Page 368 of 396
Maximum
tireload :isthe maximum
permitted weightforwhich thetire is
approved.
Further information ontire loads
(Y page 367). Uniform
TireQuality Grading
Stand ards Overview
ofTire Quality Grading
Stand ards The
Uniform TireQuality Grading isaU.S.
Government requirement. Theirpurpose isto
provide driverswithconsist entand reliabl e
information regardingtireperformance. Tire
manufacturers arerequired tograde tires
using threeperformance factors:tread
wear :,tire tract ion;, and temperature
resistance =.Although notaGover nment of
Canada requirement,all tires made forsale in
Nort hAm eric ahave thesegrades brandedon
the sidewall. i
The
actual values fortires are vehic le-
spec ificand may deviat efro mt hevalues in
the illustration .
Where applicable, thetire grading
information canbefound onthe tire sidewa ll
between thetread shoulder andmaximum
tire width.
For example: Tread
wear Tra
ction Temp
erature 200 AA A All
passenger cartires must confor mto the
statutory safetyrequirements inaddition to
these grades. Tread
wear
The tread weargrade isac omparative rating
based onthe wear rateofthe tire when tested
under controlled conditionsonaspecified
U.S. governm entcourse. Forexample, atire
graded 150would wearoneandone-half
times aswell onthe governm entcourse asa
tire graded 100.
The relative performanc eof tires depends
upon theactual conditionsoftheir use,
however, andmay depart significant lyfrom
the norm, duetovariations indriving habits,
service practices anddifferenc esinroad
charact eristics andclimate conditions. Tr
action G
WARNIN
G The
tract iongrade assigned tothis tireis
based onstraight- aheadbraking traction
test s,and does notinclude acceleration,
corn ering, hydroplaning, orpeak traction
character istics.
The tract iongrades, fromhighest tolowest,
are AA, A,B,and C.Those grades represent
the tire's ability tostop onawet surface as
measured undercontrolled conditionson
specified governmenttest surfaces ofasphalt
and conc rete. Atire mark edCmay have poor
tr act ion perf ormance. G
WARN
ING If
ice has formed onthe road, tiretract ion will
be subst antially reduc ed.Und ersuch weathe r
con ditio ns,drive ,ste erand brak ewith
ext reme caution.
The safe speed onawet, snowcov ered oricy
road isalways lowerthanondry road
surf aces. 366
Unifor
mTir eQua lityGrad ing Stand ardsWheels and tires
Page 370 of 396
Tire
size des ignati on,load -bea ring
cap acit yand speed ratin g :
Tire width
; Nom inalaspec tratio in%
= Tire code
? Rim diame ter
A Load bearingindex
B Spe edrating i
Tire
datais veh icle-spec ificand may
devi atefrom thedat ain theex ample .
Gener al:depen dingon theman ufacturer's
st and ards ,th esiz eimpr inted inthetir ewall
may notco ntain any letters or may contain
on elet tert hat precedes thesize description.
If there isno letter preceding thesize
description (asshown above): theseare
passenger vehicletiresaccording to
European manufacturing standards.
If "P" precedes thesize description: theseare
passenger vehicletiresaccording toU.S.
manufacturing standards.
If "LT" precedes thesize description: these
are light truck tiresaccording toU.S.
manufacturing standards.
If "T" precedes thesize description: theseare
compact emergency sparewheels athigh tire
pressure, tobe used onlytemporarily inan
emergency.
Tire width: tirewidth :shows thenominal
tire width inmillimeters.
Nominal aspectratio: aspect ratio;isthe
size ratio between thetire height andthetire
width andisshown inpercent .The aspect ratio
iscalculated bydividing thetire width by
the tire height.
Tire code: tirecode =specifies thetire type.
"R" represents radialtires."D"represents
diagonal tires,"B"represents diagonalradial
tires.
Optionally, tireswithamaximum speedof
over 149mph(240 km/h)mayhave "ZR"in
the size description dependingonthe
manufacturer (e.g.245/ 40ZR18).
Rim diamet er:rim diameter ?isthe
diameter ofthe bead seat,notthediameter
of the rim flange. Therimdiameter is
specified ininches (in).
Load bearing index:loadbearing indexA
is anumerical codewhich specifies the
maximum load-bearing capacityofatire. G
WARNING The
tireload rating mustalwaysbe atleast
half ofthe GAWR ofyour vehicle. Otherwise,
sudden tirefailure maybethe result which
could cause anaccident and/orserious injury
to you orothers.
Always replace rimsandtires withrims and
tires having thesame specifications
(designation, manufacturer andtype) as
shown onthe original part. G
WARNING Do
not overload thetires byexceeding the
specified loadlimit asindicated onthe Tire
and Loading Informationplacard onthe
driver's doorB-pillar. Overloading thetires
can overheat them,possibly causinga
blowou t.Overloading thetires canalso result
in handling orsteering problems, orbrake
failure.
Example:
The load bearing index91isequiva lenttoa
maximum loadof1356 lbs(615 kg)that the
tire can carry. Forfurther information onthe
maximum tireload inkilograms andpounds,
see (Ypage 365). 368
Tire
labeli ngWheels and tires
Page 375 of 396
Maximum
loadrating
The maximu mload rating inkilograms or
pounds isthe maximum weightforwhich a
tire isapproved. Maximu
mperm issible tirepressur e
Maximum permissible tirepressure forone
tire. Maximu
mload onone tire
Maximum loadonone tire. This iscalculated
by dividing themaximum axleload ofone axle
by two. PSI
(pounds persquar einch)
As tand arduni tofm easure fortire pressure. Aspect
ratio
Relationship betweentireheight andtire
width inpercen t. Tir
epr essure
This ispressure insidethetire applying an
outward forceto each square inchofthe tire's
surface. Thetirepressure isspecified in
pounds persquare inch(psi), inkilopascal
(kPa) orinbar. Thetirepressure shouldonly
be corr ectedwhen thetires arecold. Tir
epr essure ofcold tires
The tires arecold:
R ifthe vehicle hasbeen parked without
direct sunlight onthe tires foratleast three
hours and
R ifthe vehicle hasnotbeen driven morethan
1 mile (1.6km). Tr
ead
The part ofthe tire that comes intocon tact
with theroad. Bead
The tirebead ensures thatthetire sits
securely onthe wheel. Thereareseveral steel
wires inthe bead topreven tthe tire from
comin gloose fromthewheel rim. Sidewall
The part ofthe tire between thetread andthe
bead. Weight
ofoptional extras
The combin edweight ofthose option alext ras
that weigh morethanthereplaced standard
part andmore than2.3kilograms (5lbs).
These optionalext ras, such ashigh-
perform ancebrakes, levelcontrol, aroof rack
or ahigh-perf ormancebatter y,are not
included inthe curb weight andaccesso ry
weight. TIN
(Tire Identificat ionNum ber)
This isaunique identifierwhich canbeused
by atire manufact urertoident ifytires, for
example foraproduct recall,andthus ident ify
the purchasers. TheTINismade upofthe
manufact urer'sidentitycode, tiresize, tire
type code andthemanufact uringdate. Load
bearing index
The load bearing index(alsoloadindex) isa
code thatcontains themaximum loadbearing
capacity ofatire. Definition
ofter ms fortires and loading
373Wheels and tires Z