton power absorption curve and that the tires are in a state of
equilibrium. It is recommeded that tire power absorption character-
istics be investigated at other discrete speed intervals in order to
make this determination.
The fact that the tire manufacturer had an effect on the power
absorbed by the tire at 50 mph would tend to indicate that EPA should
specify the tire to be installed on each vehicle from among those tires
to be installed in production.
-------
-22-
REFERENCES
1. Schuring, "Rolling Resistance of Tires Measured Under Transient and
Equilibrium Conditions on Calspan's Tire Research Facility." DOT-
TSC-OST-76-9, March 1976.
2. Crum, W.B., "Road and Dynamometer Tire Power Dissipation," Society
of Automotive Engineers, SAE 750955.
3. Schuring, D.J., "The Energy Loss of Tires on Twin Rolls, Drum,
and Flat Roadway - A Uniform Approach," Society of Automotive
Engineers, SAE 770875.
4. Clark, S.K.; Dodge, R.N.; Banter, R.J.; and Luchini, J.R.; "Rolling
Resistance of Pneumatic Tires," University of Michigan Report DOT-
TSC-74-2; Prepared for The Department of Transportation, Transportation
Systems Center, Cambridge, Mass., July 1974.
5. Curtis, W.W., "Low Power Loss Tires," Society of Automotive Engi-
neers, SAE 690108.
6. Elliott, D.R.; Klamp, W.K.; and Kraemer, W.E., "Passenger Tire
Power Consumption," Society of Automotive Engineers, SAE 710575.
7. Floyd,.C.W., "Power Loss Testing of Passenger Tires," Society of
Automotive Engineers, SAE 710576.
8. Clark, S.K., "Rolling Resistance Forces in Pneumatic Tires,"
University of Michigan Report DOT-TSC-76-1; Prepared for The
Department of Transportation, Transportation Systems Center,
Cambridge, Mass., January 1976.
9. Thompson, G.D., "Light-Duty Vehicle Road Load Determination,"
Technical Support Report for Regulatory Action, LDTP-76-03,
December, 1976.
-------
APPENDIX A
PLOTS OF P AND F VERSUS DYNAMOMETER TYPE
K_K
AND FDB VERSUS TIRE TYPE FOR EACH DYNAMOMETER TYPE
RK
-------
.= ( 1 000 ,
(o ,3)
SCATTER PLOT HOE:
9nno.o
370 -
8111.1 *
H
I
i
° 6333.3
3
16B/020/12B - 3,
420/16B - c
240 -
370 -
16A -
260 -
310 -
400/420/240 - 3.
230/12B/080/260/400 -
300/310/290 -
080/020/250/230/200 -
300/210 - 2
070 -
220 -
270/300/250/270 -
020/180/310 -
250 -
200 -
P777.R
I
o >
H I
03
(D
'a - 300/020
- 310/250/16B/180
- 16A/16B/080/310
- 12B/400/370/290
- 240/230
3 - 12B/300/12B
- 260
- 270/370/300
- 270/250/220/080
- 250/250/260
- 310/420/200/240
- 420
- 230/210
- 310/020
- 220/070
- 200
inoo.o
0.
CL
DYNO TYPE CODE
ELECTRIC
-------
SCATTER PI.OT
PATV(inflTTS)
9000.0
-> T!C.:f TYPR:nl-'-s
T r s
6333.3
340/340 -
340 - »>.
3666.7
2777.
320/320 -
060 - «
* - 330
- 340/330/340
d -340/330
'* - 060
'2 - 320/320
'« - 320
- 060
p>
00
SP
180P.Q
1000.0 *
0.
1
t. YfO!
OYNO TYPE CODE
ELECTRIC
-------
PLOT <-» TUP.
PATN(WATTS)
SOOO.O +
410 - --
f* 111.1 +
6133.
s
g
S 3*66.7 *
2777.fi +
350 -
13A -
- 410
2 - 13A/350
8 |
H pd
O
ra >
i
HI 10
O
H
rt
H-
i
a>
- 13A
10 f) 0 . n *
0.
1
CLAYTON
2
ELECTRIC
DYNO TYPE CODE
-------
TTOK TYP£:Pfi'JJ. Al_
30.000 *
<0»3» >
?3.3!3 »
13.333
in.ono +
6.66*7 +
*
3
S
2
4
4
*
3
4
4
3
2
3
2
3.3333 *
0.
