Mozi

Hello all, I would appreciate your feedback in this:


My goal is to improve handling and balance as well as reduce understeer as much as possible. This is all for significantly spirited road driving and some street racing.

F 245/40/18 R 255/45/18

F 245/45/18 R 255/45/18

F 245/45/18 R 245/45/18

F 245/40/18 R 245/45/18

F 255/45/18 R 255/45/18

Can you talk to the advantages of each? I am trying to understand how the slight variances in the combos act on my goals.

Thank you,

MoZi

ares

iTrader: (2)

245/45/18 255/45/18
235/45/18 255/45/18
235/45 18 245/45/18

not all of those were on there, but Id include those 3 as my top choices. Id probably go with the 2nd one 235/45 and 255/45. keeps the stagger and improves traction all around, wont help with understeer though; for that go with one of the other 2.

Mozi

Thanks ares. As usual, you always reply to me newbie posts

What difference is there between the other 2?

What would having a "40" middle number in the front tire change in terms of handling, cornering or understeer?

Why did you recommend that choice?

Thanks again,

MoZi

D'oh

245/40-18 Front
245/45-18 Rear

245 = Tire tread width (approximate)
40/45 = Sidewall ratio (percentage of width)
18 = wheel diameter

These sizes improve the balance by using the same width tire, and are very close to the stock tire stagger so the TCS/VDC systems behave normally. Also, there are usually many tires available in those sizes. (Plus, that's what I'm running right now)

-D'oh!

Mozi

Thanks D'oh,

I am curious as to the difference in performance, hadling, understeer between what you recommend and the same but with 255s in the back. Another question, does the stagger come from the 40 and 45 difference in what you recommend?

MoZi

D'oh

Yeah, the stagger comes from the difference in profile.

Both use 18" wheels, and both are 245 wide. However, the fronts have a sidewall height that is 40% of 245 (or 98mm = 3.85") and the backs have a sidewall height that is 45% of 245 (or 110mm = 4.34").

I don't know if the difference would really be that significant between the two setups. I've never run a 245 front 255 rear so I wouldn't be able to say how they compare. All I know is that the 245 front and 245 rear has balanced the car much better in dry conditions that the stock setup.

-D'oh!

2003z

iTrader: (7)

I would go with D'oh!s recommendation. 245/40 front 245/45 rear. Keep the factory size difference, but have the same widths. I am going with these sizes for my lapping day tires. I run 16s at the strip, 17s at autocross and 19s on the street. 18s for the track only, and temporarily til my 19s get back from iforged.

ares

iTrader: (2)

having wider in the back as I posted would cause understeer, being that the backs are grabbing harder, but with 255 you do get a slight benefit in the launch.

Mozi

Ok, so conclusion would be that 4 same size tires (width) would reduce understeer most from a tires pespective, yet the 40/45 would ensure in keeping the VDC working properly.

What about 255/40/18 F and 255/45/18 R as opposed to what D'oh! recommended? What would be different?

MoZi