Ok it seems my front differential/viscous coupling is chewed as I have put winter tires on my Cargraphic 19's and they are a differential profile to the the summer ones, a similar issue to trying to put 997 TT wheels on a 996 TT it seems, you can do it but soon or later you will also knacker the 4WD drivetrain.

 

What sizes winter setup have been used?

 

Ray it seems the Rear doesn't matter, I have had both 315/25 ad 305/25, the rule is simply for the Fronts don't go anywhere from 235/35's. Any experience with yours, what sizes have you got on your Cargraphics, ever had any winters ?

 

WHAT SIZES AND BRANDS WERE YOU RUNNING front and rear?

What matters is the mis-match between front and rear, not the absolute size of the fronts...

I'd heard you want to be within 0.3" in total tire diameter between front to rear....curious as to what your mismatch was that led to the diff issue...

A

 

My TT is running conti 235-35-19, 315-25-19 now. And the pevious owner ran 295-30-19 at the back. When I do the calculation, 295-30-19 is 1" full inch taller than stock 18" and my 315 is 0.3" taller than stock. I know he ran that 295 setup since new and from the service record, it don't have any problem. So with your 315 or 305 setup, it shouldn't eat up your diff.

 

tvm Ray for your input, my problem is that it seems I do have something other than 235/35's on the front and I won't know this until tomorrow am as all my docs are in the car, hence where my problem lays, the front axle.

 

everything matters (front and rear). Post the complete tire spec, front and rear.
(brand, model, and size designation). The relative diameters are what matters.
Then go to www.tirerack.com, and look at the specific spec sheet for these
tires to see the actual diameter. I want my tire diameters to be equal to within
a few tenths of an inch, and if any difference, I much prefer the fronts to be
the taller.
For this viscous system, though, the closeness is the crucial part. Otherwise it's
like letting your clutch slip all the time. Quick burnout guaranteed.

 

Joe,

You really need to post more often, bro. You're a wealth of good info.

 

I recently bought a set of HRE's made for a 997TT. 19x9 and 19x12....
I spoke with HRE before purchasing to make sure there is no issue with rubbing or otherwise. They said I should be fine with my tire sizes and fitment with my PS2's.

I put my PS2's on them 235/35/19 and 315/25/19... I only have around 500 miles on them total....

Do you guys think I will run into this issue too or am I ok?

 

You will be fine. With those tires, the revs per mile are 817 front and 824 rear, so within 0.8%, which is practically ideal.

 

So from PS2 specs (every tire CAN have different specs, even with the same nominal dimensions)

#1. 235/35-19 is 25.5 inches - revs per mile 817

#2. 315/25-19 is 25.2 inches revs per mile 824

#3. 295/30-19 is 26.0 inches revs per mile 799

You can see that running the first and last will cause the front diff to run ~ 2.5 times as much as #1 with #2.

Note that stock sizing has only 3 revs per mile difference... so the 18 revs per mile (on #1 with #3) is 6 times the stock size.




A

 

I've got a front dif and drive shaft for sale if anyone needs it. :0

 

if you put stock 08 turbo wheels and tires on a pre 05 turbo will you have trouble with the front rear wearing out?

 

I believe that's more of an offset issue, you will need spacers.

RD

 

when mine went I went to RWD.