0.
1
Cl AYTON
2
ELECTRIC
OVWO TYPE CODE
-------
SCATTER PLOT «<> TI-E
FRR
3n.0')n *
20.000
CO
o
g
13.3T3
10.000
it
2
3.3333
0.
DYNO TYPE CODE
Cl
ELECTRIC
-------
SCATTKP PLOT
FRR
3 o. o n o
>!-. TYPh : - f a'-
?3.3'n
^ n. o f i o
CQ
1
9
w
u
I
CO
c
rr
ID
i-l
13.3^3
. 0 o n
0.
0.
DYNO TYPE CODP
CLAYTON
ELECTRIC
-------
SCATTER PLOT <1> DYNO TYPE:CLAYTON
FRR(LB/K-LB)
30.000 +
36.667 *
23.333 *
20.000 +
3
4
4
5
2
16.667 *
en
a
o
z
M
13.333 *
10.000
6.6667 *
3.3333 *
3-
II
5
0.
RAOlAL
BI»S BELTFD
5
BIAS
TIRE TYPE CODE
-------
SCATTER PLOT DYMO TYPE:ELECTRIC
FRRCLB/K-LB)
30.000 +
26.667 »
23.333 *
20.000 *
»
»
i~*
3
i 16.667 +
s5- »
| 13.333 *
g ^
3 *
B 5 2
H 2 «
S 4 »
10.000 » A o
3
6.66b7 + 2
3
2
+ «
3.3333
B
oo
0.
0. 145 TIRE TYPE CODE
RADIAL BIAS BELTED BIAS
-------
APPENDIX B
PLOTS OF PATN VERSUS MANUFACTURER
FOR EACH DYNAMOMETER BY TIRE TYPE
-------
SCflTTLP Pi (VI
PAT'jt'-. ATTS)
^000.0
=t- : -. !.,-<-,= ,, : 1 , v -' i .--'.' ; r . - i i ! ' %';.' i :(« --! >
.;: CL-'.VT ) . ". bh s = TT - T , -'i :'.{ .
«1 1 1 . 1
»-370
01
-s
o
-020
6333..1
-080
-080/020/250/200
-070
-220
-250
-020
-250
-200
-16B/12B
-420/16B
-16A
-240
s, -260
,-: -400/240
^ -260/400
-:: -300
,- -300/210
« -300
a -370
* -310
i -310/290
n -270/270
f. -180/310
-230
-230
3A66.7
g ?
MI i-i
C H-
n N
ft) (D
B"
o. >
H- cr
to
' O
&B
I-1 O
I rt
SO H-
O O
!- 3
I
00
5
ID
^777. f
1000.0
o.
V. l|):":Vt I-
FIPrSTONE
MANUh ACTUr(ER
Tire Manufacturer
-------
SCATTfc-W PI OT
P4T*! (WATTS)
9000.fi
tLrCT-'IC '"":!: <; = T ?'!' IYJr:^;''il
Iz
(D O
o y
rt a
C m
1-1 I-1
(0 H-
CO
a
CO
g-e
< o
IH 01
^555.
eg
1-1
IB
B)
1
3
00 >
o
a)
§.
2777.
,!. -020
» -250
., -080
< -250/220/080
,. -250/250
-:- -200
-020
-220/070
-200
* -16B
r -16A/16B
:: -12B
v -12B/12B
» -420
:t -420
« -300
» -400
* -240
« -300
^ -260
» -300
ft -260
« -240
ft -210
a-310/180
o-310
,?-370/290
2-270/370
o-270
o-310
» -230
" 6
OQ P
(0 O
I rt
I-- O
t->
O
fill
H
to H-
3 t-t
o n
» -230
inoo.n
0.
GOi; -i- 1C'
FI»ESTONE
Tire Manufacturer
lANUFACTUrtER
GENEKAL
-------
:( 0 .'
SCATTER PLOT
PATM(«IATTS)
'JOOO.O
<1> D/WO:
'-.aSf- >=7I-<- 7YPt.:-.TAS .-^
7222.?
6333.3
?-340/340
«-340
* -330
» -330
* -330
a
a
g-s
< o
CU CD
4555.ft
-320/060
; -320/320
-> -060
H- >
era
c
a
ci
3666.7
2777.fi
1000.0
PIPESTONE
MANUFACTUKEH
GENEHAL
Tire Manufacturer
-------
PLOT <:->
wATTM
9000.(i +
:-M.): e.LfCT---!C
rt111 . ] +
6333.3
id
i
o
ta
g-B
r>
c ?
