KirkF

Hi,

I recently replaced all four tires on my 1989, 964 C4.

The car is fitted with 17" Speedline rims, and slightly lowered with a Bilstein shock kit. I had Michelin pilot sports on it before.

The same model of pilot sport wasn't available, so after looking through the forums I decided to go with the Continental tire other posters were happy with. And I just ordered up the exact same size as the Michelins.
However as soon as I put the tires on, I immediately noticed that something was wrong. The AWD system is reacting to the tires, and kicking in its lock solenoids. (Not pleasant). I put on my winter rims and the problem immediately went away. (I guess I am out by more than 6% front to rear rolling diameters?)

The tires I put on were:

Front:
Continental ExtremeContact DW Tires 225/45ZR17 91W 340-AA-A
Rear:
Continental ExtremeContact DW Tires 255/45ZR17 98W 340-AA-A

So now the question is what to do. Does someone know how to find out the actual rolling diameter of these tires?
I'm thinking maybe I could replace just two of them to get myself back in sync. Even if it means going to a different brand for front / rear?

Opinions?

Thanx!

Kirk

breljohn

That's way off...
Front should be 205/50 and rears 255/40 if you want to keep a "factory" fitment

Ken D

As you've probably figured out, the rears should be 255/40, not 45. TireRack's website will list the diameter of the tire (click on the 'Specs' tab).

http://www.tirerack.com/tires/tires....remeContact+DW

Andy Roe

Yeah, the rears are wrong. For the front the standard is 205/50 as suggested above, but on a C4 225/45's can help reduce understeer a bit. I'd just change the rears to 255/40's and you'll be set.

panicosc

I got Toyos on mine, front 225 - 45 - 17, rear 255 - 40 - 17.
No issues at all.
Im about to put new set of tyres very soon, Michelin PS2 or PS3, not sure which ones yet.