THSCC Forums

Car is BMW 330i ZHP (performance package) which comes standard with 8x18 front and 8.5 x 18 rear wheels. I'm curious if it is possible to run in stock class with 8" rims all around (to allow rotation) and still be in stock class? The 2003 330i came with all sorts of wheel width combinations, so I guess my question is whether or not one can run the smaller size wheel in the back and still be in stock class. I suspect the answer is no, at least I know it is no if you wanted to run 8.5" all around, so I was wondering about using the smaller size all around.

Thanks,
Chuck

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Current stable:
2019 BMW M2 Competition slicktop 6MT
2011 BMW M3 sedan slicktop 6MT
2007 BMW 328i wagon (slushbox for now)
1975 CanAm 125MX2

You are correct, the answer is "no."

Scott

Thanks Scott. Sigh...time to order the 8 and 8.5" rims for the auto-x tires now...sure was hoping to be able to rotate the tires without having to dismount/balance them and all. It is my understanding that tire size is free for the most part? The stock tires are 225/40 and 255/35, but I'm planning on running either 225/40 or 245/35 all around.

Chuck

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Current stable:
2019 BMW M2 Competition slicktop 6MT
2011 BMW M3 sedan slicktop 6MT
2007 BMW 328i wagon (slushbox for now)
1975 CanAm 125MX2

Yes you can use whatever size tires you want to as long as they are mounted on the stock or stock size wheels.

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2010 Honda Fit Sport
Couple of bicycles

Thanks...planning on stock sized rims, 8 and 8.5, SSR GT2.

Chuck

_________________
Current stable:
2019 BMW M2 Competition slicktop 6MT
2011 BMW M3 sedan slicktop 6MT
2007 BMW 328i wagon (slushbox for now)
1975 CanAm 125MX2

The rule with rims in stock class follows the same principle as the rest of the things you can/can't do. If you could order, from the factory, an option on your car that had 8" rims all around, then yes you can run those. However, you have to be careful here because if you could only get 8" rims on all four corners with AC, and the stiffer Bling131 sway bar, then you must be sure your car has AC and the Bling 131 sway bar installed.
You should also be able to find the documentation to prove that this was a factory option. In a nutshell, you can only run the car in a configuration that was a factory order option. This does not include "dealer installed" options that might have been added or changed later.

Hope this helps,

Miles

At the local club level, I think it would be helpful to many to have a "stagger elimination rule" of some sorts. Allow the people who have stagger setups from the factory the ability to run the smaller rim size in the rear *and* you could even limit them to running the front size tire all around also (taking away the free tire size choice) -- something to that effect. It would help people run a setup that they can rotate easily to even out tire wear, etc., and perhaps not dramatically change the competition equation. Anyway, just a thought to help with rotation, costs, etc., at the club level.

On the 330i at the National level, I'm sure anyone would rather run 245/35's all around on the 8/8.5" setup rather than 8" all around on 225/40's.

Oh well...thanks for all the replies.

Chuck

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Current stable:
2019 BMW M2 Competition slicktop 6MT
2011 BMW M3 sedan slicktop 6MT
2007 BMW 328i wagon (slushbox for now)
1975 CanAm 125MX2

Chuck, you can get a lot more than a 245 on an 8" rim. We've had 275's on the RX-8 (18x8's all around) and know some people who have mounted 285/30/18's on 8's. If it's a function of rotation, don't let the wheel width fool you.

Rob Carpenter used to put 225's on a 5" rim. - AB

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'14 Toyota Sequoia Platinum 4WD
Super Westerfield Bros - '93 Integra - LeChump Du Jour
STX 93 - Scion FR-S

As is often the case, what seems to be a minor change, can have effects that are not easily anticipated. Running the smaller size tires on all four corners might work better than one would normally think. I know of respected Corvette drivers that have done well at national events that put larger tires up front on purpose, with good results for their setup. I also know of drivers that have put smaller tires on the car than others in their class, also with excellent results, simply because they get heat into them more quickly.

I'm not advocating the technical merits of the above, but simply wanted to point out that when we make changes to cars or attempt to start changing the rules, (even for local club events) the impact of those changes is sometimes very difficult to truly evaluate.

Miles

The other problem with club level rules is if you want to run another club's event, suddenly find that they don't have the same rule and you end up in a much higher prep level class, or someone outside the club comes in with an SCCA class legal car and finds they are at a disadvantage because of a club rule they won't come back. If everyone adheres to the SCCA rule book then there are no problems. Tire rotation on staggered wheel sizes isn't normally an issue especially with sticky tires. Rotate them side to side, flip the tires on the rims 1/2 way thru their life. A RWD car tends to wear the fronts and rears fairly evenly, but if not just replace them in pairs.

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SPIN or WIN!
there's no glory for going slow.

Or you could just buy cheap ass cars like most of us that don't have the fancy wheel stagger options

...I'm just jealous

I agree completely. The best path is the one THSCC has chosen which is to follow the SCCA rules exactly. Just running the same size tires all around on typical stagger setups, especially one like this one with only 1/2" rim width difference can help balance out understeer significantly. Allowing non-stagger setups may actually require a reclassification of some cars which is way too difficult for THSCC to attempt to administer.

I decided to stick exactly with the rules so I don't have to run in street prepared or whatever it would be -- went with some SSR GT2 rims, 8" front, 8.5" rear. I also decided to buy some of Tire Rack's fire sale Dunlop SSR r-compound tires. They aren't nearly the competitive tire the Kumho V710 is, but we can drive to events on these, etc, and they're half the price of the V710's. The other issue is that they are only 225/40 as opposed to 245/35. For R-compound type tires, the SSR's wear very well...already have experience with them both on the track and auto-x in the M5.

As crazy as it sounds, the last event at Sanford last fall was the first THSCC autocross I had driven in since 1984 (when I used to auto-x all the time in the late 70's/early 80's) -- wonder if there are any of the old guys still around from those days?

Regards,
Chuck

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Current stable:
2019 BMW M2 Competition slicktop 6MT
2011 BMW M3 sedan slicktop 6MT
2007 BMW 328i wagon (slushbox for now)
1975 CanAm 125MX2

I guess we almost overlapped. I started autocrossing with THSCC in either late '84 or early '85 (can't recall exactly), running an '84 Trans Am in the then large F Stock class. I was also strongly associated with NCR SCCA back then, and actually ending up chairing their annual autocross at the Fairgrounds Midway area for several years.

I also once autocrossed a '69 Ford Falcon 4-door at the Fairgrounds on snow tyres when the TA was in the shop (as it was repeatedly)... as I recall, the stop box was a real challenge with four wheel drum brakes and no traction. Not that there was a lack of speed coming into it with that 302 v8...

So I guess we just about barely overlapped. Of course, I am just now back with THSCC after a very long break, but I'm back in F Stock with another Trans Am, so in some ways it's almost like I never left.

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Martyn Wheeler
AXing Kit's '05 Mazda 3, #29 HStock
(when The Gonzo Symphonic allows)

Yes some of us are still around from the old days. I used to run a Datusn PL-510 in G stock before there was H stock.

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George Bright Member # 141
One of the youngest of the old farts.
Yes I voted against you joining the club.

Aw snap, no he di-int.

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Has no responsibility whatsoever.