Wheel upgrade

[02Z28]

hey, does anyone know of any place or chart online that will let you know what size tires you will need to keep the speedo accurate if you are changing rim sizes?

[Dave M]

try this:
http://murray.faithweb.com/formulas.htm#tire_diameter

[02Z28]

thanks....do you know the widest wheel/tire that will fit up front on my 02 Z28 without it rubbing during turns?

[Firebird8798]

you can go pretty big..on my dads z28 he has 315 in the back and 275 in front.

[02Z28]

i'm guessing that's with a fairly big offset up front, tho, right?

[Injuneer]

The stock wheels are 16x8 with a 55mm offset. The stock tire diameter, assuming you started with the 245/50-16 tires is 25.65".

The problem with the 16" wheels is that there aren't many high performance tires made in big widths.... the largest you are going to find is a 255/50-16... not much of an increase. The impact on the speedo is small. You might find a 275 width in some of the low end tires, but that's not what you want on a performance car.

The typical upgrade is to 17" wheels. The WS6/SS wheels are 17x9 with 55mm offset. That allows you run a 275/40-17, which has a diameter equal to the stock tire size, or a 285/40-17 which has a small impact on the speedo. Most of the aftermarkets are 17x9.5", and you can live with offsets in the range of 45 - 56mm.

If you want to go to 315's in the back, you need a 17x11" wheel, with a 45 - 50mm offset. That just barely keeps the 315/35-17 tire under the fender. And the 315/35 has the same outer diameter as the stock tire.

I have the AFS ZR1 replicas... 17x9.5 56mm offset with 275/40-17 BFG KDW in the front, and 17x11 50mm offset with 315/35-17 BFG drag radials in the back:

[02Z28]

cool....good info there, thanks

i was mainly trying to figure out what would fit up front without rubbing, both on the stock wheels and on bigger ones, cause i'm gonna keep the front & rear tires the same size for rotational purposes.

on the stock rims, i'll prolly go with some 245/45-16's. i'd rather the speedo say i'm going faster than actual speed instead of slower...plus, the slight decrease in wall height over stock will look better than a slightly taller one, IMHO....not to mention, it will stiffen up the sidewall flex a little.

then when i upgrade the rims, i'll prolly get either 17's or 18's, with 275/40-17's or 275/35-18's

[hotwhip9]

i have 285 40 17's, on 17x9's all the way around, in the back is no problem, in the front it rubs a little bit when cornering really hard. i have to devise a way to pull the inner plastic piece of the fender forward,i have a good idea but am too lazy to do it.