LDTP 78 - 02
Technical Report
Tire Slip on the Clayton Dynamometer
by
Richard Burgeson
Myriam Torres
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 considerations or data received subsequent
to the date of release of this report may alter the conclusions reached.
Readers are cautioned to seek the latest analysis form 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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-1-
I. Introduction
Tire rolling resistance measurements at a steady state 50 mph were
conducted on the Clayton dynamometer during a recent tire/dynamometer
roll interface effects program. These measurements required the collection
of front and rear roll speed data. Analysis of these data indicated
that the front roll consistently revolves more slowly than the- rear
roll. For the purposes of this report, this roll speed difference was
defined as "tire slip".
/
Power from the vehicle is transferred to the dynamometer primarily
through the front roll, since the power absorption unit and inertia
simulation assembly are connected to this roll. The rear roll remains
free to revolve independently and is traditionally used to estimate
"true" vehicle speed. The difference in roll speed displayed throughout
this experiment may be caused by tire deformation (e.g., different
rolling radii), tread creep, tire slippage or some other unidentified
phenomenon due to the loading applied by the front roll. Analyses of
these difference data were conducted to determine if the tire slip is
influenced by dynamometer horsepower setting, tire type, tire size and
manufacturer.
II. Summary/Conclusions
As part of the tire/dynamometer roll interface effects project, front
and rear dynamometer roll speed data were collected during tire testing.
A total of 88 steady-state (50 mph) tests were conducted on radial, bias
belted and bias ply tires under five (5) dynamometer horsepower setting
conditions. Initial analysis indicated that the front roll consistently
revolved at a slower rate than the rear roll. This difference in roll
speed may be due to tire deformation, actual tire slip, tread creep or
some other unidentified phenomenon and for the purposes of this report
is defined as "tire slip".
The basic design of the Clayton dynamometer utilizes the front roll as
a conductor of power, transmitted from the vehicle to the dynamometer.
The combination of the small surface area of the roll and the relatively
small tire-contact-patch, causes an unnatural tire footprint on the roll
during load application. These conditions result in the difference in
roll speed detected during this experiment.
By expressing the "tire slip" as a percentage of the rear roll speed,
the data could be analyzed with respect to dynamometer horsepower
setting, tire type, tire size and manufacturer without regard to any
speed differences which may have occurred.
Analyses of these data indicated that the percent slip is significantly
affected by horsepower setting, tire size and type. It was found that:
1) the percent slip increases with increasing horsepower setting; 2) 14
inch tires slip less than both 13 inch and 15 inch tires and that the 13
inch tire slips more than the 15 inch tires; and 3) that radial tires,
in general, have significantly higher slip characteristics than either
bias belted or bias ply tires.
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-2-
It was concluded that "tire slip" causes the dynamometer to underload a
test vehicle. The magnitude of this underloading is a function of tire
type, tire size, manufacturer and dynamometer horsepower setting. In
general, for a vehicle equipped with radial tires travelling at a
velocity of 50 mph, it can be estimated that the underloading could be
as high as 0.34 Hp. This is based on the premise that the amount of
power absorbed by the Clayton dynamometer is proportional to the third
power of the front roll speed. The magnitude of the "tire slip" under
transient testing conditions is not yet available.
III. Technical Discussion
A. Program Objectives
1. Determine the magnitude of the tire slip during a steady state
speed condition.
2. Determine the effects of tire type, tire size, tire manufac-
turer and dynamometer horsepower setting on tire slip.
B. Program Design
A total of 88 steady state tests (50 mph) were conducted on one
twin roll (Clayton) dynamometer utilizing two vehicles. Data were
collected on radial, bias belted and bias ply tires under five (5)
conditions of dynamometer horsepower setting. The front and rear roll
speeds during each test were monitored and recorded on 7-track magnetic
tape at a rate of once per second. After tire temperature stabiliza-
tion, data were collected for approximately five (5) minutes.
C. Equipment
1. Vehicles - Two vehicles were utilized during this study, a 1971
Ford stationwagon and a 1971 Vega stationwagon. Tires with nominal
sizes of 14" and 15" were mounted on the Ford for test and those with a
nominal size of 13" were mounted on the Vega.
