vern1

I have to replace my tires. Looks like the Sumitomos are the way to go. I searched but didnt find the answer to this although i am sure it is in here somewhere.

If i want to keep the stock rims and go with wider tires than the 205/255 purely for cosmetic reasons, what is the most practical upsize? And are there any downsides to this? Should I just stay with the size i have now? This is a street car only and has been lowered (dont know if it is ROW, RS height or what as it was done by the PO).

Thanks

timothymoffat

Fronts are easy, a 225/45-17 will fit the 17 x 7 wheel fine.
Rears are a bit more tricky because you will more than likely have an effect on overall gearing. 275/40-17s would probably be fine on the 17 x 9 rear but would make your gearing taller. Not desireable in a car who's gearing is already too tall (IMO).

If it were me I'd go with 225/45-17 front and stay with 255/40-17 rear. If you track or auto-x this should reduce understeer slightly as well.

vern1

excuse my ignorance but if you are going from a 255 to 275 but staying with a 40 series profile, how would that effect gearing?
thanks

timothymoffat

Remember the "40" is an aspect ratio. A percentage of the tread measurement. So by increasing your width and staying with the same aspect ratio you're getting a (slightly) taller tire.

vern1

so could i go with 35's with 275? or some wider lower profile backs?
thanks

bart1

Timbo is right on.

vern1

ok so there are no wider tire options for the rear Cups that make sense

i am surprised by this

thanks

vern1

come on guys. i have seen a myriad of options discussed for 18" wheels but there really are no good wider tire options for 17's??
thanks

timothymoffat

Just had a quick look for a 275/35-17 on Tirerack. No results. Kind of surprises me as well.

vern1

is there anything in a 35 or 30 width that would make sense?
thanks

Martin S.

I ran the 205 and 255 stock combo; they worked great. Porsche engineers figured the optimal tires sizes out....they plenty smart over there. Just stay with stock....you are not tracking the car...they'll be fine...and cheap too!

vern1

it was going to be purely for cosmetic reasons not track. i just prefer the look of wider tires and was trying to find something that would work
thanks

Martin S.

Cosmetics....now we are talking. My car is all about cosmetics. See Grand Prix white NB 993 covered in Blue Painters tape.

235/45/17 front and 275/40/17 rear...this is the combo I use from Toyo with their RA-1 tires...of course these fronts are NLA from Toyo

You need to exercise caution on the rolling radius delta front to rear. You cant just ***** nilly put a set of random tires on your car. The front to rear rolling radius delta should not exceed 3%. If you e-mail me mfschacht@gmail.com, I will send you an EXCEL spread sheet that allows you to calculate the delta in a matter of seconds. This offer extends to any and all.

The consequences of a rolling radius delta mismatch front to rear, the ABS will shut down. You do not want this to happen. And I agree, Big Meat looks cool.

Martin S.

Cosmetics....now we are talking. My car is all about cosmetics. See Grand Prix white NB 993 covered in Blue Painters tape.

235/45/17 front and 275/40/17 rear...this is the combo I use from Toyo with their RA-1 tires...of course these fronts are NLA from Toyo

You need to exercise caution on the rolling radius delta front to rear. You cant just ***** nilly put a set of random tires on your car. The front to rear rolling radius delta should not exceed 3%. If you e-mail me mfschacht@gmail.com, I will send you an EXCEL spread sheet that allows you to calculate the delta in a matter of seconds. This offer extends to any and all.

The consequences of a rolling radius delta mismatch front to rear, the ABS will shut down. You do not want this to happen. And I agree, Big Meat looks cool.

vern1

Martin, are the 235/275 combo on your standard Cup rims? Any adverse effects?

I had considered going to 18's but i couldnt honestly find another set of rims that i liked that much more than the Cups to spend all that extra dough.

Therefore will likely stay with the Cups and new tires and get the Cups refinished

thanks