That sounds like an alignment issue, also some tire models are more prone to wander. Our car lowered, with lots of camber, and 15mm spacers on the oem fronts wandered badly with worn Michelin ps2's, but is 100% more stable and planted on RE71Rs.

 

Sorry to pull up an old post however I recently purchased a 2008 997TT with brand new Yokohmas F 245 30-20 & R 305 30-20 and after roughly 2500kms I blew out the front diff..Not a fun repair. Repair is now completed and I am going to replace all the brand new Yoks with Michilens 245 30-20 still up front but change the rears to 325 25-20. I have HRE rims and measured them and they appear to be 12" so I am thinking this should be a safe combonation? Really don't want to replace another diff and would like to stick with 20"s ...

 

http://www.1010tires.com/Tools/Tire-Size-Calculator

This should help. 325/25/20 is within 2.37% of the front tyre diameter. Not perfect but below the 3% threshold that gets mentioned often.

 

No problems with 245/30/20 MPSS and 325/25/20 MPSS in 20K...

 

I am running HRE P40 SC wheels with the following specs:
(my car has PCCBs)

20 x 9 with 245/30 PSS Fronts
20 x 12 with 325/25 PSS Rears

 

Sorry for the stupid question why will this overheat the diff. There are a few members running the 305’s on 20’s does it matter how you drive cause i drive like grandma!!! Lol but true! I don’t track or race my car in any way shape or form.

 

Hey all,

I am in need of some tire advice as well. I have CCW wheels in the following sizes: 20x9.5 with 245 30 20 in the front and 20x11.5 with 305 25 20 in the rear and currently running Hankook Ventus 12 Evo 2's. is this the incorrect size? should I be running 325's in the rear as well or are these tires within the 3% limit? If not what tires are my options to match my current front tires.

 

After blowing my front diff due to wrong size tires on 20" rims I am now with and have been for some time 245/30/20 front & 325/25/20 rears (Pro Pilot Sports). This is what was recommended and I have had zero issues and the car rides and handles impecable. Plus the setup just looks amazing. I don't track my car or at least have not yet but for weekend spirited road driving it works great.

 

 

Great thread. I just stumbled on this. I was having this exact same discussion with a friend of mine. I have the Techart 20x9 in front and I believe 20x12 wheels on the back running 245/30 front and 325/25 rears. On my track days I was feeling like my front tires were hopping a little. Come to find out they were out of balance. Anyway, I noticed I was running PZeros tires which have 26.5 diameter on front and 25.8 diameter on rear. A tenth bigger deviation than what I'm seeing with the Michelin's. He was saying my diameters need to match exactly or I could have differential issues but from what I'm reading on here, as long as they are under 3% deviation I should be ok? I may ultimately switch to Michelin sport cups but will wait till these wear out.

 

Safe and Proven tire sizes:


235/35/19
295/30/19


235/35/19
305/30/19


245/35/19
295/30/19


245/35/19
305/30/19


245/35/19
325/30/19


255/35/19 *provides most sidewall option
325/30/19 *provides most sidewall option


245/30/20
315/25/20


245/30/20
325/25/20


245/30/20
345/25/20

 

Okay so I gather I need new rear tires for sure. I do not see a match for the Hankook tires in 325 width to match my 245 fronts. Can I get a different brand to match the front? I see Pirelli, Toyo, and Michelin have this size available.

Also what type of sound are you all hearing with the "differential overheating"? In my car I believe I hear what sounds like the differential making a rubbing sound the longer I drive or the harder I drive. I'm not driving my Porsche much lately while I'm trying to resolve this issue btw.