malem

Alright looking for a little info as im entirely new to the porsche game and from other threads i have picked up that you can mess up the Differential with to much of a difference in overall diameter from front to rear wheels...

I recently purchases a set of wheels

19x8.5 + 40
19x12 + 65

what size of tires would you guys recommend..

Thanks in advance..

Cheers
-Rhys

Capt. Obvious

I'm assuming you have a Carrera 4 or 4S since you're worried about AWD tire size matching. If your car is not all wheel drive, you have nothing to worry about.

For tire sizes, you have several options.

I have 19x9.5 and 19x12s on my car and I run 235/35s and 295/30s.

235/35 and 315/25 is also an option.

As is 245/35 and 295/30. Howeve, I would not run this combo on your wheels because the front tires will have a slightly "ballooned" sidewall, while the rears will have a slight stretch to them.

2K7TTMIA

Depends on your road conditions and if you're riding stock or modified suspension. With 8.5 fronts, stock suspension, good to moderate roads, IMO, 245/35/19 fronts, 305/30/19 rears on the 19 X 12's. YMMV. GL.

morganabowen

I also have 19s on my C4. The fronts are 235x35x19s and the rears are 285x30x19. I tried to get 305s on the rear but they just wouldn't fit. Now that I have the car lowered with coilovers, I might try again or maybe go to 18s with a wider rear tire

malem

i have a 2003 996 TT so the AWD is a concern, road conditions are not the best

trisgale

I have your rim sizes and run 235/35 and 315/25

with a 65mm offset in the rear i'm assuming you have stock 17mm spacers for a turbo?

82_930

I also have a C4... go to tirerack.com, they have a tire size calculator on there

82_930

I have 235/35/19 and 275/30/19... this is the recommended size for a C4 with 19"s, don't take a chance with your front diff!

insite

anyone know the allowable difference in diameter between front & rear on the C4?

SSST

You don't want to put 275's on the back of a turbo. Check down on the 996 Turbo forum and see what some of those guys are running. I looked into 19's a while back and there were just too many variables to contend with. Also, if your roads are bad, 19's aren't going to improve your situation.

I'm going to 996 GT2 sizing when it's time for new tires. Much wider and slightly taller so it should give me the look I want. The taller sidewal should help a bit with the potholes.

Good luck.

Capt. Obvious

5% difference in diameter is "acceptable" but most people try to stay under 3% to stay on the safe side.

The viscous coupling on these cars is not fragile, it can handle a lot of abuse. A few % difference in tire diamter won't hurt anything.

insite

great information; thx. going to assume it will be similar on my BMW x-drive since i can't get any straight answers from the bmw forums. people here are savvy.

SSST

5% would be about 1.25". That's way too much IMO. Even if the viscous coupling would take it, I'd guess it would probably trigger some wonky PSM behavior.

Capt. Obvious

BMW X-drive (in my opinion) is trash. From speaking with some BMW tech friends, I would actually keep my diameter differences under 2% on an AWD Bimmer.



(I'm kind of an AWD nerd) LOL

insite

My issue is that BMW spec'd a 235/45-19 for the front of my wife's x3. Tire choices in that size are shyte. The oem difference front to rear is .3" (1.15%). I want to step up to a 245/45 front (2.3% delta). Think it will work? Appreciate your opinions.