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H- (0
H O.
(0
f
00
o
(- O
i-1 i-n
era
I
1888.9
1000.
> i'.> Ul-IHOYAL.
Tire Manufacturer
FIHESTONE
MANUFACTUkER
-------
PLOT
PAT>;< WATTS)
9000.0
!'>YVO: CL«YT'
Tr-'J.
-410
7?;??.'
6333.3
--13B
^-350
C Hi
H M
(II H-
1 N
ID
g,0.
a
s,
o
DO
C
n
l-l
I
PH
a
a)
-13A
3666.7
2777.« *
Is
H1 O
I-- 3
(-
O
1000.0 +
<
(1.
i jit- ''!' ' !' I Woy ,,[_
Tire Manufacturer
^ I REST ONE
ACTUKER
-------
-* Pi OT < > }*< '>: f L ?.'.'..
K-47TS)
* n o o. o +
c. Ill . I
a
I
a
a)
-s
o
o
rt tl
C P
1-1 5
n> M
n H-
M
"3
O) O
H- S
t» ro
a> n
ha >
I-1 a"
^§
S3-
n n>
n> a.
IB
3 >
era to
sr?
1 3
rt
I H-
ta o
5 s
H-"
I-- O
aa
S
n>
T
?7 /7.P
« 13A
1000.0
! I 1 I r -T i 1,
Tire Manufacturer
&CTURER
-------
APPENDIX C
DESCRIPTION OF TEST TIRES BY IDENTIFICATION NUMBER
-------
C-l
Tire Description
ID Number
Manufacturer
020
060
070
080
12B
13A
13B
16A
16B
180
200
210
220
230
240
250
260
270
290
300
310
320
330
340
350
370
400
410
420
Goodyear
Goodyear
Goodyear
Goodyear
B.F. Goodrich
B.F. Goodrich
B.F. Goodrich
B.F. Goodrich
B.F. Goodrich
Firestone
Goodyear
Uniroyal
Goodyear
General
Uniroyal
Goodyear
Uniroyal
Firestone
Firestone
Uniroyal
Firestone
Goodyear
Uniroyal
Firestone
Uniroyal
Firestone
Uniroyal
B.F. Goodrich
B.F. Goodrich
Size Model
BR 78x13 Polyglass Radial
H 78x15 Custom Power Cushion Polyglass
HR 78x15 , Polyglass Radial
HR 70x15 Polyglass Radial WT
HR 78x15 Steel Radial Silvertown
H 78x15 Custom Long Miler
H 78x15 Custom Long Miler
HR 70x15 Silvertown Lifesaver XL-100
HR 70x15 Silvertown Lifesaver XL-100
GR 78x15 Steel Belted Radial
HR 78x15 Steel Belted Radial Custom
Tread
GR 78x15 Steel Belted Radial PR6
GR 78x15 Steel Belted Radial Custom
Tread
GR 78x15 Dual Steel II Radial
LR 78x15 Steel Belted Radial PR6
ER 78x14 Steel Belted Radial Custom
Tread
FR 78x14 Steel Belted Radial
FR 78x14 Steel Belted Radial
HR 78x15 Steel Belted Radial
ER 78x14 Steel Belted Radial
ER 78x14 Steel Belted Radial
E 78x14 Custom Power Belted Cushioned
Polyglass
E 78x14 Fastrak Belted
E 78x14 Sup-R-belted Deluxe Champion
B 78x13 Fastrak Belted
BR 78x13 Steel Belted Radial
HR 78x15 Steel Belted Radial
B 78x13 Silvertown Bias
GR 78x15 Lifesaver 78 Steel Belted
Radial
-------
APPENDIX D
NORMALIZED TEST RESULTS AT 50 MPH BY TIRE IDENTIFICATION NUMBER
-------
TABLE D-l
NORMALIZED TEST RESULTS BY TIRE IDENTIFICATION NUMBER
TIRE
ID
270
020
260
250
020
310
300
020
370
370
310
300
26 0
25 0
16H
220
420
16A
230
080
210
180
290
12H
400
400
200
070
250
240
300
310
270
240
16B
128
200
230
420
080
300
020
270
310
250
260
370
020
TEST
DYNO
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
I
1
1
1
1
2
2
2
2
2
2
2
2
DYNO
HP-
SET
5.9
5.9
5.9
5.9
5.9
5.9
5.o
6.8
6.8
7.4
7.4
7.4
7.4
7.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
10.5
10. 5
10.5
10.5
10.5
10.5
10.5
5.9
5.9
5.9
5. «
5.9
5.9
6. P
6.8
MFR.-
CODE
4
1
3
1
1
4
3
1
4
4
4
3
3
1
?
