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THETHETHETHE EFFECTSEFFECTSEFFECTSEFFECTS OFOFOFOF INFLATIONINFLATIONINFLATIONINFLATION GASGASGASGAS ONONONON TIRETIRETIRETIRE

LABORATORYLABORATORYLABORATORYLABORATORY TESTTESTTESTTEST PERFORMANCEPERFORMANCEPERFORMANCEPERFORMANCE

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JJJJOHN OHN OHN OHN HHHHARRISARRISARRISARRIS

TTTTRANSPORTATION RANSPORTATION RANSPORTATION RANSPORTATION RRRRESEARCH ESEARCH ESEARCH ESEARCH IIIINSTITUTENSTITUTENSTITUTENSTITUTE

EEEED D D D TTTTERRILLERRILLERRILLERRILL,,,, PPPPHHHH....D.D.D.D.

AAAAKRON KRON KRON KRON RRRRUBBER UBBER UBBER UBBER DDDDEVELOPMENT EVELOPMENT EVELOPMENT EVELOPMENT LLLLABORATORYABORATORYABORATORYABORATORY,,,, IIIINCNCNCNC....

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PPPPAPER APER APER APER 11118C8C8C8C----1111

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The

Effe

cts

of In

flatio

n G

as

on T

ire L

abor

ator

y T

est

Per

form

ance

Jam

es D

. Mac

Isaa

c Jr

., U

SD

OT

-N

HT

SA

Larr

y E

vans

& J

ohn

Har

ris, T

rans

port

atio

n R

esea

rch

Cen

ter,

Inc.

Ed

Ter

rill,

Ph.

D.,

Akr

on R

ubbe

r D

evel

opm

ent L

abor

ator

y, In

c.

Pre

sent

ed a

t IT

EC

200

8A

kron

, OH

Sep

tem

ber

17, 2

008

Nitr

ogen

Infla

tion

of

Pne

umat

ic T

ires

�In

flatio

n of

tire

s w

ith N

2ga

s is

pre

sum

ed to

be

bene

ficia

l. H

owev

er, t

here

are

a w

ide

varie

ty o

f cl

aim

s an

d co

unte

r-cl

aim

s:•

Bet

ter

infla

tion

pres

sure

ret

entio

n•

Low

er r

ollin

g re

sist

ance

•B

ette

r tr

eadw

ear

•Lo

wer

run

ning

tem

pera

ture

s•

Bet

ter

tire

dura

bilit

y•

Less

moi

stur

e•

Etc

.

Nat

iona

l Hig

hway

Tra

ffic

Saf

ety

Adm

inis

trat

ion

�N

HT

SA

Tra

ffic

Saf

ety

Fac

ts, 2

006*

•In

200

6, th

ere

wer

e an

est

imat

ed 5

,973

,000

pol

ice-

repo

rted

traf

fic c

rash

es, i

n w

hich

:–

42,6

42 p

eopl

e w

ere

kille

d–

2,57

5,00

0 pe

ople

wer

e in

jure

d–

4,18

9,00

0 cr

ashe

s in

volv

ed p

rope

rty

dam

age

only

•A

n av

erag

e of

117

peo

ple

died

eac

h da

y in

mot

or

vehi

cle

cras

hes

in 2

006

—on

e ev

ery

12 m

inut

es•

Mot

or v

ehic

le c

rash

es a

re th

e le

adin

g ca

use

of d

eath

for

ever

y ag

e fr

om a

ges

2 th

roug

h 34

•F

rom

199

4 to

200

4, N

HT

SA

est

imat

es th

at a

bout

400

fa

talit

ies,

ann

ually

(~

1% o

f tot

al m

otor

veh

icle

fata

litie

s),

may

be

attr

ibut

ed to

tire

failu

res

of a

ll ty

pes

*NH

TS

A T

raffi

c S

afet

y F

acts

, 200

6 D

ata,

DO

T H

S 8

10 8

09, N

HT

SA

’s N

atio

nal C

ente

r fo

r S

tatis

tics

and

Ana

lysi

s, U

pdat

ed M

arch

200

8

NH

TS

A T

estin

g of

Tire

s w

ith

Nitr

ogen

Infla

tion

�N

HT

SA

re-

dire

cted

tire

s fr

om o

ther

tire

pr

ogra

ms

to a

ddre

ss fo

ur b

asic

que

stio

ns:

