if so, what are you running up front ?


to everyone else with 19" wheels , what size rear tire are you running (besides the stock 305/30/19) ?

WOULD A 325/30/19 work with a 245/35/19 (michelin pilot sport cup) on a 997tt ?

 

I think you will find more information if you search for "325/30-19". I remember lots of people thinking about running 325's in the rear but I do not remember anyone actually doing it. Last time I looked, there was not a good front size to match the 325's. Anything wider than 245 in the fronts can rub. Make sure you keep the front/rear diameters very close to stock.

 

would 305/35/19 fit rears??

 

I do not think it would be a good choice because it is 4.6% larger than stock. There are two important factors when changing the tire sizes on the 997TT: 1) the difference in size (circumference), and 2) the front/rear ratio; you need to keep both pretty close to stock.

The stock rear tires (305/30-19) are 2.9% larger than the stock fronts (235/35-19). A while back, the consensus was that the sizes (circumferences) should be within +/- 3% of stock and the front/rear ratio should be within 1% of stock, keeping in mind that the stock ratio is not 1:1. It makes it pretty tricky to change the tire sizes.

 

Great advice - if you get the too large a difference you put undue strain on the AWD differential and could damage it.

 

Yes you will eventually damage the AWD system and it is not worth the hassle!!

 

I'm running 325/25/20 and 235/30/20. Car runs perfect. 50K.

 

I'm pretty sure this discussion is only about 19" tires. But you are correct, those fitments in 20" are fine.

 

Yeah - OP was asking about 19's. OEM 305/30-19 and 235/35-19 have a diameter difference of 2.8% (OK). 325/25-20 and 235/30-20 have a diameter difference of 3.2% (on the high end of acceptable) and the OP's setup of 325/30-19 matched with a 245/35-19 would have a diameter difference of 3.5% (again on the high end - I'd be worried).

 

actually
325 30 19 and 245 35 19 michelin pilot sport cups.

 

If you have time, this is an old post. I realize the sizes are different but it's good information. Seems to be consensus that 3% or less difference is OK.

https://www.6speedonline.com/forums/...15s-rears.html

 

a 245/325 set up is 3.5%.

 

I just wanted to add another bit of information. My summer front/rear ratio is 0.97 ratio and my winter front/rear ratio is 0.98. The car is set-up to tolerate a little larger (3%) circumference tire in the rear. It also does fine with the Porsche recommended winter tires, which are 2% larger in the rear.

I just don't think you are going to find an acceptable combination using 325's on 19's.

Summer: 305/30-19 and 235/35-19
Winter: 295/30-19 and 235/35-19

 

im currently running 305/30/19 at rear!!! n it works perfectly fine!! I heard running wider then 325 would affect the performance

 

305/30/19's are stock sizes so they better work perfectly fine.