TTTTHE HE HE HE IIIINTERNATIONAL NTERNATIONAL NTERNATIONAL NTERNATIONAL TTTTIRE IRE IRE IRE EEEEXHIBITION XHIBITION XHIBITION XHIBITION &&&& CCCCONFERENCEONFERENCEONFERENCEONFERENCE

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FROMFROMFROMFROM DIFFERENTDIFFERENTDIFFERENTDIFFERENT TESTTESTTESTTEST METHODSMETHODSMETHODSMETHODS ANDANDANDAND ININININ

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Rol

ling

Res

ista

nce

of T

ires

for

Ligh

t V

ehic

les,

II:

Com

paris

on o

f Rol

ling

Res

ista

nce

Val

ues

Obt

aine

d fr

om D

iffer

ent T

est

Met

hods

and

in D

iffer

ent L

abor

ator

ies

Larr

y E

vans

& J

ohn

Har

ris, T

rans

port

atio

n R

esea

rch

Cen

ter,

Inc.

Jam

es D

. Mac

Isaa

c Jr

., U

SD

OT

-N

HT

SA

Pre

sent

ed a

t IT

EC

200

8A

kron

, OH

Sep

tem

ber

17, 2

008

Obj

ectiv

e

�S

elec

t a M

etho

d to

Mea

sure

Tire

Rol

ling

Res

ista

nce

in O

rder

to C

ompa

re T

ires

•S

AE

J24

52 v

alue

s at

var

ious

spe

ed, l

oad,

and

in

flatio

ns u

sed

to r

elat

e tir

e pr

oper

ties

to v

ehic

le–

SM

ER

F (

Sta

ndar

d M

ean

Equ

ival

ent R

ollin

g F

orce

)

•S

AE

J12

69 a

nd IS

O 1

8164

des

crib

e th

e tir

e re

spon

se a

t var

ious

load

and

infla

tion

cond

ition

s–

SR

C (

Sta

ndar

d R

efer

ence

Con

ditio

n)

•S

AE

J12

69 a

nd IS

O 2

8580

test

a ti

re a

t st

anda

rd c

ondi

tions

of s

peed

, loa

d, a

nd in

flatio

n

Mea

surin

g R

ollin

g R

esis

tanc

e

�E

valu

ate

Sou

rces

of V

aria

bilit

y in

Tes

ting

•T

ire –D

iffer

ent T

ire T

ypes

–D

iffer

ent T

ires

of S

ame

Typ

e–

Sam

e T

ire –

Rep

eat T

estin

g

•La

b•

Tes

t

Tes

t Mat

rix

�F

ive

Tes

t Pro

toco

ls�

25 T

ire T

ypes

�2

Labs

�C

appe

d or

Reg

ulat

ed P

ress

ure

(J12

69)

�F

irst,

Sec

ond

and

Thi

rd T

ests

on

Indi

vidu

al

Tire

s�

Diff

eren

t Inf

latio

n G

as�

641

Tes

ts�

Onl

y on

e tir

e w

as a

n ou

tlier

from

oth

er ti

res

of

the

sam

e m

odel

AN

OV

A

�A

naly

sis

of V

aria

nce

was

con

duct

ed o

n re

sults

fr

om e

ach

test

•S

AE

J12

69 S

ingl

e-P

oint

•S

AE

J12

69 M

ulti-

Poi

nt

–C

alcu

late

d va

lue

at S

RC

usi

ng r

egre

ssio

n sp

ecifi

ed

•IS

O D

IS28

580

Sin

gle-

Poi

nt•

ISO

181

64 M

ulti-

Poi

nt–

Cal

cula

ted

at S

RC

usi

ng J

1269

reg

ress

ion

met

hod

•S

AE

J24

52–

SM

ER

F–

Cal

cula

ted

valu

e at

SR

C u

sing

J24

52 r

egre

ssio

n

SA

E J

1269

Sin

gle-

Poi

nt

Dep

ende

nt V

aria

ble:

Rol

ling

Res

ista

nce

Sum

of

Mea

nS

ourc

e

DF

S

quar

es

S

quar

e

F V

alue

P

r >

FM

odel

29

49

358.

7

170

2.0

15

122.

2<.