•Is

ther

e a

syst

emat

ic a

nd q

uant

ifiab

le d

iffer

ence

in th

e in

flatio

n pr

essu

re lo

ss r

ate

(IP

LR)

of ti

res

whe

n in

flate

d w

ith g

ases

of v

aryi

ng n

itrog

en to

oxy

gen

ratio

s?•

Are

any

obs

erve

d di

ffere

nces

in IP

LR u

nifo

rm a

mon

g tir

es, o

r ar

e th

ey r

elat

ed to

var

iabl

es s

uch

as in

itial

in

flatio

n pr

essu

re, o

r tir

e de

sign

and

com

posi

tion?

•A

re th

ere

dire

ct e

ffect

s of

infla

tion

gas

com

posi

tion

on

the

rolli

ng r

esis

tanc

e of

tire

s?•

Are

ther

e di

ffere

nces

in ti

re d

urab

ility

per

form

ance

afte

r ac

cele

rate

d ag

ing

rela

ted

to th

e ni

trog

en-t

o-ox

ygen

ra

tio?

Tes

ting

�T

wen

ty-f

ive

pass

enge

r or

ligh

t tru

ck ti

re

mod

els

wer

e in

flate

d w

ith:

•S

hop

air

with

air

line

drye

r•

Dry

N2

gas

from

94

to 9

9% p

urity

–In

itial

pur

ge a

nd r

efill

use

d

•G

as c

ompo

sitio

n m

easu

red

at th

e be

ginn

ing

and

end

of te

st

�T

ires

wer

e te

sted

for:

•In

flatio

n pr

essu

re lo

ss r

ate

•La

bora

tory

rol

ling

resi

stan

ce•

Roa

dwhe

el e

ndur

ance

afte

r ov

en a

ging

•M

ater

ial p

rope

rtie

s

Tire

Infla

tion

Pre

ssur

e Lo

ss

�U

nder

-infla

ted

tires

are

a s

igni

fican

t pr

oble

m•

Acc

ordi

ng to

a N

HT

SA

stu

dy, 2

7% o

f pas

seng

er

cars

and

32%

of l

ight

truc

ks h

ave

at le

ast o

ne

tire

that

is s

ubst

antia

lly u

nder

infla

ted*

–“O

pera

ting

a ve

hicl

e w

ith s

ubst

antia

lly u

nder

-infla

ted

tires

can

res

ult i

n a

prem

atur

e tir

e fa

ilure

, suc

h as

in

stan

ces

of tr

ead

sepa

ratio

n an

d bl

owou

ts, w

ith th

e po

tent

ial f

or a

loss

of c

ontr

ol o

f the

veh

icle

. U

nder

-in

flate

d tir

es a

lso

shor

ten

tire

life

and

incr

ease

fuel

co

nsum

ptio

n.”

**

*Tir

e P

ress

ure

Spec

ial S

tudy

@ h

ttp:/

/ww

w.n

htsa

.dot

.gov

/peo

ple/

ncsa

/

**U

.S. T

rans

port

atio

n Se

cret

ary

Nor

man

Y. M

inet

a@

htt

p://

ww

w.d

ot.g

ov/a

ffai

rs/n

htsa

4601

.htm

Tire

Infla

tion

Pre

ssur

e Lo

ss

�T

ires

lose

infla

tion

gase

s co

ntin

uous

ly, s

ince

ru

bber

com

poun

ds a

re p

erm

eabl

e to

gas

m

olec

ules

and

loss

es e

xist

thro

ugh

tire/

whe

el/v

alve

inte

rfac

es�

Tub

eles

s tir

es r

equi

re a

n in

nerli

ner

com

poun

d w

ith lo

w p

erm

eabi

lity

to li

mit

the

loss

of

infla

tion

�T

he A

ST

M F

1112

-06

test

mea

sure

s th

e st

atic

lo

ss o

f inf

latio

n ga

s fr

om a

tire

ove

r tim

e•

Dat

a is

rep

orte

d as

% lo

ss /

mon

th

AS

TM

F11

12-0

6 In

flatio

n P

ress

ure

Loss

Rat

e (I

PLR

)�

Min

imum

sam

ple

of 2

tire

s pe

r m

odel

�C

lean

pai

nted

ste

el (

pref

erre

d) w

heel

or

othe

r m

ater

ial t

hat h

as b

een

leak

che

cked

�R

im s

ize

per

Tire

& R

im A

ssoc

iatio

n or

oth

er

stan

dard

s or

gani

zatio

n (p

refe

r m

easu

ring

rim)