2. Dynamometer - All tests were conducted on one (1) standard
Clayton twin roll dynamometer with 8.65 inch diameter rolls which were
spaced 17.25 inches apart. Each roll was equipped with a magnetic
proximity pick-up and the frequency at which each individual roll revol-
ved was monitored simultaneously. Approximately 300 data points per
test were collected.
3. Data Collection - A Kennedy Company 7-track tape recorder was
utilized in conjunction with a Datum digital data acquisition system to
record front and rear roll speeds, a tire type code, a test identifica-
tion code, a tire manufacturer code and a tire size code. In addition,
initial (cold) tire pressure and dynamometer road load horsepower set-
ting were recorded manually on data sheets. Data recorded on magnetic
tape were taken at a once-per-second rate.
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_ 3—
D. Analysis
Initially, the mean front and rear roll speeds were computed for
each test. The results indicated that the front roll consistently
revolved more slowly than the rear roll. The difference, which for the
purposes of this report was defined as "tire slip", may be due to tire
deformation, tread creep, actual tire slippage or some other unidentified
phenomenon caused by the vehicle loading function of the front roll.
The difference between each front and rear roll speed mean value
was then expressed as a percentage of the rear roll speed mean. The
mean value of the rear roll velocity was selected because it is assumed
to be representative of true ground speed. Equation 1 summarizes the
computation for each test:
V - V
— — x 100% = % slip (1)
V
rr
where V = mean rear roll speed
rr
V,. = mean front roll speed.
The mean front roll speed was subtracted from the mean rear roll speed
strictly for convenience.
The percent slip was then statistically tested for effects due to
dynamometer road load horsepower setting, tire type, tire size and tire
manufacturer.
E. Test Procedure
The data for this report were generated as part of the tire/dynamo-
meter roll interface effects test program for which the power absorbed
by the tire was measured on two types of dynamometers, a twin roll
Clayton and a large (48") single roll electric. Briefly, a set of test
tires was installed on a particular test vehicle and the vehicle was
accelerated to a speed of 50 mph and maintained at that speed for 20
minutes. Vehicle transmitted-power and dynamometer received-power data
were collected during the entire 20 minute period. The data generated
on the twin roll (Clayton) dynamometer were analyzed for roll speed dif-
ferences in this report. Only roll speed data collected after tire
warm-up (15 minutes) were utilized for this analysis.
IV. Results
There were four factors recorded that were either suspected to have or
were analyzed to determine if they have an effect on tire slip. These
factors are: tire type, manufacturer, tire size and dynamometer horse-
power setting. In order to determine if any one of these factors
affect tire slip without an interaction with one or more of the re-
maining factors, two-way frequency tables were generated and Chi-square
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-4-
tests for independence were performed for all possible factor combina-
tions. These tests would determine whether the sample was randomly
distributed across the four factors. It was found that both tire type
and manufacturer were randomly distributed with respect to dynamometer
horsepower setting. Therefore, any effects attributed to horsepower
setting would not be Influenced by either tire type or tire manufac-
turer. However, it was found that the other factors (tire type, size
and manufacturer) were not randomly distributed with respect to each
other. Subsequent analyses investigating the effects of the above
factors take this fact into account. The findings of this investigation
are presented below for each factor.
A. Dynamometer Horsepower Setting
To more accurately simulate on the dynamometer the experience of
the tire on the road, a higher dynamometer road load horsepower setting
was applied to the larger tires of the sample, since they are typically
installed on larger and heavier vehicles. This practice explains the
interaction effects of the sample distribution found in the preliminary
analysis. In order to isolate any influence tire size may have on slip,
analyses of variance were conducted on the percent slip with respect to
horsepower setting for each nominal tire size. Figure 1 is a typical
plot of the percent slip versus dynamometer horsepower setting for 14
inch tires (for additional plots see Appendix A).