0001

Err

or

19

1

2

1.5

0.11

Unc

orre

cted

Tot

al

22

0

49

380.

2

R-S

quar

e

Coe

ffV

arR

oot M

SE

RR

Mea

n0.

9959

852.

3715

65

0.

3354

87

1

4.14

623

Sou

rce

D

F

Typ

e III

SS

Mea

n S

quar

e

F V

alue

P

r >

FLa

b W

here

Tes

ted

1

9

.45

9.

4583

.99

<.

0001

Pro

cedu

re fo

r In

flatio

n

1

2.99

2.

9926

.62

<.

0001

Tes

t Ord

er

2

0

.07

0.

036

0.

32

0.7

265

Typ

e (T

ire M

odel

)

24

4

871.

64

20

2.9

8

180

3.49

<

.000

1

AN

OV

A C

ompa

rison

1,69

9.70

89.9

485

3.61

4,57

4.38

1,80

3.49

F V

alue

–T

ire M

odel

26.5

74.

30*

0.68

0.23

0.32

F V

alue

–T

est O

rder

NA

NA

NA

NA

26.6

2F

Val

ue -

Cap

ped

/ R

egul

ated

544.

344.

30*

2.14

11.2

483

.99

F V

alue

-La

b

0.99

530.

9891

0.99

670.

9960

0.99

60R

2

23,5

352,

687.

68,

320.

915

,929

.515

,122

.2F

Val

ue

J245

2 S

ME

RF

ISO

181

64(1

0 T

ires)

ISO

D

IS28

580

J126

9 M

ulti-

Poi

ntJ1

269

Sin

gle-

Poi

nt

Tes

t

* V

aria

ble

s w

ere c

on

fou

nd

ed

AN

OV

A C

oncl

usio

ns

�F

and

R2

valu

es in

dica

te th

at th

e so

urce

s of

var

iatio

n ar

e ac

coun

ted

for

in m

odel

•T

ire ty

pe is

the

mos

t sig

nific

ant v

aria

ble

•T

he tw

o la

bs s

tudi

ed p

rodu

ced

sign

ifica

ntly

di

ffere

nt v

alue

s•

Cap

ped

vs. r

egul

ated

infla

tion

pres

sure

dur

ing

the

test

was

sig

nific

ant

•F

irst,

seco

nd, o

r th

ird te

st o

n th

e sa

me

tire

was

no

t a s

igni

fican

t var

iabl

e

Lab

Var

iatio

n

�T

est o

rder

(1

st, 2

nd, 3

rd)

igno

red

�C

oeffi

cien

t of V

aria

tion

with

in a

lab

for

a tir

e ty

pe o

n a

test

was

≤

2.5%

•V

alue

s w

ere

norm

ally

dis

trib

uted

with

in e

ach

lab

�T

here

was

a s

igni

fican

t var

iatio

n be

twee

n la

bs fo

r al

l tes

ts

Lab

Offs

et

J126

9 S

ingl

e-P

oint

Tes

t

Rol

ling

Res

ista

nce

@ L

ab B

= 0

.257

+ 1

.024

*(L

ab A

)

Lab

Offs

et

0.99

15B

= -

0.14

3 +

1.07

7*A

J245

2S

ME

RF

0.96

23B

= 0

.714

+ 0

.908

*AIS

O 1

8164

0.96

23B

= -

0.09

9 +

1.01

2*A

ISO

285

80

Sin

gle-

Poi

nt

0.96

59B

= -

1.74

6 +

1.01

2*A

J126

9 M

ulti-

Poi

nt

0.99

75B

= 0

.257

+1.0

24*A

J126

9 S

ingl

e-P

oint

R2

Cor

rela

tion

of L

ab B

to L

ab A

Tes

t

Lab

to L

ab C

orre

latio

n

�S

tatis

tical

ly s

igni

fican

t offs

et b

etw

een

labs

.•

Lab

B h

ad h

ighe

r va

lues

than

Lab

A fo

r 3

of th

e te

sts

•La

b B

had

low

er v

alue

s th

an L

ab A

for

1 te

st

•E

qual

on

aver

age

for

1 te

st

�A

slig

htly

bet

ter

pred

ictio

n of

lab

offs

et

coul

d be

obt

aine

d w

ith a

non

-line

ar

equa

tion,

esp

ecia

lly fo

r m

ulti-

poin

t tes

ts

Lab-

to-L

ab O

ffset

Cor

rela

tion

of

Lab

B t

o L

ab A

fo

r al

l con

diti

ons

of t

he J

1269

M

ulti

-Poi

nt t

est.