�R

im s

eat d

iam

eter

mus

t be

with

in to

lera

nces

fr

om s

tand

ards

(co

nfirm

ed w

ith b

all t

ape)

�P

ress

ure

tran

sduc

er o

r ga

uge

�T

wo

met

al v

alve

s or

“T

”va

lve

+ m

etal

val

ve

AS

TM

F11

12-0

6 In

flatio

n P

ress

ure

Loss

Rat

e (I

PLR

)

�T

est R

oom

•M

ean

tem

pera

ture

s of

21,

24,

30

or 3

8°C

(n

orm

al te

st is

21°

C)

±0.6

°C (

±1°F

)•

For

cibl

y ci

rcul

ated

air

cont

rolle

d at

±3°

C (

±5°F

)

�G

auge

s or

Pre

ssur

e T

rans

duce

rs

•R

esol

utio

n 2

kPa

(0.2

5 ps

i) ac

cura

te to

±1%

of

mea

sure

d va

lue

(ope

ratin

g w

ithin

40

to 9

0% o

f fu

ll sc

ale)

�D

ata

Acq

uisi

tion

•R

ecor

d da

ta o

nce

per

day

for

180

days

or

com

pute

r da

ta a

cqui

sitio

n of

mor

e da

ta p

oint

s pe

r da

y fo

r a

shor

ter

dura

tion

test

�B

arom

eter

(H

igh

Acc

urac

y)

AS

TM

F11

12-0

6 In

flatio

n P

ress

ure

Loss

Rat

e (I

PLR

)

�T

ires

are

infla

ted

to a

spe

cifie

d pr

essu

re a

nd s

it st

atic

an

d un

load

ed in

a c

ontr

olle

d en

viro

nmen

t•

NH

TS

A te

stin

g us

ed F

MV

SS

No.

139

Hig

h S

peed

test

pre

ssur

es

•N

HT

SA

test

ing

was

con

duct

ed a

t 21º

C ±

3ºC

�T

he p

ress

ure

and

cond

ition

s ar

e m

onito

red

over

tim

e•

NH

TS

A te

stin

g us

ed 9

0 da

ys w

ith c

ontin

uous

mon

itorin

g of

the

pres

sure

via

com

pute

r in

terf

ace

–P

er th

e st

anda

rd th

e fir

st 3

0 da

ys d

ata

was

dis

card

ed

�D

ata

is th

en c

orre

cted

to a

sta

ndar

d te

mpe

ratu

re a

nd

baro

met

ric p

ress

ure

•21

ºC a

nd 1

01.3

kP

a

Exa

mpl

e D

ata

Out

put

30 -

90 d

ay d

ata

is u

sed

to c

alcu

late

In

flatio

n P

ress

ure

Loss

Rat

e (I

PLR

)

Rat

e st

abili

zes

afte

r in

itial

30

days

:0

to 1

5 da

y =

3.30

%/m

onth

y =

-0.0

011x

+ 5

.406

3R

2 =

0.9

788

0 to

30

day

= 3

.0 %

/mon

thy

= -0

.001

x +

5.4

053

R2

= 0.

991 30

to 9

0 da

y =

2.40

%/m

onth

y =

-0.0

008x

+ 5

.401

R2

= 0.

9989

60 to

90

day

=2.4

0%/m

onth

y =

-0.0

008x

+ 5

.400

2

R2 =

0.9

972

5.30

5.32

5.34

5.36

5.38

5.40

5.42

5.44

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

Day

s

LnP

Is th

ere

a di

ffere

nce

in (

IPLR

) w

hen

vary

ing

N2/

O2

ratio

?