The results of the analyses indicated that horsepower setting has
a significant effect on tire slip. For each tire size, tire slip in-
creases as the dynamometer horsepower setting increases. As an example,
Figure 2 shows the mean percent slip with respect to dynamometer horse-
power setting by tire size. Individual plots of the percent slip versus
dynamometer horsepower setting by tire size and type are provided in
Appendix A.
The mean percent slip for each dynamometer horsepower setting and
nominal tire size is given in Table 1. The mean percent slip values for
the two lowest horsepower settings (5.9 and 6.8) differed significantly
from those for the three highest settings (7.4, 8.4 and 10.5).
B. Tire Size
As previously mentioned, tire size is highly correlated with dyna-
mometer horsepower setting due to the experimental technique used (i.e.,
applying a higher dynamometer load to larger tires). Therefore, to
determine if there is any effect due to tire size, there must be some
control on dynamometer horsepower setting to assure that the effect the
horsepower setting has on tire slip does not confound the results. The
method of analysis used to test for tire size effects was the Student's
t-test. The mean percent slip values for each tire size were compared
at each dynamometer horsepower setting. As can be seen from Table 1,
only a limited number of combinations could be tested due to the sample
size.
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1.60
1.20
.80
+ *
-5-
i^" TIRES
% SLIP
2.00 «•
0. *
5.50 7. BO '?.50
6.50 8.SO 10.SO
DYNAMOMFTEP HP SETTING
Figure 1
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-6-
Table 1
Average Percent Slip by Dynamometer Horsepower Setting
and Tire Size
Horsepower Nominal Tire Size
Setting 13 inch 14 inch 15 inch
5.9 1.00 0.46
n 16 8
6.8 1.34 _ _
n 8
7.4 1.51 0.58 _
n 98
8.4 0.82 1.08
n 8 18
10.5 0.91 1.17
n 1 12
n - Sample Size
The results of these analyses were that 13 inch tires differed
significantly from 14 inch tires at both the 5.9 and 7.4 horsepower
settings. At the 8.4 horsepower setting, 14 inch tires differed signi-
ficantly from 15 inch tires. It can be seen from Table 1 that 14 inch
tires slip less on the average than 13 and 15 inch tires, at each set-
ting, however, it can not be determined using this method of analysis
whether 13 or 15 inch tires have the larger percent slip since they were
not tested at the same horsepower settings. A comparison of the mean
percent slip values for 13 inch and 15 inch tires was conducted by
separating the data with respect to tire size and type for all dynamo-
meter horsepower settings. There were consistent results for each type:
13 inch tires had larger mean percent slip than 15 inch tires, however a
significant difference could only be detected for the case of bias ply
tires. It should be noted that these results are affected by the
dynamometer horsepower setting (i.e., slip increases with increasing
horsepower setting). Since the 15 inch tires had a higher horsepower
setting applied to them during testing than the 13 inch tires, one would
expect that the 15 inch tires would have the greater percent slip.
This, however, was not the case as can be seen from Table 2. It can
therefore be confidently concluded from the data set that 13 inch tires
slip more than 15 inch tires. For radial and bias belted tires, 14 inch
tires were significantly lower than the other two tire sizes. (Note,
due to the lack of data, conclusions may not be drawn with respect to 14
inch bias ply tires.)
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-7-
MEflN X SLIP VS
DTNflMOMETER HP SETTING
O
O
•
OJ
O
CO
O
C\J
CLJ
M
_J
CO
o
•
o
O
O
iir= 13 INCH TIRES
0= 14 INCH TIRES
D= 15 INCH TIRES
5.9 6.8 7.4 8.4 10.5
DTNflMOMETER HP SETTING
Figure 2
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-8-
MEflN
SLIP VS
TIRE TYPE
O
O
•
CVJ
O
C\J
CO
O
=f
•
O
O
O
*= 13 INCH TIRES
0= 14 INCH TIRES
D- 15 INCH TIRES
RflDIRL
BIflS BELTED
TIRE TYPE
BIflS PLY
Figure 3
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-9-
Table 2
Average Percent Slip by Tire Size
and Tire Type
Nominal Tire Size
Tire Type 13 inch 14 inch 15 inch
Radial 1.29 0.70 1.22
n 19 15 23
Bias Belted 1.13 0.52 0.83
n 4 10 3
Bias Ply 1.12 0.73
n 10 4
n = Sample size
Since there was not a random cross-section between tire size and
tire type in the sample, it is possible that the effect due to tire size
detected above may have been caused by tire type. Therefore, additional
analyses of variance were conducted on the percent slip with respect to
tire size for each horsepower setting and tire type. The results for 13
and 14 inch tires were consistent with the previous analyses: 14 inch
tires slip significantly less than 13 inch tires. However, the results
for the comparison between 14 and 15 inch tires by each tire type were
not consistent: for bias belted tires at 8.4 and 10.5 horsepower, signi-
ficant differences were not detected. In fact, at the 8.4 horsepower
setting, the mean percent slip for 15 inch tires was less than that for
14 inch tires. Examination of the data indicated that there was only
one. 15 inch bias belted tire tested at the 8.4 horsepower setting.