T

est

Poi

nt 1

[C

ap

ped

In

flatio

n]is

sig

nifi

cant

ly

offs

et

Var

iabi

lity

of T

est

1.9%

J245

2 S

ME

RF

5.2%

ISO

181

64 (

10 T

ires)

2.2%

ISO

DIS

2858

0

2.4%

J126

9 M

ulti-

Poi

nt

2.4%

J126

9 S

ingl

e-P

oint

Coe

ffici

ent o

f Var

iatio

nT

est

Mea

surin

g R

ollin

g R

esis

tanc

e

�S

ourc

es o

f Var

iabi

lity

in T

estin

g•

Diff

eren

t Tire

s of

Sam

e T

ype

–O

nly

1 T

ire s

igni

fican

tly d

iffer

ent

•S

ame

Tire

–R

epea

t Tes

ting

–N

o si

gnifi

cant

effe

ct

•La

b–

Sig

nific

ant d

iffer

ence

s�

Var

ies

by te

st a

nd c

ondi

tions

•T

est

–A

ll te

sts

have

low

Coe

ffici

ent o

f Var

iatio

n (C

.V.)

Ran

king

Tire

Rol

ling

Res

ista

nce

�D

ata

for

valu

es fr

om L

ab A

cor

rect

ed to

La

b B

val

ues

usin

g co

rrel

atio

n eq

uatio

ns�

Do

test

s ra

nk-o

rder

tire

s di

ffere

ntly

?�

Rol

ling

resi

stan

ce o

f tire

s w

as g

roup

ed

usin

g le

ast s

igni

fican

t diff

eren

ces

at 9

5%

conf

iden

ce le

vel f

or d

ata

from

eac

h te

st

Cor

rela

tion

of T

est D

ata

5T =

SA

E J

2452

SM

ER

F

valu

e, L

ight

Tru

ck T

ires

5P

= S

AE

J2

452

SM

ER

F

valu

e, P

asse

nger

Tire

s

4T =

SA

E J

2452

val

ue @

S

RC

, Lig

ht T

ruck

Tire

s

4P =

SA

E J

2452

val

ue @

S

RC

, Pas

seng

er T

ires

3 =

ISO

18

164

valu

e @

S

RC

2 =

SA

E J

1269

mul

ti-po

int

valu

e @

SR

C

1 =

ISO

285

80 s

ingl

e-po

int v

alue

Pas

seng

er T

ire G

roup

s

R4

B12

B13

R4

B12

B13

B13

B12

R4

B13

B12

B12 R4

B13

R4

B13

B12

4(H

ighest

)

D10 U3

B14 P5

B15

D10 U3

B14 P5

B15

U3

B14

D10

B14 U3

B15 P5

U3

D10 P5

B14

B15

D10 U3

P5

B14

B15

3

G9

M13

G10

M14

B10

G9

M13

G10

M14

B10

G9

M14

G10

G9

M13

M14

G10

B10

G9

G10

M14

M13

B10

G9

G10

M13

M14

B10

2

G11 G8

B11

G11

B11 G8

G11 G8

B11

G8

B11

G11

G11

B11 G8

B11 G8

G11

1 (L

ow

est

)

J245

2,

SME

RF

J245

2 @

SR

CIS

O 1

8164

ISO

285

80J1

269

mul

ti-

poin

t@

SRC

J126

9 Si

ngle

-P

oint

Gro

up

Ligh

t Tru

ck T

ire G

roup

s

C9

C9

C9

C9

C9

6(H

ighest

)

D9

D9

D9

D9

D9

5

M12

M10

M11

K4

P4

D8

D7

M12

M10

M11

K4

P4

D8

D7

M10

M

12

M11

K4

P4

D8

D7

M10

M12

K4

M11

D8

P4

D7

M10

M12

M11

D8

K4

D7

P4

4 (L

ow

est

)