�O

ne-w

ay A

NO

VA

ana

lysi

s of

IPLR

:

Infla

tion

Gas

and

Tire

Typ

e ar

e S

igni

fican

t Var

iabl

es

Dep

ende

nt V

aria

ble:

IPLR

, Rat

e @

90

Day

s, %

/mon

thS

um o

f

Sou

rce

DF

Squ

ares

M

ean

Squ

are

F V

alue

P

r >

F

R-S

quar

eM

odel

2

7

56.4

1

2

.089

22.5

6

<.

0001

0.9

02E

rror

66

6

.11

0.

092

Cor

rect

ed T

otal

93

62.

52

Sou

rce

DF

T

ype

III S

S

Mea

n S

quar

eF

Val

ue

Pr

> F

Infla

tion

Gas

1

6

.842

6

.842

73.9

0

<.

0001

Tes

t Lab

1

0

.017

0

.017

0.19

0.

6668

Tire

Typ

e

25

4

0.53

1

.621

17.5

1

<.

0001

IPLR

with

Air

vs. N

2 In

flatio

n

17 D

iffer

ent

Mod

els

of

Tire

s

Ave

rage

IP

LR fo

r N

2w

as 6

6% o

f A

ir

IPLR

, In

flatio

n w

ith A

ir o

r N

2 g

as

0

0.51

1.52

2.53

3.54

4.5

B1

B7

B8

B9

C7

C8

D6

G1

M1

M3

N2

O4

P3

S1

T2

U2

Y2

Tir

e T

yp

e

IPLR, 90-day

0%

10

%

20

%

30

%

40

%

50

%

60

%

70

%

80

%

90

%

10

0%

IPLR N2 / IPLR Air

Air

N2

%

Tire

Par

amet

ers

�A

ppro

xim

ate

inne

rline

r va

riatio

ns:

•P

olym

er:

100%

IIR

�80

/20

NR

/SB

R•

Car

bon

blac

k: 5

3 �

76 p

hr

•N

on-b

lack

fille

r: 0

�22

phr

•T

otal

fille

r: 6

7 �

105

phr

•V

olat

iles:

13 �

26 p

hr

•T

hick

ness

0.6

7 �

1.85

mm

�In

itial

Infla

tion

Pre

ssur

e: 2

20

� ���52

1 kP

a

IPLR

Ver

sus

Tire

C

onst

ruct

ion

�O

f the

var

iabl

es s

tudi

ed, i

nner

liner

com

posi

tion

and

min

imum

thic

knes

s ha

d m

ost s

igni

fican

t ef

fect

on

IPLR

•F

iller

and

vol

atile

s ha

d si

gnifi

cant

, but

less

er e

ffect

s

�A

naly

sis

of d

iffer

ence

in IP

LRbe

twee

n ai

r an

d N

2 (I

PLR

air

–IP

LRni

trog

en)

by ti

re ty

pe•

No

sign

ifica

nt e

ffect

of a

ny c

onst

ruct

ion

para

met

er•

No

sign

ifica

nt e

ffect

of i

nitia

l inf

latio

n pr

essu

re–

Pas

seng

er /

LT ti

res

Ben

efits

of N

itrog

en In

flatio

n on

IPLR

A

ppea

r to

be

App

licab

le to

All

Tire

Typ

es

Nitr

ogen

Infla

tion

& O

xyge

n C

once

ntra

tion

Equ

ipm

ent

Bal

ston

®72

-730

O

xyge

n A

naly

zer

Acc

urat

e to

<0

.1%

O2

O2

Mig

ratio

n D

urin

g T

est

Change in

Perc

ent

Oxy

gen C

once

ntr

atio

n D

uring

IP

L T

est

Vers

us

Sta

rtin

g O

xygen C

once

ntr

atio

n

y =

-0

.00

16x

2 - 0

.05

19x

+ 0

.216

6R

2 = 0

.91

56

-7-6-5-4-3-2-101

02

46

81

012

141

61

82

02

22

426

283

03

23

43

63

840

424

44

64

85

052

% In

itial O

2

%O2 Loss During Test (90 days)

