930man

I am Having trouble finding a tire compound for the new 997
Porsche has changed the size on the new car. The tire size is
235-40 -18 front
265-40-18 rear
I cant seem to find anything that will keep the same ratios from front to rear.
Has anyone seen anything or help me convert the sizes to a optional avaible size?

craig001

Here's a good site from an earlier post I made on the 964 boards: http://www.chris-longhurst.com/carbibles/index.html then go to the Tyre Bible. Actually all the Bibles are good reads.

930man

thanks craig will try it

930man

fantastic information
thank you very much i can now figure appropiate tire sizes

Joe Weinstein

Actually, you'd better take it with a grain of salt, at least the (or any) online tire dimension
calculator. The numbers purport to mean what that page describes, but in fact they only
get you in the general ball park. If you have *any* clearance concerns, or you want to
really know how much rubber you have on the road, or whether your speedo is going to
be accurate, the *only* accurate info for a given tire's dimensions is the manufacurers tire
spec sheet, eg:

http://www.tirerack.com/tires/Spec.j...omCompare1=yes

I have seen the diameter of two identically-specified tires (245-45-16) differ by over .25"
from the *same* manufacturer! These were different model tires from Firestone...
Tread width (the amount of rubber on the road), section width (how far the sidewalls
bow out towards the shocks and fenders) and diameter (speedo and fender clearance)
are all significantly variable from brand to brand for a given tire 'size', so beware. Find the
spec dimensions for the tire you use now so you can compare them against any other you
may be considering.
Joe Weinstein

Joe Weinstein

Oh, and when it comes to R-compound competition tires, the possible variance is
maximum. For the standard comsumer market there is more conformity (but still
not enough to lift the warning) but for DOT tires or racier, the differences can be
substantial.