1
2
?
5
1
3
4
4
2
3
3
1
1
1
3
1
4
4
3
?
2
1
5
p
]
3
1
4
4
1
3
4
1
ROLLING
FORCE
(NT)
214.263
318.867
277.830
242.089
211.985
271.225
248.923
243.519
292.339
375.867
247.8?.!
236.793
254.925
214.421
306.953
222.740
266.534
286.363
259.631
244.348
236.157
209.757
247.647
316.487
266.574
253.768
193.477
228.500
206.359
305.471
217.997
209.629
218.589
262.152
319.058
2S9.784
241.231
241.985
312.521
255.517
130.734
161.452
114.163
100.672
104.248
123.708
118.062
79.770
ROLLING
RESISTANCE
(LB/K-LB)
16.138
24.016
20.925
18.233
15.996
20.428
18.748
18.34]
22.018
28,309
18.665
17,834
19.200
1^.149
23.119
16.776
20.074
21.56P
19.570
18.403
17.787
15.79P
18.652
23.P37
20.077
1 9 . )1 3
14.572
17.210
15.S42
23.007
1^.419
15.789
16.463
19.744
24.030
19.<=66
18.169
18.225
23.53?
19.245
9.846
12. 160
8.598
7,58?
7.852
9,317
8.892
6.008
POWER
ABSORBED
AT 50 MPH
(WATTS)
4788.777
7126.680
6?09.500
5410.638
4746.770
606! .879
5563.430
5442.641
6*33.781
8400.617
553**. 844
5?9?.324
5697.574
479?.309
6«.6i).398
4976.238
5Q57.035
6400.215
5907.223
5461. .180
5?76.109
468R.070
5*34.910
7073.484
5957.930
5671.715
4324.21 1
5106.977
46]?. 125
6«27.277
487?. 234
4685.207
4885.465
5P5>.098
713H.945
^06.172
5391.512
540?:. 363
6984.844
57ir>.805
2921.905
3608.446
2551.543
2?5f>.019
2329.943
2764.874
2*3P.676
1782.857
-------
TABLE D-l cont.
TIRE
ID
260
370
250
310
300
250
300
16H
200
210
230
080
250
220
240
400
310
310
220
16A
12R
290
180
070
420
080
200
168
128
12B
420
240
230
270
340
330
320
320
340
330
320
060
340
330
060
320
330
340
TEST
DYNO
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
1
1
2
2
2
HP
SET
7.4
7.4
7.4
7.4
7.4
7.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.4
8.^
8.4
8.4
8.4
8.4
8.4
8.4
10.5
1 0 . S
10.c
10.5
10. S
10.5
10.5
10. 5
8.4
5.9
5.9
5.4
7.4
7.4
7.4
8.4
8.4
8.4
8.4
10.5
5.9
5.9
5.9
MFR
CODE
3
4
1
4
3
1
3
2
).
3
5
1
1
1
3
3
4
4
1
?
-j
4
4
1
?
1
I
2
2
2
2
3
5
4
4
-)
]
1
4
3
1
I
4
3
1
1
1
4
ROLLING
FORCE
(NT)
102.725
141. blS
110.563
147.946
115.121
106.932
167.087
157.663
65.146
84.118
85.028
151.477
159.039
109.334
94.924
143.499
160.403
80.645
74.114
152.359
131.699
141.404
154. 38S
71.770
88.346
108.150
96.650
151.719
130.598
146.005
98.388
138.981
134.572
119.187
278.243
250.34*
216.169
195.912
271.722
227.369
196.342
215.197
276.695
246.406
191.215
120.146
155.767
154.410
ROLLING
RESISTANCE
(LB/K-LB)
7.737
10.681
«. 327
11.143
H . 6 7 1
6.054
12.584
11.675
4.907
6.335
6.404
11.409
11.978
8.235
7.]49
10.808
12.08].