Cha

nge

in O

2Le

vels

�F

aste

r m

igra

tion

of O

2ch

ange

s m

ixtu

re o

f ga

s du

ring

90-d

ay te

st•

Tire

s in

flate

d w

ith a

ir lo

stav

erag

e of

1.5

% O

2

•T

ires

infla

ted

with

N2

lost

or

gain

ed O

2to

ap

proa

ch e

quili

briu

m p

artia

l pre

ssur

e

�O

2le

vels

wer

e m

easu

red

for

76 ti

res

that

w

ere

in-s

ervi

ce (

19 v

ehic

les)

in A

kron

, OH

•T

ires

wer

e or

igin

ally

infla

ted

with

sho

p ai

r at

va

rious

loca

tions

, no

spec

ial p

roce

dure

s

O2

Con

tent

Ver

sus

Infla

tion

Pre

ssur

eIn

-Ser

vice

Tire

s

79111315171921

1015

2025

3035

40

Infla

tion

Pre

ssur

e, p

si

% O2No

Cor

rela

tion

Bet

wee

n In

flatio

n P

ress

ure

and

% O

2

Dur

ing

serv

ice

with

top-

offs

of

norm

al a

ir, th

e ox

ygen

pe

rmea

tes

out

at a

fast

er r

ate

than

the

nitr

ogen

.

Thi

s ca

n re

sult

in a

>50

%

redu

ctio

n in

ne

t oxy

gen

leve

ls in

the

tire

infla

tion

gas

durin

g no

rmal

ser

vice

.

O2

Leve

l Sig

nific

antly

R

educ

ed In

-Ser

vice

Oxy

gen

Ran

ge

(% o

f in

flat

ion

gas)

N

umbe

r of

Tir

es

9 � ���

11

4 11

.1 � ���

13

18

13.1

� ��� 1

5 18

15

.1 � ���

17

17

17.1

� ��� 1

9 14

19

.1 � ���

20.

0 5

15.0

2 A

vera

ge

2.79

S

tan

dard

Dev

iati

on

Indi

cate

s R

educ

ed P

oten

tial B

enef

its

for

N2

Infla

tion

in N

orm

al T

ire S

ervi

ce

IPLR

Adv

anta

ge fo

r N

2In

Ser

vice

The

oret

ical

Dis

trib

utio

n of

IP

LR

Nor

mal

ized

to

Air

Rat

e =

100

for

Tir

e T

ype.

Nor

mal

ized

Dis

trib

utio

n of

:__

___

Air

wit

h 20

.9%

O2

____

_--

----

----

----

Nit

roge

n -

----

----

----

--__

-A

ir, D

eple

ted

of O

2 in

Ser

vice

__-

IPL

Rav

g=2.

1

IPL

Rav

g=1.

4IP

LR

avg=

1.8

Dyn

amic

Infla

tion

Pre

ssur

e Lo

ss –

Roa

dwhe

el T

estin

g

Infla

tion

Pre

ssur

e Lo

ss D

urin

g R

oadw

heel

T

estin

g W

as 3

7% L

ess

for

Tire

s In

flate

d w

ith N

2vs

. Tire

s In

flate

d w

ith A

ir

Cha

nge

in %

O2

Dur

ing

Dyn

amic

Loa

ded

Ope

ratio

n

Hig

her

%O

2G

as D

iffus

es M

ore

Rap

idly

D

urin

g D

ynam

ic R

oadw

heel

Tes

ting

Doe

s N

2H

ave

a D

irect

Effe

ct

on R

ollin

g R

esis

tanc

e?

�24

Tire

s w

ere

com

pare

d fo

r R

ollin

g R

esis

tanc

e, e

ither

in

flate

d w

ith N

2 or

Air

•S

AE

J12

69 S

ingl

e-P

oint

Tes

t�

Ave

rage

Rol

ling

Res

ista

nce

•A

ir =

12.

80 p

ound

s ±0

.38

•N

2=

12.

