paranoidandroid

Hey wheel experts - I've got a C4S with stock twists (18x8 and 18x10), but looking to downsize to 17s for comfort. I see plenty of people have done so, but has anyone ever put the same size wheel/tire combo on all four corners for C4/AWD? Most other manufacturers insist on doing this. What happens when we do this on a C4? Is it better/worse?

Obviously, spacers in the back given the widebody (and clear the brakes), otherwise I'd look silly. Whats the max size in the front? 17x9?

Is this a dumb question? All other AWD cars I've had have always had the same size wheel/tire front and rear. The manufacturer insisted on it.

Quadcammer

the car will handle like crap and look pretty goofy. With a bigger front tire (beyond 235), you'll likely get some rubbing with stock fenders and such.

Bottom line, this is a bad idea. Unless you just use the car to drive to the coffee shop and back, do not do this.

paranoidandroid

Forgot about having to roll fenders in the front. Thanks!

While I do drive to the coffee shop and back, I'd like to get to a slightly more comfortable ride. Its a little too firm for passengers. But I was curious if anyone had ever put the same size on all 4 corners on a 993.

Ponchobroke

Why not just put stock staggered 17’s on with std sized tires? It should take care of the required +/- (4%?) diameter difference.

paranoidandroid

That's certainly an option, but I'm trying to understand what happens when one squares all the wheels on an C4. Most other manufacturers do square them on their AWD cars. Is it the additional grip since the weight of the car is so rear biased? I recall early longhoods had a square set up, but they were RWD not 4WD.

orangecurry

Not sure I understand what you are asking - AWD usually needs the same rolling circumference to work properly. Width isn't important.

If you "square all of the wheels", and obviously that would maintain the circumference, C4 or C2 makes no odds, you'd just have less grip at the back than you do at the moment.

Or do you mean something else?

spikej

Ideally the amount of grip should be proportional to the weight it needs to handle and because of the rear weight bias, there should be more grip in the rear, hence wider tread. A square set up in a 911 would oversteer constantly.

paranoidandroid

Thanks..this does clarify. I knew circumference had to be primary the same but was not sure if width had to be. Sounds like width is negligible in order for the awd system to work, but would only affect grip.

paranoidandroid

Got it, that clarifies.

mike cap

What are you running for tire pressure? General consensus here is around 34 F and 38 R on 18”.

paranoidandroid

34 front and 36 rear.

cgfen

same size tyres?
or
same diameter tyres?
if the latter, just stick within 2.53489% rolling circumference front to back and you'll be fine.

max911

Will 17 inch wheels even fit over the Big Reds on your C4S?
Just curious.....

paranoidandroid

Yeah, the fronts wouldn't be an issue but the rears may need spacers. Cup IIs require a 31mm spacer. I would love a set of 17" Fikse FM10s but have other priorities to address too. Tough decisions.

Gbos1

No No No No and NO ……..