RickBetterley

I run a 993 on the track in red run group; car is built up as a club racer but I don't race it.
I currently use Hoosier R6 tires in 285/30/18 sizes on the rears, 245/35/18 fronts. The tire diameter is 24.9."
We might want to change to a diameter of 27.7" to move the speeds up in each gear (car has a very close ratio gear set).
I like Hoosier R6 tires, but am not sure if I can get this diameter in a size that will fit my car.
I realize that a larger tire will (all things being equal) mean slower acceleration in each gear, but the gears are low enough/close enough that I should be OK.
So - I guess I am looking for comments and reactions to this idea.
Thanks

Bill Verburg

If yours is like mine 280/30 x18 is a very tight fit when the car is at a good height. Put a tire 2.8" taller and you will have issues

You really need to address the root cause of your dilemma, ie change your transmission gearing or I suppose that if you like the current drops you could use a cwp set w/ taller gearing, I don't know if any are available.

Maybe you can swap transmissions w/ someone the wants one the way yours is setup

RickBetterley

Hi Bill
Thanks for this reply; you are always a good source.
I think you are right about fitting taller tires; we have decided to stay with the existing diameter and have changed gears 3 through 6.
Let me know if you would like the details.
GBox was great; Stan described the existing ratios as a hillclimb box!

Bill Verburg

It would be interesting to see what you have, let me know the gearing, rpm and tire specs and i'll run the #s for you