Therefore, the latter result was deemed inconclusive. For radial tires
at 8.4 horsepower, the results were that 15 inch tires have signifi-
cantly greater slip characteristics than 14 inch tires, which is con-
sistent with the previous analysis.
The physical cause of the above results is not known at this time.
However, it is suspected that the cause may be linked to the dynamometer
roll spacing and diameter. A roll spacing of 17.25 inches for the
standard twin roll dynamometer may not be the optimum for all tire
sizes. Some 'critical distance' from tire center to roll center may
exist at which tire slip is minimized. The distance obtained with the
use of 14 inch tires may be close to this 'critical distance1. The
magnitude of the tire slip may also be dependent upon the total hours-
of-operation logged on a particular dynamometer and the roll wear in-
curred. It has been observed that after many hours of use, the dyna-
mometer roll takes on an "hour glass" type shape. The width of this
"hour glassing" is a function of the track width of the variety of
vehicles operated on the dynamometer. The effects identified as being
due to tire size could be a result of a combination of both these
conditions.
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-10-
C. Tire Type
Analyses of variance were conducted for all the combined data and
also by tire size to determine if tire type has any effect on slip. For
the combined data, a significant difference due to tire type was detected.
A more detailed analysis indicated that this difference was due primarily
to a significantly lower slip for bias belted tires.
To assure that the difference detected above was caused by tire
type only, the same analysis was conducted by tire size. For 14 and 15
inch tires, this analysis detected a significant difference between the
tire type means. Again, more detailed analyses were done and 15 inch
bias belted and bias ply tires were found to have significantly less
percent slip than the 15 inch radial tires. Therefore, tire type
appears to have an effect on percent slip, regardless of tire size, with
radial tires slipping the most and bias ply tires slipping the least.
Table 2 shows the mean percent slip for each tire type at each tire size
and Figure 3 presents these means graphically.
D. Manufacturer
An analysis of variance of all the data indicated that there is a
significant effect due to tire manufacturer. A pairwise analysis iden-
tified Firestone tires as having a significantly lower mean percent slip
than either Goodyear or Goodrich tires. In addition, the mean percent
slip for Firestone tires was significantly less than the grand mean
value for all the manufacturers combined.
Since the tire type and size data were not randomly distributed
across all manufacturers, an analysis was conducted to test manufacturer
means taking these factors into account. This was to assure that any
effects found were not influenced by either tire type or size.
For radial tires, the analysis indicated that there was a signifi-
cant difference between the manufacturer means, however, for bias belted
and bias ply tires, no significant difference was found. The radial ply
tire data were further analyzed by tire size and it was found that
Firestone's 15 inch radial tires were the only significantly different
tires from the grand mean value for that category of tire. Table 3
shows the mean percent slip for each manufacturer by tire type and Table
4 presents the means by tire type and tire size.
