Lexus88

Seems kind of odd to me that lexus would put 40 series tires in the front when the side wall is so much thinner than the back tires... 45 series tires actually have a sidewall equivalent to the rears... anyone try running 45 series instead??? did the car still look ok???

mitsuguy

iTrader: (2)

judging from your sig pic, I would guess you are talking about an IS...

if so, and you have staggered wheels, then you HAVE to maintain the same ratio as stock - by putting a tire on the front the same size as the rear, you will disable or render ineffective all of your stability control, traction control and ABS systems...

Lexus88

Yep... i guess i forgot to mention that i'm talking about the IS... the thing is, OEM sizes are 225/40/18 for the fronts and 255/40/18 for the rear... sidewall on the fronts would only be 90mm while the rears would be 102mm. the sidewall on a 225/45/18 would be 101.25mm... it would appear that 45 series tires would be a better match in front right???

edit: re-read your post and i see what u mean now...

i was hoping to put some 45 series on not only so that they would match better but was hoping to get a smoother ride... those skinny 40's in the front ride pretty harsh...

mitsuguy

iTrader: (2)

if you were trying to get the same size all around, yes, your theory would be right, HOWEVER, the computer is programmed for a diameter difference... if you were to put a 225/45-18 on the front, then the rear would have to be a 255/45-18... (assuming it would fit) the ratio has to stay the same...