65 p

ound

s ±0

.44

�N

o D

irect

Effe

ct O

bser

ved

for

N2

Infla

tion

on T

ire

Rol

ling

Res

ista

nce

�T

he O

nly

Sig

nific

ant E

ffect

on

Tire

Rol

ling

Res

ista

nce

may

be

Indi

rect

: •

Due

to B

ette

r R

eten

tion

of In

flatio

n P

ress

ure

over

Tim

e

Effe

cts

on T

ire D

urab

ility

�T

he b

enef

its o

f N2

infla

tion

on o

ven-

aged

tir

es h

as b

een

show

n*

�T

he ti

res

wer

e fil

led

with

50

/50

N2/

O2,

air

or N

2an

d ov

en-a

ged

for

5 w

eeks

@

65ºC

�T

hey

wer

e th

en te

sted

ac

cord

ing

to th

e F

MV

SS

13

9 E

ndur

ance

and

Low

P

ress

ure

Tes

t (to

failu

re

or 3

5.5

hour

s st

op-f

inis

h)

�50

/50

N2/

O2

had

a si

gnifi

cant

del

eter

ious

ef

fect

. T

ires

aged

with

N2

or a

ir in

flatio

n al

l pas

sed

test

@ 3

5.5

hrs

*N

. Tok

ita, W

.D. S

igw

orth

, G.H

. Nyb

akka

n, G

.B. O

uyan

g, “

Long

-Ter

m D

urab

ility

of T

ires,

”P

aper

18

D17

, Pro

ceed

ings

of t

he In

tern

atio

nal R

ubbe

r C

onfe

renc

e, K

yoto

, 198

5, p

. 672

-679

.

J. M

. Bal

dwin

, D.R

. Bau

er, a

nd K

.R. E

llwoo

d, “

Effe

cts

of N

itrog

en In

flatio

n on

Tire

Agi

ng a

nd

Per

form

ance

,”P

aper

2, p

rese

nted

at R

ubbe

r D

ivis

ion,

AC

S, G

rand

Rap

ids,

MI,

May

17-

19, 2

004.

U. K

arm

akar

, “E

ffect

of N

itrog

en P

urity

on

the

Oxi

datio

n of

Bel

t Coa

t Com

poun

d,”

pres

ente

d at

th

e In

tern

atio

nal T

ire E

xpos

ition

and

Con

fere

nce,

Akr

on, O

H, S

epte

mbe

r, 2

006.

Con

clus

ion

(I)

�In

labo

rato

ry te

stin

g, ti

res

infla

ted

with

94-

99%

N

2sh

owed

a 3

4% r

educ

tion

in p

ress

ure

loss

ve

rsus

tire

s in

flate

d w

ith a

ir (7

8% N

2)•

Bas

ed o

n re

duce

d O

2ob

serv

ed fo

r in

-ser

vice

tire

s, th

e be

nefit

s of

N2

in s

ervi

ce w

ould

be

sign

ifica

ntly

red

uced

•T

ires

infla

ted

with

N2

abov

e 97

% p

urity

sho

wed

di

ffusi

on o

f O2

into

the

tire

at 9

0 da

ys�

Sim

ilar

redu

ctio

n in

IPLR

for

tires

infla

ted

with

N

2du

ring

800-

hour

dyn

amic

, loa

ded

road

whe

el

test

�In

nerli

ner

com

posi

tion

and

initi

al in

flatio

n pr

essu

re h

ad n

o si

gnifi

cant

effe

ct o

n re

duct

ion

of IP

LR fo

r N

2ve

rsus

air

Con

clus

ions

(I

I)

�T

ire in

flatio

n w

ith N

2ve

rsus

air

had

no

sign

ifica

nt e

ffect

on

rolli

ng r

esis

tanc

e•

Ben

efits

of N

2w

ill li

kely

be

indi

rect

from

impr

oved

re

tent

ion

of in

flatio

n pr

essu

re o

ver

time

�La

bora

tory

tire

end

uran

ce a

fter

oven

agi

ng w

as

redu

ced

by h

igh

O2

cont

ent i

n in

flatio

n ga

s du

ring

oven

agi

ng

•T

ires

infla

ted

with

air

or N

2du

ring

agin

g co

mpl

eted

the

post

-ove

n 35

.5 h

our

test

with

no

failu

res

•P

revi

ous

stud

ies

have

sho

wn

bene

fits

for

tire

road

whe

el

endu

ranc

e w

hen

tires

infla

ted

with

N2

durin

g ag

ing