Classing Question

[SWatson]

So I'm running a stock E60 M5 right now. If I install wheel spacers (but still have stock suspension, tires, brakes, etc.), I think that moves me into the tuner class based on what I'm reading on the Classes page.
Do I have that right?

Thanks!
-Steve

[etherpool]

Steve,
Just saw your post. I'll get an answer for you on this ASAP.

[SWatson]

Thanks! No rush, it's a mod I'm really thinking about doing, but certainly not in time for the 8/18 session.

[etherpool]

Our classing coordinator just sent me this.

"Well, the class rule says stock size and width. A liberal interpretation would be any offset would be fine. A conservative interpretation would be only stock offset. I think in this case hewing to SCCA's rule of 0.25" offset difference is okay is the right way to go.

So, if the spacers are less than 0.25" or 6mm they would be fine, otherwise it would bump to tuner."

[SWatson]

Thanks! I'm looking at 12mm both front and back or 15mm (rear), so that would put me in tuner when/if I make the change. Thanks again!

[mcoupemindy]

Track width means so very little in autocross, I don't see why this shouldn't be permissible in Showroom regardless of spacer size. We aren't the SCCA and should NOT use their goofy rule set as a basis for anything. Huge spacers add weight and it would probably be more detrimental than the increased track width.

Bob / Phil, I'd ask you to reconsider the statement posted and permit the use of any wheel spacers in conjunction with stock size wheels and tires in Showroom. It's very common these days to use spacers to "flush it up" on a stock setup.

[bobesser]

I understand the concern about not getting too wrapped up in the SCCA way of doing business and I understand that we are encouraging Friendly Competition rather than cut throat. I also note that we strive to keep Showroom class as close to driving the car off the lot as possible. That is why don't allow sway bars or cat-back exhausts. (please note, these are under review for next season) That said, roll stiffness is proportional to the square of track width. The proposed increase (15mm) would increase roll stiffness by about 4%. If we go unlimited spacer size, we could end up with cars with the tires sticking out 4 inches from the fenders (like that really fast MR2). There are a couple other concerns: increasing front track width will impact scrub radius and potentially make the car more twitchy (problem for the driver) and at some level of track width, we should start worrying about vehicle safety as impacts the strength of the lug bolts/nuts holding the wheels on.

Nice looking M5 by the way.

Bob (classing coordinator)

[SWatson]

No worries from my end, I just wanted to understand what impact they would have on my classing.
Now the only danger is that in a different class, it might encourage me to make more mods...

Thanks for the responses!
-Steve