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Table 3
Average Percent Slip by Manufacturer
and Tire Type
Manufacturer Radial Bias Belted Bias Ply
Goodyear
n
Goodrich
n
Uniroyal
n
Firestone
n
General
n
1.23
22
1.31
7
1.06
15
0.79
11
1.20
2
0.83
10
0.96
1
0.46
3
0.52
3
0.99
7
0.99
3
1.06
4
n = Sample Size
Table 4
Average Percent Slip by Manufacturer,
Tire Type and Tire Size
Radial Bias Belted Bias Ply
Manufacturer
Goodyear
n
Goodrich
n
Uniroyal
n
Firestone
n
General
n
13
1.36
12
—
1.31
4
1.01
3
—
14
0.75
3
—
0.77
6
0.62
6
—
15
1.21
7
1.31
7
1.21
5
0.98
2
1.20
2
13 14 15
1.13 0.57 0.76
442
0.96
1
0.46
3
0.52
3
— — —
13
—
1.33
3
0.99
3
1.06
4
—
15
—
0.74
4
—
—
—
n = Sample Size
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V. Conclusions
It is evident from these data that tires slip on the twin small-roll
dynamometer. This report has identified three major sources and one
minor source of tire slip, namely, dynamometer horsepower setting, tire
size, tire type and tire manufacturer, respectively. Although this
experiment was not designed to specifically study tire slip, it presents
data which may have an impact upon vehicle testing on the twin roll
Clayton dynamometer. Typically, tests conducted on EPA dynamometers
utilize the rear roll speed to represent vehicle speed and distance
travelled. The vehicle is loaded by a power absorber and inertia
assembly connected to the front roll. The amount of load the dynamo-
meter applies to the vehicle is based upon the velocity of the front
roll. The vehicle's actual road load horsepower at 50 mph is matched on
the dynamometer (less dynamometer residual friction) at 50 mph (front
roll speed). However, during the actual testing, the front roll may
never attain this velocity except if the test requires rear roll speeds
greater than 50 mph. As an example, if a vehicle equipped with radial
tires requiring a road load of 10 horsepower at 50 mph road speed was
operated at a steady state 50 mph rear roll speed on the Clayton dyna-
mometer, the load applied by the front roll could be as low as 9.66
horsepower. (Note: this example neglects any dynamometer frictional
forces associated with bearings and inertia weight aerodynamics.) This
estimate is based upon a mean steady state slip of 0.55 mph for radial
tires and the premise that the amount of power absorbed by the Clayton
dynamometer is proportional to the third power of the front roll speed.
The extent to which tire slip, as defined, occurs during a transient
test, such as the Federal Test Procedure, is not currently available.
VI. Recommendations
Based on the data presented in this report, it is recommended that
further testing be conducted to determine to what extent tire slip
occurs both on the road and on the twin small-roll dynamometer during
transient vehicle operation. If a definite problem is identified based
on that study, steps should be taken to correct the Federal Test Proce-
dure. It is suspected that the magnitude of the tire slip on the dyna-
mometer exceeds that on the road. It may be necessary to install a roll
coupling! device, in conjunction with some textured material on the front
roll, to reduce the slip and make the test speed more representative.
In addition, an in-house study of certification-vehicle tire types and
sizes should be conducted to determine possible trends toward tires
which slip more on the dynamometer. This study identifies 14 inch tires
as having low slip characteristics. A manufacturer may decide to over
or under specify the tires on his certification vehicle to avoid this
particular tire size.
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APPENDIX A
Percent Slip versus Dynamometer Horsepower Setting
-------
1.20 * *
?
+
?
.80 *
.40
-14-
13" PADIAL TIPFS
* SLIP
?.no *
+ -- — - + ---- + ----4-----»----.f-- —-*•-- —-•f----4'--.-- + -- —-4.