6.074
5.582
11.475
9.919
10.650
11.628
5.405
6.654
8.145
7.279
11.427
9.836
in. 997
7.410
10.46P
10,136
8.977
20. -956
18.855
16.281
14,755
20.465
17.125
14.788
16.208
20.840
18.558
14.402
9.049
11.732
11.630
POWER
ABSORBED
AT 50 MPH
(WATTS)
2P9S.904
316^.557
2471.083
3306.593
2c;7?.954
2389.930
3734.394
3^23.768
1456.013
1&80.037
1900.376
33BS.511
3554.522
2443.615
2121.551
3207.203
3^85.007
1P02.416
1656.448
340S.224
2943.473
3160.379
3450.505
1604.059
1974.533
2417.152
2l6f . 127
3390. 920
2918.865
3263.212
2198.972
3106.225
3007.684
2663.830
6?lfl.730
559S.277
4831.379
4378.633
6n7?.988
5081.695
4388.242
4R09.652
6184.133
5507.176
4?73.656
268S.263
3481.392
3451 .063
-------
TABLE D-l cpnt.
TIRE
ID
340
320
330
330
340
060
320
060
410
350
350
410
13A
13B
13A
350
350
410
410
350
410
13A
13*
13A
TEST
DYNO
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
DYNO
HP
SET
7.4
7.4
7.4
8.4
8.4
8.4
8.4
10.5
5.9
5.o
5.4
7.4
8.4
8.4
10. b
7.4
5.o
5.9
7.4
7.4
7.4
8.4
8.4
10.5
MFR
CODE
4
1
3
1
4
I
1
1
?
T
3
2
?.
2
?.
3
i
p
?
3
?
2
2
2
ROLLING
FORCE
(NT)
144.461
121.398
141.334
192.077
159.679
129.896
125.506
105.717
263.859
202.45?
251.830
366.373
223.471
303.90ft
167.927
306.732
208.536
247.276
181.753
153.007
1*4.479
1 10.581
152.202
212.003
ROLLING
RESISTANCE
(LB/K-LB)
10.R80
9.143
10.645
14.467
12.026
9.783
9.453
7.962
19.873
15.248
18.967
27.594
16.331
22.889
12.648
23.11)2
15.710
18.624
13.6.89
11.524
12.38P
H.329
11.463
15.967
ABSORBED
AT 50 MPH
(WATTS)
3?2«.703 1
2713.245
3158.815
4?92.922
356R.826
2^0 ''..I 76
2^05.059
2362.775
5P97.258
4S24.801
562H.402
8188.441
4094.578
6792.301
3753.168
6«55.453
4661.898
5526.621
4062.173
341Q.715
3676.104
2471 .485
3401.715
473H.266
Test Dyno Code Manufacturer's Code (MFR)
1 = Clayton 1 = Goodyear
2 = Electric 2 = B. F. Goodrich
3 = Uniroyal
4 = Firestone
5 = General
-------
APPENDIX E
UNLOAD AND LOAD TIRE RADII BY TIRE IDENTIFICATION NUMBER
-------
E-l
Tire ID
Number
020
060
070
080
12B
13A
13B
16A
16B
180
200
210
220
230
240
250
260
270
290
300
310
320
330
340
350
370
400
410
420
Tire
Radius at 45 PSIG (Meters)
Size
BR78
H 78
HR78
HR70
HR78
H 78
H 78
HR70
HR70
GR78
HR78
GR78
GR78
GR78
LR78
ER78
FR78
FR78
HR78
ER78
ER78
E 78
E 78
E 78
B 78
BR78
HR78
B 78
GR78
x 13
x 15
x 15
x 15
x 15
x 15
x 15
x 15
x 15
x 15
x 15
x 15
x 15
x 15
x 15
x 14
x 14
x 14
x 15
x 14
x 14
x 14
x 14
x 14
x 13
x 13
x 15
x 13
x 15
Unloaded
.305
.362
.355
.361
.354
.367
.365
.375
.373
.346
.354
.345
.349
.348
.365
.326
.333
.329
.354
.328
.325
.334
.331
.333
.310
.301
.355
.304
.349
Loaded
.298
.349
.344
.348
.343
.351
.355
.361
.364
.333
.341
.334
.334
.336
.353
.311
.318
.318
.341
.315
.312
.319
.318
.321
.302
.295
.344
.300
.337
-------
APPENDIX F
PLOTS OF P VERSUS DYNAMOMETER HORSEPOWER SETTING
AJLIN
BY TIRE SIZE AND TYPE FOR EACH DYNAMOMETER
-------
TT YPE tRADI AL*TSUE : 13" CflSES=DvKjO : CLAYTO
N= 5 OUT OF 5 6.PATN VS. 4. HP
PATN
8500.0 +
« -370
7555.6 *
-020
6611.1 +
» 5666.7
4-1
CO
I
° 4722.2
4-1
ffl
< 0)
* -8
O
0)
3777.8
2833.3
1888.9
944.44
13" Radial Ply Tires
At 45 PSI
-370
»-020
» -020
3 ID
tre n
n g
H-1 1
-< ac
H >
ID O
01
n>
T3
1
ro n
H
era
c
ro
'ri
0.
