[Kgolf31]

Originally Posted by Finnegan

I'd see if there was a way to to go with the 9.5". That's going to add about 2/10" more tread width vs. the 9" wheel with that 265/35 tire. A tire mounted on the minimum side of recommended rim sizes isn't going to work as well as mounting the tire on the measured rim size (9.5" in this case).

My thinking these days is that for front wheels, it may be even better to have a .5" wider wheel than the tire's measured rim size. I think that helps manage tread squirm and tire movement, and realizes the full potential of the tire. (Although fitting a 10" wheel on the front is really feasible.) Rear doesn't see the same lateral forces, and measured rim size works there. Stock wheels and tires have a .5" wider than tire measured rim size on the front--I think there's a reason for that.

I hate to keep on derailing from your thread (my apologies)

I completely agree with the 9.5" wheel. I completely forgot about the extra tread that is added with the increase wheel width. Even though I may screw myself over with a SCCA class (even though that may change with the letter I wrote) the car will be MUCH more fun to drive on the track and auto-x with a square set-up and massive camber

I was thinking ET 35 upfront and ET 22 in the rear. Should be enough with extra camber (i'm hopping I don't have to go adjustable control arms in the rear).

Does anyone know if 17" Wheels will fit? The only problem is that I'll be forced to run staggered

Originally Posted by Finnegan

Just to clarify, I wasn't worried about the wheel rubbing, rather it was tires. A 10" ET25, as a wheel, fits just fine!

Let's say we're looking at a 275/35 round shoulder tire like the PSS. On a 9.5" (tire's measured width) wheel, tread width will be about 10". On a 10" wheel, tread width will be about 10.2".

What about a square shouldered tire like an RS-3 in the same size/aspect? On a 9.5" (tire's measured width) wheel, tread width will be about 10.2". On a 10" wheel, tread width will be about 10.4".

Rated M Roadster is running a 10" ET25, with an RS-3 on a lowered car, but is running a good amount of negative camber (-3 rear) to keep it from rubbing. I think there are plans to roll the rear fenders a bit and dial it back. (BTW, I think his set-up looks unbelievably good!)

Contrast Rated M's setup with that of kennyfrc's stock setup that's running a 275/35 PSS on a 10" wheel. Kenny's is on a totally stock setup, no rubbing, no tweaks. (BTW, that's another very good looking setup).

Section width (sidewall meaty part of the tire) is the same on the RS-3 and the PSS. But not tread width. And wheel size and the tire's measured rim size affect the tread width (~2/10" for each .5" rim increment). That's why a PSS works on the 10" wheel pretty easily, whereas a more square shouldered tire might not work without some adjustments (it will work but there is some tweaking to do).

The other thing about the increase of 1" on wheels is that the space on the front wheel well is more generous, relatively speaking, since the rear starts off at 9", and already uses a chunk of real estate. At least that's my read on the amount of available room. So the 1" change is a bigger one, relatively speaking, given the available real estate.

Bottom line, there are a lot of variables involved in fitment, as I've learned on this journey (still learning):

Tire's measured rim size
Wheel width (and impact to tire's measured size)
Offsets
Lowering
Camber (and how camber is achieve, plates vs. shims vs. lowering or a combo)
Perch location

Lots of good information here. I run 265 RS3s in the rear with stock OEM wheels and I rub on the inner plastic wall. I had to add a 5mm spacer (running -1.5* camber)