5.50 7.50 -1.50
*.5n 8.50 10.50
DYNAMOMETER HP SETTING
Plot A-l
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1.60
1.20
.80
.40
-15-
13" BIAS BELTED TIRES
% SLIP
2.00 *
0. *
5.50 7.50 Q.50
6.50 fl.<50 10.50
DYNAMQMRTEP HP SETTING
Plot A-2
-------
1.60
1.20
.80 * »
«
.40
-16-
13" BIAS PLY TIRES
% SLIP
2.00 *
0. *
5.50 7.50 0.50
6.50 8.50 10.50
DYNAMOMETER HP SETTING
Plot A-3
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1.60
1.20
-17-
IV RADIAL TIRFS
* SLIP
2.00 *
*
2
0. *
5.50 7.50 0.50
6.50 8.50 10.50
DYNAMOMETER HP SFTTING
Plot A-4
-------
1.60
1.20
-18-
14» BIAS BELTED TIRES
% SLIP
2.00 *
.80 +
2
.40
0. *
5.50 7.50 n.50
6.50 8.50 10.50
DYNAMOMETER HP SETTING
Plot A-5
-------
1.60
1.20
• RO
-19-
15" PADIAL TIRFS
% SLIP
2.00 *
5
3
0. *
5.50 7.50 Q.50
6.50 8.50 10.50
DYNAMOMETER HP SFTTING
Plot A-6
-------
1.60
.80
.40
-20-
15" BIAS BELTED TIRES
% SLIP
2.00 *
0. *
5.50 7.50 T.50
6.50 8.50 10.50
HP SETTING
Plot A-7
-------
1.60
1.20
.80
.40
-21-
15" BIAS PLY TIRES
% SLIP
?.oo *
5.50 7.50 c.50
6.50 8.50 10.50
DYNAMOMETER HP SETTING
Plot A-8
-------
1.60
1.20 + #
.RO
-22-
13" TIRES
% SLIP
2.00 *
0. *
5.50 7.50 '^.50
6.50 8.50 10.50
DYNAMOMETER HP SETTINC,
Plot A-9
-------
1.60
1.20
-23-
14" TIRES
% SLIP
2.00 *
.80 * *
2
2
.40 * *
0. *
5.50 7.50 0.50
6.50 8.50 10.50
DYNAMOMETER HP SETTING
Plot A-10
-------
1.60
.40
-24-
15" TIRES
% SLIP
?.00 *
l.?0 * ?
2
.RO *
•o
0. *
5.50 7.50 T.50
6.50 fl.50 10.50
OYNAMOMFTER HP SFTTING
Plot A-ll
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-25-
APPENDIX B
Tire Descriptions and Test Data
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-26-
Identification
Number
010
020
040
060
070
080
100
110
12B
13A
13B
15B
16A
16B
180
200
210
220
230
240
250
260
270
290
300
310
320
330
340
350
360
370
380
390
400
410
420
Manufacturer
Goodyear
Goodyear
Goodyear
Goodyear
Goodyear
Goodyear
Goodyear
Goodyear
B.F. Goodrich
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
Goodyear
Firestone
Uniroyal
Firestone
Uniroyal
B.F. Goodrich
B.F. Goodrich
Table B-l
Tire Descriptions
Size
BR70X13
BR78X13
HR78X14
H78X15
HR78X15
HR70X15
B78X13
H78X14
HR78X15
H78X15
H78X15
H78X15
HR70X15
HR70X15
GR78X15
HR78X15
GR78X15
GR78X15
GR78X15
LR78X15
ER78X14
FR78X14
FR78X14
HR78X15
ER78X14
ER78X14
E78X14
E78X14
E78X14
B78X13
BR78X13
BR78X13
BR78X13
B78X13
HR78X15
B78X13
GR78X15
Model/Type
Polyglass Radial WT
Polyglass Radial
Custom Polysteel Radial
Custom Power Cushion Polyglass
Polyglass Radial
Polyglass Radial WT
Cushion Belt Polyglass
Polyglass Cushion Bias Belted
Silvertown Steel Radial
Custom Long Mller
Custom Long Miler
Silvertown Belted
Silvertown Lifesaver XL-100
Silvertown Lifesaver XL-100
Steel Belted Radial
Custom Tread Steel Belted Radial
Steel Belted Radial PR6