4.0000
5.5556
4.7778
7.1111 8.6667
7.8R8'»
Dynamometer Horsepower Setting
10.222
9.4444
HP
11.000
-------
:4 CASFS=V1:2 STRAT=V2: 1«V 7: 1 li-ire.PVAL= (0 ,8500 ) ; (4t
SCATTER PLOT <1> TTYPRtRADI AL*TS t tt.: 13" CASt"S = 0 /MO: f-
M= 4 OUT OF 4 h.PATN VS. 4.HP
PATN
8500.0 +
7555.
13" Radial Ply Tires
6611.1 * At 45 PSI
^5666.7
§3777.8 +
S « -020
-370
»-370
1888.9 +
» -020
944.44 +
0.
4.0000 5.5556 7.1111 8.6667 10.222 HP
4.7778 6.3333 /.8n89 9.4444 11.000
Dynamometer Horsepower Setting
-------
SCATTER PLOT <1> Tl YPFtRADI AL^TSI/t: 14" CftSf 5=nvMo:CLAYTO
N= 13 OUT OF 13 6. PAT" Vs. 4. HP
PATN
8500.0 *
7555.6 *
u 5666.7
2-260/310
o -300
« -250
14" Radial Ply Tires
At 45 PSI
-> -260
« -310
<> -300
rt O
H- 6
a m
m *
-p- o*
= re
D-
o
u 4722.?
~270
* ~250
2 -270/300
* -310
» -250
H >
3777.8
H ft
P* H-
ft> O
-------
TTyPF :RAOI AL«TSI ?E : 14" C",SF.S=UvNO : F
N= IB OUT OF 15 6. PATH Vs. 4. HP
PATM
8500.0 +
755S.6
6611.1
ro
rt O
H- S
9 1C
OP ^
14" Radial Ply Tires
At 45 PSI
H 01
o
M 1-1
b666.7
B >
a. rt
I
<
0)
< o
PM co
£ 3777.8
* -300
2 -310/250
»-310
n> o
3
cn
H- o
O MI
oo
(- o
(D ><
2833.3
1888.9
« -300
« -260
» -270
« -250
« -310
-300/250
-250/260
-270
-310
I rt
\a ID
o 4
M
!- 3!
O
U 4
V! (D
° 5
9 O
O S!
944.44
0.
4.0000
5.555* 7.1111
4.777R 6.3333 7.8889
Dynamometer Horsepower Setting
.8.6667
10.222
9.4444
HP
11.
000
-------
=6:4
ST^AT=V2 : 1
Krn/AL= ( 0 . 3500 > ; (4» 1 1 > >
SCATTER PLOT <1> TTYPF :RADI AL^TSI^E: 15" CASES=OvNO:CLAYTO
N= 2?. OUT OF 23 6.PAT'J Vs. 4. HP
PATN
P500.0 +
7555.6 +
15" Radial Ply Tires
At 45 PSI
6611.1 *
rt 5666.7
S!
4722.2
o
0)
e-s
< o
OH 01
£ 3777.8
3
o
PM
O
O D-
H 01
O
01 >
O. rt
I-1 O
33
ro
01
"3
§>§
O
> H*
n>
2833.3
18afl.9
o ae
^ s
II
§ §
rr (0
a H
944.44
0.
4.0000
5.555ft 7.H11
4.7778 6.3331 7.6889
Dynamometer Horsepower Setting
8.6667
10.222
9.4444
HP
11.000
-------
-, w," Hw .),.-,-,. , t.3. v «,-,.
