Cal Club Autocross Forums

I am looking for a set of wheels for my wife's BMW E36 M3-- we are thinking of running it in CS/ SK2. This car comes stock with staggered wheels: 17 x 7.5 in the front and 17 x 8.5 in the back ( 225/245). I want to put a square set of wheels/tires on it (255/40 sounds good) to get rid of (some of) the understeer. I am reading the SCCA rulebook and not sure if I can put a set of the 4 rear wheels all around (all 17 x 8.5), or else get a set of D-force or Kosei wheels (17 x 8.5) and run 255/40 on all four corners. Also, 1995 M3's came with square set from the factory ( 17 x 7.5 - 235/45/17) on all four corners.

Can I run aftermarket wheels in 17 x 8.5 in CS/ SK2?

Can I run 1995 stock setup which was stock for S50 powered cars (94-96), even though the car is 1999?


Thanks,
Max

The wheels have to be the stock sizes installed in the stock positions. They also have to be the sizes that came with the trim level of your car in the model year of your car.

Thanks for the reply! Sounds like I can change tire sizes as long as they fit ( ie put 235 instead of 225 in the front).

Thanks,
Max

I found, like a number of Boxster owners, that running "squared" tires is a pretty good way to go. I can stuff a 245 on the front 7.5" and easily get a 245 on the rear 8.5". It balances the car quite well as a stock option. And then do an alignment based on that. But not many places can mount a 245 on a 7.5" rim.

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I am concerned that the 245 tire will be too wide for 7.5 inch rim, since I have no camber it may flex too much and will defeat the purpose of the grip of the wider tire. I am thinking of putting 235 on 7.5's and keep 245's on 8.5 rim, that's almost square and front sidewall should not flex too much.Does it sound right?


Thanks,
Max

245 on a 7.5" is easy. 275 on a 6" is pushing it!

Eric Clements wrote:245 on a 7.5" is easy. 275 on a 6" is pushing it!

Seriously, 245 on a 7.5 is nothing.

On the other hand, you may or may not benefit from using a wider tire than specified for your wheel width, depending on the type and even the specific model of tire. The DOT-R tires work just fine when you do that, but street tires can behave differently. Their sidewalls do not provide as much support. Grassroots Motorsports and the Tire Rack did a test on an STR class Miata and found that compared to their standard 255 width tire on a 9 inch wide wheel, the same tire with 245 width (and a little shorter sidewall, and a slightly lighter wheel) was substantially faster through the course. That experiment could not narrow down which factor was most responsible for the difference in times, but I would discount the wheel weight. And I don't think the sidewall difference was big enough for the gearing to make that kind of difference.

If we run the Miata on street tires next year, we're wondering if we should stay with the 9" wheels and 225/45 tires ... or go with a thinner lighter wheel tire combo. This would be for track days, not AX. Seems like it would be more fun on light 225 R tires on those 9" wheels ... Miata's like light

245 on a 7.5" is easy. 275 on a 6" is pushing it!

285/30-18 A6s on an 8" rim takes 4 guys and 15 minutes for each tire. And a case of Sam Adams.

Max Likhterman wrote:I am concerned that the 245 tire will be too wide for 7.5 inch rim, since I have no camber it may flex too much and will defeat the purpose of the grip of the wider tire.

Max you'll be fine with that setup as I had the E36 M3 and I put 245/40/17 on the 17x7.5 wheel so you won't have that problem. And currently on my E46 M3 I put 245/40/18 on my 18x8.0 wheel front, 265/35/18 on the 18x8.5 rear.

Thank you everyone for your responses. Sounds like square 245/40 set is the way to go. Even if there are negative effects of running a fatter tire, nothing as bad as understeering heavy e36.
Gio, you ran spacers in the front, right? If yes, what size?

Thanks!
Max

Max Likhterman wrote:Gio, you ran spacers in the front, right? If yes, what size?

On the E36? Yes. Size between 10-15mm. I believe 12mm was just right.
On the E46? No need.

Giovanni Jaramillo wrote:On the E36? Yes. Size between 10-15mm. I believe 12mm was just right.

Careful about stock legality, you can only deviate 1/4" from stock offset (approx 6mm). But if you have wheels with a different offset than stock, you can run whatever spacer you need to get back to the stock offset +- 1/4"

Ok, thanks. Yeah I just read the rules, the wheels are stock so I can offset them only 1/4 which is 5-6mm spacer. That should work with 7.5 inch wheel, 235 fits without spacer, so 245 won't need much.

Thank you for your suggestions. For now running stock wheels, going to find a second set of stock wheels for that.

Max

Ah Max....forgot you're in SK1 (following C-Stock rules). I was actually doing this while in BSP/STU.

Giovanni Jaramillo wrote:Ah Max....forgot you're in SK1 (following C-Stock rules). I was actually doing this while in BSP/STU.

good memory Gio, i'm surprised you can remember back that far.

}:)

Marshall Grice wrote:

Giovanni Jaramillo wrote:Ah Max....forgot you're in SK1 (following C-Stock rules). I was actually doing this while in BSP/STU.

good memory Gio, i'm surprised you can remember back that far.

}:)

Ah...the good ol' days when it was a gentleman's rule that no BSP competitor would run R-Comps Once Tom Berry left for PAX of course. Been a while since I've auto-xed but memory's still there.

Giovanni Jaramillo wrote:Ah Max....forgot you're in SK1 (following C-Stock rules).

C-Stock is SK2.

Leonard Cachola wrote:

Giovanni Jaramillo wrote:Ah Max....forgot you're in SK1 (following C-Stock rules).

C-Stock is SK2.

Ah that's right. So it's no longer in SK1 the BMW M3 (E36). So who or rather what's the top-dog car in SK2?

Giovanni Jaramillo wrote:

Leonard Cachola wrote:

Giovanni Jaramillo wrote:Ah Max....forgot you're in SK1 (following C-Stock rules).

C-Stock is SK2.

Ah that's right. So it's no longer in SK1 the BMW M3 (E36). So who or rather what's the top-dog car in SK2?

PAXs change every year...

Giovanni Jaramillo wrote:

Leonard Cachola wrote:

Giovanni Jaramillo wrote:Ah Max....forgot you're in SK1 (following C-Stock rules).

C-Stock is SK2.

Ah that's right. So it's no longer in SK1 the BMW M3 (E36). So who or rather what's the top-dog car in SK2?

Right now it would seem to be Morgan's Neon ACR. His driving ability could have something to do with that too, though. But Aaron's right, as PAXes change year-to-year, so does the top dog.

Kurt Rahn wrote:

Ah that's right. So it's no longer in SK1 the BMW M3 (E36). So who or rather what's the top-dog car in SK2?

Right now it would seem to be Morgan's Neon ACR. His driving ability could have something to do with that too, though. But Aaron's right, as PAXes change year-to-year, so does the top dog.

Lucky for us in SK2, Morgan isn't planning on running in the class next year, which leaves Jeff Stuart in his RX-8 in C-Stock as potential top target.

Leonard Cachola wrote:

Kurt Rahn wrote:

Ah that's right. So it's no longer in SK1 the BMW M3 (E36). So who or rather what's the top-dog car in SK2?

Right now it would seem to be Morgan's Neon ACR. His driving ability could have something to do with that too, though. But Aaron's right, as PAXes change year-to-year, so does the top dog.

Lucky for us in SK2, Morgan isn't planning on running in the class next year, which leaves Jeff Stuart in his RX-8 in C-Stock as potential top target.

Dang, was just getting used to having Morgan as a sure pick for the team competition. Well at least Jeff is in PSCC, too, and hopefully he can continue the winning ways.