citychap26

Hi All,

I bought a set of 18" Turbo alloys which I hope to fit to my 993 C4. I'm not sure if they are "real" Porsche alloys, they have the following in the inside of the wheel STTI and a number starting 993.xxx.xxx.xxx (where xxx are other digits)

The wheels are fitted with 225/40/18 and 265/35/18 P Zero N3 tires.

Now I have put the 18's next to my original 17" Cup 2 wheels and they appear to be bigger, IE from the ground to the top of the tire.

What's going on ??? I thought that the tire sizes are correct for a 993

Any help appreciated.

Cheers

Sunil

jimbo3

Your 18" tire sizes are correct and it's the tire size that matters when looking at overall height, not the wheel size. You didn't mention what size 17" tires you have, but maybe they're too small. Go to <tirerack.com> and compare circumference on your 17" tires to the 18's. Should be close.

BTW- The rear Turbo wheels won't fit a C4 as the offset is 40 and the C4 needs 65.

Garth S

With that rear tire size (265/35R18), it is more than likely fitted to the correct NB offset of ET65, which will be found on the rear of the wheel and cast near the valve stem = Porsche OEM wheels with the 993#.
Tire diameter should be 25", and with 18's, the car should also have the cross brace bolted to the steering rack. I have a spare brace, if anyone is looking ..

citychap26

Hi All,

Following the example on tirerack.com the 18's do have a greater overall diameter:

17" Calc:

255 * 0.40 = 102
102 * 2 = 204
204 + 431.80 (17 * 2.54) = 635.8

18" Calc:
265 * 0.35 = 92.75
92.75 * 2 = 185.50
185.50 + 457.20 (18 * 2.54) = 642.70

Cheers

Sunil