PATN
8500.0
7555.6 «
6611.1
5666.7
15" Radial Ply Tires
At 45 PSI
4722.3
o
HI
g-a
< o
PL, 10
-------
N= 9 OUT OF 9 6.PATN VS. 4. HP
PATN
8500.0 +
7555.6 *
14" Bias Belted Tires
At 45 PSI
6611.1
« 5666.7 *
1
o
< 4722.2 +
T)
en i
"d >
o o-
n to
o
I-1 1
*- o-
: ro
ex.
ca
H- >
[U rr
n
Ln
to O
ID
R>
O.
(D Tl
0§
? O
rt
3?
n> o
00
c
o
a)
N
2833.3
50 rt
o ro
1888.9
rt
ro
i-t
-o
o
(D
944.44
0.
4.0000 5.5556 7.1111 8.6667 10.222 HP
4.7778 6.3331 7.8889 9.4444 11.000
Dynamometer Horsepower Setting
-------
I it A. /'i.Wi -4 * . . . - - ~ -i'i_i.-_ . - . i, :. o
N= 9 OUT OF 9 6.PATN VS. 4.HP
PATN
8500.0 »
7555.6
i!
o
o
0)
-s
o
T3
01
N
6611.1 +
5666.7 »
4722.? *
3777.8
g 2833.3 +
14" Bias Belted Tires
At 45 PSI
s
2 -330/340
-320
-340
-330
-320
.-330
-340
-320
en
(B
It
rt >tf
P- O
o e
no n>
CO
K-1 O
S O-
n>
ca o.
H-
01 >
w rt
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4.7778 6.3333 7.8889 9.4444
10.222 HP
11.000
Dynamometer Horsepower Setting
-------
i i-rt " WN. i '- . > , . I ." ,1 C. .HO-" .1 . J . <- v . 3
N= 2 OUT OF 2 6.PATN VS. 4.HP
PATN
8500.0 +
7555.6 +
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5666.7 +
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4.0000 5.5556 7.1111 8.6667 10.222 HP.
4.7778 6.3333 7.8H89 9.4444 11.000
Dynamometer Horsepower Setting
-------
N= t. UUr
PATN
8500.0 +
7555.6 +
en
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2833.3 +
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4.7778 6.333T 7.B889 9.4444 11.000
DyiuiniiMiirl "8
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11
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1888.9 + S "
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N= 5 OUT OF 5 6.PATN VS. 4. HP
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8500.0 +
7555.6 «
tt -410
6611.1 »
5666.7 »
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13" Bias Ply Tires
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5.5556 7.1111 8.6667
6.3333 7.BH89
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9.4444 11*000
Hrv-roonnunr R
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SCATTtR PLOi t i V^t :b»Mi>w i bite. i j - vH3ra-uiwiiti.ui.irt
N= 5 OUT OF 5 6.PATN VS. 4.HP
PATN
8500.0 *
7555.6
6611.1
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5666'7
13" Bias Ply Tires
At 45 PSI
.-wo
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3777.8
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1888.9
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4.0000 5.555ft 7.1111 8.fc667 IO.ZZ2 HP
4.7778 6.3331 7.8rtH9 ' 9.4444 11.000
-------
PATN
8500.0
3 OUT OF 3 6.PATN VS. 4. HP
7555.6
6611.1
15" Bias Ply Tires
At 45 PSI
»-13B
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2833.3
1888.9 +
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ID ID
it ft
0. + . .
4.0000 5.5556 7.11H 8.6667 10.222 HP
4.777fl 6.1333 7.8B89 ' 9.4444 11.000
Dynamometer Horsepower Setting
-------
SCATTER PLOT i i Yh't :biHS* i iitr.. «ivl Ltt'ar 3=i>«iW '.cut-
N= 3 OUT OF 3 6.P4TN US. 4.HP
PATN
8500.0 +
7555.6
6611.1
to
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'w 5666.7 +
15" Bias Ply Tires at 45 PSI
g.
35
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PL, W
H
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2B33.3
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t/3 h1*
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fl 3
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^ CB
CJ o
1888.9
4.0000 5.5556 7.1111 8.6667 10.222 HP
4.777« fc.3331 7.8«89 9.4444 11.000
Dynamometer Horsepower Setting
------- |