Can anyone comment on the effect of changing my stock rims to 18's with 225/40 tires on the fron and 235/40 on the back, oh and 7.5' wide at all four corners. I know this will result in a slight loss of poer, but I want feedback on overall diameter and handling. Thanks in advance.

 

http://www.miata.net/garage/tirecalc.html

 

Thanks...exactly what I was looking for. Any ideas on how these would perform compared to stock?

 

Very Poorly. If you are concerned about performance buy a lightweight 16". An 18" wheel is for flossn' on Boulevards.

First, you are migrating to a heavier wheel with a higher MOI. (It takes more work to get and keep the wheel rotating)

Second, you have increased the effective contact patch in the front, and decreased the effective contact patch in the rear. BAM! Your car now exhibits heavy oversteer.

Third, 235/35 series? You must have very flat roads in your neck of the woods.

Fourth, You've made no mention of the offsets. Unless the wheel is custom one-off manufactured for your car only, they are probably incorrect. Fiske is the only manufacturer in the world (to my knowledge) that builds a 18" wheel with the correct rear offsets for the S2000. Volk could make one, but the lead time is measured in months. For a 7.5" width, you will need at least +60mm offset. Good luck.

Summary, Don't do it.

 

Thanks for the input, but a few comments.

I never said a 35 series tire..that would be a little too low for me...even 40 series can be harsh in Baltimore.

How would this setup be reducing the contact patch in the rear? IT's staying the same. 7.5" all around.

 

contact patch and rim width are two different entities...

 

please explain....

and the tires are going to be 225/40 all around..

 

Contact Patch = area of physical contact between the tire and the pavement. (Where the Meat meets the road)

Wheel width = how wide is the hunk of metal holding the tires.

and the important one

Section Width = The Width of the tire tread. (example: 225/40/18)


How would choosing a wider wheel increase the section width of a tire? It doesn't.

Stock S2000 wheels dimensions: Front Wheels are 6.5" Rear 7.0"

If you can fit a 225/40 on a 7.5" 18 more power to you. The cross section would probably look like this: \___/ Instead of |____| Serious, its ghetto and possibly dangerous.

Back to the performance impact. Please re-read my orginal post. Its even more applicable if you go with four identical wheels at 225/40/18. Pay close attention to the parts about Tire Bias on the S2000 and the fact you are probably going to buy wheels with the incorrect offsets. A custom 17" could fit correctly and allow you to run a wider section width. More importantly, tires exist in the correct sizes.

Here is some extra though: (#2 above explained)
The W-Rated OEM 225/50/16 Bridgestone S02 is a non conforming tire. That is to say, Honda specifically requested that this tire be modified compared to the rest of the S02 line. What changed? They decreased the tread spacing to increase the contact patch for the tire size. Only the rear tires were modified in this manner though. When replacing the stock tires with another brand, I recommend purchasing 205/55/16 Front and 245/45/16 Rear to maintain the stock dynamic behavior.

There isn't a single reason in the world to run 18's on a S2000 other than to Bling-Bling.


[Modified by jerrypeterson, 2:47 AM 11/26/2002]