I have a 2005 911 997 c2 and have currently on it c2s 19 inch rims on it with snows on them. Since its not the wider body it fills out the wheel well and fender.
They are
235/35/19
295/35/19

Now the question.

I am going to use these rims as track rims and have purchased the pilot sport cups for these
rims but 305/335/19 for the rears because they weren't avail for in the 295's....the shop says they will be fine and perform well??? Will this size change affect anything? Will it be fine? Also my cars not the wider body?

 

Giving up 10mm won't make a massive difference unless you are a super driver and really looking to get every last possible drop of performance out of the car in a competitive format.

Also if you are looking for tires specifically for the track why not slap on a set of hoosier's?

-Tim

 

You likely won't notice a difference.

 

I think it will be fine..10mm isn't much. I also run into the same issue since the tires I want don't always match the stock sizes.

 

What is the wheel width? It shouldn't be much of a difference in terms of feel because its in the rear. You may end up having to run slightly different pressures than you were before.

 

What's the wheel offset? You may also need to check clearance with the inner wheel well at the front under full droop. Just jack up the car, rotate the wheel and see if you can hear it rubbing.

 

The sizes you show will all be fine on 11" width wheels. No effect on the car, imperceptible effect on grip.