J245

2, S

ME

RF

J245

2 @

SR

CIS

O 2

8580

J126

9 m

ulti

-po

int@

SR

CJ1

269

Sing

le-

Poi

nt

Gro

up

Sel

ectio

n of

Met

hod

�A

ll m

etho

ds p

rodu

ce d

ata

with

low

var

iatio

n�

All

met

hods

ran

k tir

es in

to th

e sa

me

grou

ps�

Dat

a fr

om a

ny m

etho

d ca

n be

cor

rela

ted

to d

ata

from

any

oth

er m

etho

d�

Sin

gle-

poin

t met

hod

is m

ost e

ffici

ent

�A

ny m

etho

d se

lect

ed w

ill n

eed

a pr

oced

ure

to

acco

unt f

or la

b-to

-lab

diffe

renc

es

Ran

king

Tire

s U

sing

RR

C

�R

ollin

g R

esis

tanc

e C

oeffi

cien

t (R

RC

) is

of

ten

used

to r

epor

t the

rol

ling

resi

stan

ce

of ti

res

•R

RC

is R

ollin

g R

esis

tanc

e F

orce

/ N

orm

al F

orce

–U

sing

sam

e un

its r

emov

es th

e di

men

sion

�W

hen

com

parin

g tir

es te

sted

at t

he s

ame

load

, the

re is

no

chan

ge in

com

paris

ons

�C

an R

RC

be

used

to c

ompa

re ti

res

of

diffe

rent

load

rat

ings

?

Cor

rela

tion

of T

est D

ata

5T =

SA

E J

2452

SM

ER

F

valu

e, L

ight

Tru

ck T

ires

5P

= S

AE

J2

452

SM

ER

F

valu

e, P

asse

nger

Tire

s

4T =

SA

E J

2452

val

ue @

S

RC

, Lig

ht T

ruck

Tire

s

4P =

SA

E J

2452

val

ue @

S

RC

, Pas

seng

er T

ires

3 =

ISO

18

164

valu

e @

S

RC

2 =

SA

E J

1269

mul

ti-po

int

valu

e @

SR

C

1 =

ISO

285

80 s

ingl

e-po

int v

alue

RR

C C

alcu

latio

n

�W

hile

RR

C is

dim

ensi

onle

ss, i

t is

not

inde

pend

ent o

f con

ditio

ns o

f tes

ting

�F

or p

asse

nger

tire

s us

ing

J126

9 R

R:

RR

_For

ce=

Loa

d*(A

1+

A2*

Load

+ A

3÷P

ress

ure)

–D

ivid

ing

both

sid

es b

y lo

ad

RR

C =

A1

+ A

2*Lo

ad +

A3÷

Pre

ssur

e–

At c

onst

ant p

ress

ure

RR

C =

A2*

Load

+ A

1 +

A3÷

k

RR

C is

stil

l a fu

nctio

n of

load

J245

2 an

d LT

tire

s ar

e ev

en m

ore

com

plex

RR

C V

s. L

oad

–T

ire T

ype

D7

RR

C: T

ire D

7 (L

T)

0.00

8

0.00

9

0.01

0.01

1

0.01

2

0.01

3

0.01

4

0.01

5

0.01

6

0.01

7 1000

1500

2000

2500

3000

Load

, Pou

nds

RR Index, [Mich LTX=100]

Ran

ge o

f Ave

rage

Val

ues

for A

ll Tire

s

RR

C is

be

twee

n 0.

0093

and

0.

0161

, de

pend

ing

on

test

con

diti

on.

It is

not

an

intr

insi

c pr

oper

ty o

f th

e ti

re

Con

clus

ions

(I)

�U

p to

3 r

epea

t tes

ts o

f the

sam

e tir

e ha

s no

si

gnifi

cant

effe

ct o

n ro

lling

res

ista

nce

valu

es�

As

expe

cted

, tes

ting

with

cap

ped

infla

tion

pres

sure

pro

duce

s a

low

er v

alue

, due

to

incr

ease

d pr

essu

re�

Tire

s of

the

sam

e m

odel

and

siz

e pr

oduc

e eq

uiva

lent

rol

ling

resi

stan

ce v

alue

s, ±

~6%

•D

ata

is n

orm

ally

dis

trib

uted

•

1 ou

tlier

tire

dis

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