Tire Replacement; Tread Wear - BMW 325Ci Owner's Manual

Tire replacement

T o m aintain g o o d h a n dlin g a n d v e hicle
re s p o n s e , u s e o nly tire s of a sin gle
tre a d c o nfig uratio n fro m a sin gle m a n u -
fa cturer. B M W t e sts a n d a p pro v e s
w h e el/tire c o m bin atio n s, b e gin nin g o n
p a g e 1 3 7.
D OT Q uality Grades
Tre a d w e ar
Tra ctio n A A A B C
T e m p erature A B C
A ll p a ss e n g er v e hicle tire s m u st
c o nform to F e d eral S afe ty
R e q uire m e nts in a d ditio n to th e s e
gra d e s.<

Tread wear

T h e tre a d w e ar gra d e is a c o m p arativ e
ratin g b a s e d o n th e w e ar rat e of th e tire
w h e n t e st e d u n d er c o ntrolle d c o n di-
tio n s o n a s p e cifie d g o v ern m e nt t e st
c o urs e .
F or e x a m ple , a tire gra d e d 1 5 0 w o uld
w e ar o n e a n d o n e - h alf (1g) tim e s a s
w ell o n th e g o v ern m e nt c o urs e a s a tire
gra d e d 1 0 0. T h e relativ e p erform a n c e
of tire s d e p e n d s u p o n th e a ctu al c o n di-
tio n s of th eir u s e , h o w e v er, a n d m a y
d e p art sig nific a ntly fro m th e n orm d u e
to v ariatio n s in drivin g h a bits, s ervic e
pra ctic e s a n d differe n c e s in ro a d c h ar-
a ct eristic s a n d clim at e .
Traction
T h e tra ctio n gra d e s, fro m hig h e st to
lo w e st, are A A , A , B , a n d C .
T h o s e gra d e s re pre s e nt th e tire's a bility
to sto p o n w e t p a v e m e nt a s m e a s ure d
u n d er c o ntrolle d c o n ditio n s o n s p e ci-
fie d g o v ern m e nt t e st s urfa c e s of
a s p h alt a n d c o n cre t e . A tire m ark e d C
m a y h a v e p o or tra ctio n p erform a n c e .
T h e tra ctio n gra d e a ssig n e d to
this tire is b a s e d o n straig ht-
a h e a d bra kin g tra ctio n t e sts, a n d d o e s
n ot in clu d e a c c eleratio n, c orn erin g,
hy dro pla nin g, or p e a k tra ctio n
c h ara ct eristic s.<
Temperature
T h e t e m p erature gra d e s are A (th e
hig h e st), B , a n d C , re pre s e ntin g th e
tire's re sista n c e to th e g e n eratio n of
h e at a n d its a bility to dissip at e h e at
w h e n t e st e d u n d er c o ntrolle d c o n di-
tio n s o n a s p e cifie d in d o or la b oratory
t e st w h e el.
S u stain e d hig h t e m p erature c a n c a u s e
th e m at erial of th e tire to d e g e n erat e
a n d re d u c e tire life , a n d e x c e ssiv e
t e m p erature c a n le a d to s u d d e n tire
failure . T h e gra d e C c orre s p o n d s to a
le v el of p erform a n c e w hic h all
p a ss e n g er v e hicle tire s m u st m e e t
u n d er th e F e d eral M otor V e hicle S afe ty
S ta n d ard N o. 1 0 9. G ra d e s B a n d A
re pre s e nt hig h er le v els of p erform a n c e
o n th e la b oratory t e st w h e el th a n th e
minim u m re q uire d b y la w .
T h e t e m p erature gra d e for this tire
is e sta blis h e d for a tire th at is
pro p erly inflat e d a n d n ot o v erlo a d e d .
E x c e ssiv e s p e e d , u n d erinflatio n, or
e x c e ssiv e lo a din g, eith er s e p arat ely or
in c o m bin atio n, c a n c a u s e h e at b uild u p
a n d p o ssible tire failure .<
Uniform Tire Q uality Grading
Q u ality gra d e s c a n b e fo u n d w h ere
a p plic a ble o n th e tire sid e w all b e t w e e n
tre a d s h o uld er a n d m a xim u m s e ctio n
w id th. F or e x a m ple :
Tre a d w e ar 2 0 0 Tra ctio n A A
T e m p erature A
D o n ot u s e re tre a d e d tire s. D rivin g
s afe ty m a y b e im p aire d b y th eir
u s e . T his is d u e to th e p o ssible v aria -
tio n s in c a sin g stru cture s a n d , in s o m e
c a s e s, to th eir e xtre m e a g e , fa ctors th at
c a n le a d to a d e cre a s e in th eir
d ura bility.<
1 3 3 n