Does anyone know the exact specs of the wheels and tires for the stock ms3 rims on an 08? I want to compare the backspacing and tire size and width so I am 100% sure it will fit.

Also, does anyone have any experience with ASA rims? Quality, Finish, Lifespan, etc..

 

In the first place, don't worry about backspacing. Worry about off-set. It's a much better indicator.
18x7x+52.5mm. 215/45-18"

 

Is that the size of the stock setup?
18x7x+52.5mm. 215/45-18"

So if I get rims that are the same size, I will be able to reuse the stock tires?

What about the TPMS?

 

Also, can anyone post how much the stock rims weigh? I wanna make sure my new metal is the same weight or lighter. Thanks!

 

I've read they were lighter than the RX8's @ roughly 24lbs, but notby much... say, 22-23lbs ea.

And most places these days are set up to handle a TMPS changeover. They have to be.

 

Well the rims I want at 28lbs each, so I figure gaining the extra 3lbs on each corner is worth the style upgrade..

Question.. how does the offset affect the setup? Like, the stock rims are 18x7 with a 52.5mm offset. The rims Im getting are 18x7.5 with a 45mm offset. Does this mean the rims will stick out further than the stockers? If so, how much of a difference is 7.5mm? Or is it the opposite, and the rims will sit closer to the car and cause a potential rubbing problem?

The recommended tire size for the rims Im getting are 215/45-18, which is also the stock tire size. In this case, Ill probably save a few bucks and have the stock tires swapped out to the new rims. Theyll need replacing before the end of the lease anyways, so when it gets close to the end Ill just put the new set of tires back onto the stock rims so Im all setup to give the car back.

I really appreciate all your help guys. Your making a potential headache into a very easy situation to handle.

 

Yes the wheel will stick out a bit further as you would be increasing the backspacing of the wheel to suspension by .295". However, you would also be increasing the width of the wheel by another .25 that will compensate, for a total of .045". (0.25-0.295= -0.045".)

From the front of the wheel however, you will be adding, not subtracting,that difference and the additional width of the new wheel. But it shouldn't be a problem going 1/2" wider and to a+45mm. Ppl do it all the time.

 

I see, now it all makes sense. Is the rim going to protrude any further than the stock rim? Based on the math it sounds like it wont, or maybe just by 1/4" max. Just want to confirm that thats correct. I dont want to drive around a car with the wheels sticking out all far and have it look stupid.

Do you see any problems with re-using the stock tires?

 

No, the stockers should fit.
New wheels in that size and w/that offset will stick out a bit past the OE's, but the difference would be closer to +1/2".

Sorry, I was rushed this morning and didn't really have time to complete my thought.

You have to add the extra 1/4". 1/2"/2=1/4" (the 2 in the equation being the extra 1/4" in front and 1/4" behind.) in wheels width AND add the additional offset (7.5mm) that you are losing from OEto get how far the new wheel will stick out. So the total would be 6.35mm (0.25") +7.5mm (0.295")=13.85mm, or 0.545"... approximately.
Again, I know others that are running wheels/tires of this size, and bigger,on the MS3's and get away with it no problem.

In my own situation, I had the 17" OE's on my 3. OE size: 6.5"x17'x+52.5mm. I'm currently running 7"x17"x+.50, so I added 0.5" of wheel and reduced the offset by 2.5mm. Approximate adjustment is now +0.348" (>1/3") on the outer edge as compared to stock. Not much, but I wanted to save weight as much as possible (or I would've gone w/18"er's) and maintain the OE steering, brakingand suspension geometry. Even w/the extra wheel width the inside geometry only changed by -0.152", not the 0.25" as it would've had I found wheels w/a 52.5mm offset. Hardly negligible from OE's with a wider wheel.

See what I mean?