wheel size change =speedometer off?

[jukka]

I've seen some beautiful wheel/tire pictures on this forum! I was just wondering what happens when one changes to a 16" wheel, does this not screw up the speedometer and how do you compensate for this?

[pdupler]

For the most part, we just choose a tire size that comes close to the overall diameter of the stock tire and live with it. 5% more or less isn't much a concern. There are lots of tire size calculators on the web, plus if you go to tirerack.com, it gives you the exact tire diameter for every tire in the catalog so you can compare.

[ma615mgte]

im suprised you didnt post the link.. http://www.celicasupra.com/wheelsaftmkt.htm

[CJSREDPRA]

:stupid:

Yep, for those of us that DO want to retain a accurate speedo without having to jump through more hoops, we start looking at equivelant tire sizes. Myself & Phil are running the same tire/wheel combo & this what we did to retain our speedo readings:

Stock wheels/tires: 14 x 7"/225/60/14.

Aftermarket: 16 x 8" (Compomotive CXN's) / 245/45/16 (Yokohama AVS Intermediates (discontinued)).

Can't remember what the equivelant size would be if you stepped up to 17" wheels (width's will vary if you want to do a staggard size. Myself & Phil kept the same sizes on all 4, so that we can do tire rotations).

In the case of stepping up to a 245/45/16, there are a few tires around, but the choices are somewhat limited. 245/50/16's, there seems to be more choices. On a recommendation from Don Lew, I went with this size to maintain speedo acuracy. And it's still correct between my 2 sets of wheels/tires.

[Supra GTR]

245/40R17 is the equivalent OD size in 17"

Regards,
James R