bocallaghan

So I have aftermarket rims on my car and the change in tire and rim size to 20's all around has altered my traction control at higher speeds. I have 305 25ZR 20's on the rear. I don't want them any wider if I don't have to, but I would like them taller to help offset this problem and fill out my fender well. Would increasing to a 315 35R 20 reach my goal or would it not work. Thanks for your suggestions.

JoesC5

Need to know what size tires are on the front to be able to suggest what size tires on the rear would work.

Bill Dearborn

The taller tire has to be on the rear to avoid TC problems. It should be at least a half inch taller than the front tire to avoid issues. You can solve the problem by going with a smaller front tire or a larger rear tire.

Bill

bocallaghan

I have 255 30ZR 20's on the front.

Thanks.

JoesC5

Your 255/30-20 on the fronts are 26.02" diameter. A 305/30-20 on the rear would be 27.20" diameter and would give you the 4.3% front/rear bias you need.

On my stock Z06 my fronts are 25.58" and the rears are 26.68" with a 4.1% bias..

m R g S r

I have a .55" difference if I remember correctly with no problems. 275/35/18 and 295/35/18

bocallaghan

hmmm I wonder why I'm having problems. It only happens at a speed of roughly 65mph and above. The traction control active light comes on at these speeds and I have to turn off the TC to remove the light and be able to accelerate. I do like my TC and don't like to turn it off unless I have to. What else could cause this problem? Thanks for all your replies!

JoesC5

Your fronts are 26.02" in diameter and your current rears are 26.00" in Diameter. The rears have to be slightly(around 4%) larger in diameter then the fronts. That is why I recommended the tires I did as they are ~ an inch larger in diameter then the rear's currently on your car. Another tire that would work would be a 295/30-20.

bocallaghan

Oh okay, I misread your first post, I thought you meant that my rear tires were currently at at 27.2" diameter. Your two tires sizes is exactly the information that I'm looking for. Thank you so much JoesC5!

JoesC5

Now you just have to find a tire in the new size that's the same brand/model as your fronts. Good luck. I don't recommend mixing different brands/models.

haljensen

Here's a site that will help.

http://www.1010tires.com/TireSizeCalculator.asp

Bear in mind that every tire company has their own way of measuring their tires so the calculated diameters won't be exact.