18" Turbo wheels

[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

[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

[computamedic]

Sunil,

Your calculations are correct - but it's only a 1.09% difference, not enough to worry about. For 18" wheels the 225/40 and 265/35 tyres are correct.

I'm sure that's the conclusion we came to on Sunday.

Regards

Dave

[Diesel130]

Great. Then you'll be able to go 1.09% faster in each gear (apart from top gear), but take 1.09% longer to get there !