Custom Tread Steel Belted Radial
Dual Steel II Radial
Steel Belted Radial PR6
Custom Tread Steel Belted Radial
Steel Belted Radial
Steel Belted Radial
Steel Belted Radial
Steel Belted Radial
Steel Belted Radial
Custom Power Cushion Polyglass
Fastrak Belted
Sup-R-Belted Deluxe Champion
Fastrak Belted
Steel Belted Radial
Steel Belted Radial
Steel Belted Radial
Deluxe Champion
Steel Belted Radial
Silvertown Bias Ply
Lifesaver 78 Steel Belted Radial
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-27-
Table B-2
Tire Mean Data
Nominal Delta
Tire Tire Size Roll Speed
Identification Hp Set (inches) (rev/sec)
010 5.9 13 10.09 1.26
010 5.9 13 7.47 0.95
010 6.8 13 12.11 1.56
010 7.4 13 14.48 1.79
020 5.9 13 7.40 0.95
020 6.8 13 12.90 1.62
020 7.4 13 12.42 1.58
020 5.9 13 9.96 1.28
040 10.5 15 9.94 1.32
060 10.5 15 7.10 0.88
060 8.4 15 4.94 0.64
070 8.4 15 8.26 1.09
080 10.5 15 9.24 1.20
080 8.4 15 9.74 1.22
100 5.9 13 6.41 0.79
100 5.9 13 7.25 0.92
100 6.8 13 11.47 1.38
100 7.4 13 11.34 1.41
110 10.5 14 7.14 0.91
12B 10.5 15 9.69 1.28
12B 8.4 15 8.02 1.05
13A 10.5 15 5.76 0.76
13A 8.4 15 5.42 0.69
13B 8.4 15 4.74 0.61
13B 10.5 15 6.71 0.86
15B 10.5 15 7.84 0.96
16A 8.4 15 15.05 1.86
16B 10.5 15 10.52 1.37
16B 8.4 15 9.33 1.15
180 8.4 15 7.49 0.97
200 10.5 15 9.35 1.23
200 8.4 15 8.19 1.02
210 8.4 15 7.98 1.07
220 8.4 15 10.94 1.44
230 10.5 15 10.30 1.35
230 8.4 15 7.86 1.04
240 10.5 15 11.02 1.42
240 8.4 15 9.56 1.21
250 5.9 14 3.92 0.56
250 8.4 14 6.39 0.92
250 7.4 14 5.48 0.76
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-28-
Table B-2 Continued
Tire
Identification
260
260
260
270
270
270
290
300
300
300
310
310
310
320
320
320
330
330
330
340
340
340
350
350
350
360
360
360
360
370
370
370
380
380
380
380
390
390
390
390
400
400
410
410
410
420
420
Hp Set
5.9
8.4
7.4
5.9
8.4
7.4
8.4
5.9
8.4
7.4
7.4
5.9
8.4
5.9
8.4
7.4
5.9
8.4
7.4
8.4
5.9
7.4
5.9
5.9
7.4
5.9
6.8
5.9
7.4
6.8
7.4
5.9
5.9
6.8
7.4
5.9
5.9
5.9
7.4
6.8
8.4
8.4
7.4
5.9
6.8
10.5
8.4
Nominal
Tire Size
(inches)
14
14
14
14
14
14
15
14
14
14
14
14
14
14
14
14
14
14
14
14
14
14
13
13
13
13
13
13
13
13
13
13
13
13
13
13
13
13
13
13
15
15
13
13
13
15
15
Delta
Roll Speed
(rev/sec)
4.65
8.77
5.67
3.49
6.69
3.11
7.38
3.66
6.13
5.15
4.27
3.28
5.58
2.73
4.28
3.07
2.02
5.38
3.16
4.71
2.81
3.73
6.27
6.74
10.34
10.07
11.38
8.20
12.48
5.59
11.51
6.74
8.24
10.19
11.70
10.90
8.15
6.03
9.82
9.70
9.42
8.29
12.75
7.38
11.58
10.13
8.40
Percent
Slip
0.64
1.11
0.79
0.48
0.89
0.43
0.98
0.52
0.87
0.71
0.61
0.48
0.80
0.36
0.59
0.42
0.28
0.68
0.43
0.66
0.38
0.52
0.79
0.85
1.33
1.22
1.44
1.05
1.58
0.73
1.47
0.84
1.05
1.33
1.51
1.35
1.00
0.76
1.25
1.23
1.24
1.09
1.63
0.92
1.45
1.37
1.12
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