I have gone through all of the threads and can't get a straight answer. I have a 2001 996 turbo lowered with H&R springs. My friend gave me a set of 19" techart formula wheels. Rear are 11" front are 8.5". I was told to put 315/25 on the rear and 225/35 on the front. Does anyone know if these sizes will work? Also the front size is smaller than the stock 235. What should I do?? I spoke to techart and the offsets are proper for a 996 turbo.

 

With the recommended tire sizes, the front tends to be a little bigger than rear. I've read this prevents the front wheels from spinning more than the rear to protect the front diff. Tirerack will recommend 315/25r19 and 235/35r19 all day long.

 

Sorry to say, but it is way more complicated than just picking width and profile. Do a search before you buy any tires. Not all 315/25/19 and 235/35/19 have same rolling diameter, which if not paired correctly, may cause diff. damage

 

Thank you any input is appreciated.

 

235 35 19 and 315 25 19 is fine.

 

There is a lot of debate on this forum about tire sizes and blowing diffs. A few guys have blown their front diff and many people believe its a direct result of the tire sizing. Not saying it's not but nobody really knows for sure. They are viscous diffs which blow for no reason after all. (lets not start this debate here please)

Stock Tires: 225/40-18 & 295/30-18. 803 & 807 rev/mile 0.5% diff.
Closely match in rev's per mile small % diff between F & R.

235-35/19 & 315/25-19. 791 & 800 rev/mile 1.1% diff.
This is very close to the stock setup. The 315 is getting really hard to find these days so a lot of guys are running other sizes.

235/35-19 & 305/30-19. 791 & 769 rev/mile 2.8% diff.
This is my current setup and a lot of guys run this. Tires are cheap and easy to find. Many don't like the differential as it's too close to the mythical 3% maximum we're told is the ceiling.

245/35-19 & 305/30-19. 783 & 769 rev/mile 1.7% diff.
Closer to stock and will likely be my next tire setup. These are also cheap and plentiful, guys have run them on lowered cars with no issues up front.

225/40-19 & 295/30-19. 773 & 776 rev/mile 0.5% diff.
Another member just bought this setup and was really happy with it, read here. This is basically stock size match, but in 19s. Many members when buying tires want wider, but thats just preference.

Personally, I really like the 305 rear tire, has meat looks great and rides comfy plus a little wider than stock. Matching a good front to it is the trick, the 245 seems to be the best choice and will be my next tire. I'm not overly worried about the diff issue but that's my own personal choice based on my personal racing / mechanical experience.

Another options courtesy of Feelgood MD (thanks)
225/40-19 & 305/30-19. 773 & 770 rev/mile 0.5% diff
The beauty of the 225/40-19 is that you have the option to run either 295/30-19 -OR- 305/30-19 which may be convenient for members struggling with availability, price, or width preference. Personally, I have an extra set of 305/30-19 PS2s sitting in my garage. I like knowing that once I burn through the 295s I can mount the extra 305s with the existing 225s up front and not have to worry about diff issues.

Here is a nice compare of 315 vs 305 ssmugen did:


My 305 rear..

 

Excellent, KJ! Putting aside the debate over the legitimacy of the infamous differential issue, that is the single best summary of available sizes for 19s on a 996TT I've come across. I had to wade through tons of threads over the last couple months to derive all that info that I just read in 20 seconds on your post. I wonder if you should repost that into a new thread and call it "official tires sizes for 19s" or something and maybe they'd make it a sticky or put it into an existing sticky.

As you know, I'm the guy running 225/40/19 and 295/30/19 that you referenced above. I'd like to add one additional option that I discovered during my research that no one has previously talked about:
225/40-19 & 305/30-19. 773 & 770 rev/mile 0.5% diff
The beauty of the 225/40-19 is that you have the option to run either 295/30-19 -OR- 305/30-19 which may be convenient for members struggling with availability, price, or width preference. Personally, I have an extra set of 305/30-19 PS2s sitting in my garage. I like knowing that once I burn through the 295s I can mount the extra 305s with the existing 225s up front and not have to worry about diff issues.

Again, great write up and thanks for your input into my thread dealing with the same issue.

 

I believe rev/mile is different for each tire vendor, not just size, correct? For example, not all 315/25/19 will have the same rev/mile, right?

 

yes, but they're pretty close to the theoretical figures you find on the tire calculator websites. i double checked before i put on my pilot super sports and they were fine with the aforementioned sizes. they're all published on tirerack . com and michelin . com

 

I believe you're correct, but the percentile should remain as long as your not mixing F&R tire manufacturers. A 0.5% differential should be the same from Bridgestone to Michelin, but could differ if you had one brand front and one rear. Well, that's the idea anyway..

 

I added your options to my list (with creds of course) as to keep the options together in one post should somebody down the road find this info

Agree maybe another thread with the tire options in it would be a good idea, however I cringe at the debate over the diff issue. Tires are like oil, hotly debated with very strong opinions on each side.

 

To make a long story short, I needed new tires and was tired of buying PS2s due to the cost, but I couldn't find another 315/25/19 & 235/35/19 combination that had acceptable % differences. If anyone has tire brand and size options for 19x8.5 and 19x12, I'd be more than happy to hear about it. These PS2s are getting expensive.

 

One other option to note is 235/35/19 up front with a 295/30/19 out back. I currently run this size in Hoosier R6 tires with good success.

 

Great thread, was looking for some feedback.

Finding tires does not appear to be easy. Currently running Nitto Invo 315/25/19 and 335/30/19. Front have life on them, but can't seem to find Invo's in 315 for the rear.

Contemplating a move to Michelin Super Sports in the following sizes.

245/35/19 with a rolling diameter of 807 for the front

and

305/30/19 with a rolling diameter of 792

Seems like this combo should be safe as it under 2% difference in rolling diameter with the front being the larger of the two. Some concerns with the 245 in front as I'm at GT2 ride height.

Appears as if the existing fronts could definitely last through another set of rears, but I have no experience mixing tires, does this make sense ?

Thanks.

 

As I have posted in many threads,,
I have measured tires on the stock rims..
The rim width is usually not the size of our cars with the tire specs.
Fact,,, A narrower rim will make a larger O. D. AND a wider rim will make a smaller OD with the same size tire.. Usually about 1/4''OD per 1/2'' rim. size.
Also as I have posted before,, I have run fast and long for over 20,000+ miles with 1/2'' difference with Zero problems and had Porsche Techs agree no problems either with that.
Just sharing my info.