Did a search and didn't find this exact thing discussed... Mirroring this question over here too as there's a lot of good knowledge spread btw'n all you.

255mm wide tires [17" diameter rim] all seem to have a recommended [or approved?] rim width of 8.5" - 10"; I never find good performance tires at a 255mm width spec'ed approving an 8" wide rim.

So what would happen if I try to put a 255/40-17 rim onto a 8" wide rim? I know the sidewalls will roll in more then the manufacturer recommends. But...
- will it adversely affect grip / performance in a noticable way?
- will it adversely affect life of the tire in a substancial way?
- will it look like crap, or at least 'odd' in a noticable way?
- will it not seal well? (this one I doubt but hey, I don't know)

Thanx for your thoughts...

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let's look at what you are proposing.

All of the tires will have the same overall diameter in order to not effect traction control ABS functions and such. That means that the front tire on a 17" wheel will have a 4.0" sidewall and the rear on an 18" wheel sidewall height would be 3.5". When cornering the front tires sidewall will have approximately 15% more deflection than the rear which will cause huge amounts of understeer.

Now, I know you have seen cars running 1" larger wheels in the back before and maybe that's what gave you the idea. The Corvette is the most glaring example of this theory but, not only is the rear wheel 1" larger but, the car is designed to run a rear tire which is also 1" taller which means the sidewall heights are the same

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BTW, to all the readers. I just wanted to clarify one thing for posteriry and for the benefit of the "library" nature of this board....

Luke here was mirroring an answer he posted to me on a different question; where I was questioning using a 17" dia front wheel and 18" dia rear wheel, with tires that would both make a 25" outer diameter.

The original question I posed here was also answered. So the answer to the 1st post above is

Thank you Luke for both answers as well as your patience. I hope other readers come across this and find it as valuable as me and learn as much as I have.

-steve

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So, would the same apply to the CLK430's which have different sized tires front and back?

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The CLK430 stock is the same as the C43. Both our cars have wheels and tires that have the same outer diameter, and practially the same sidewall [edit] height as well. Width is different front and rear, but the rest is held the same due to the rear tires being 40 series and fronts 45 series.

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