THSCC Forums

I have read the SCCA rulebook, and I need some clarification about the Street Touring class. Sadly, I still think of the Street Prepared classes as "new" (from when I used to autox a lot in the 80's), and until just now reading the rulebook was not familiar with exactly what the ST classes are about.

I'm looking at mods to the 2003 330i zhp, so tell me if I have this correct. I'm looking at installing some Ground Control coilovers and front camber plates.

1) Is the car able to run STS if I use 7.5" rims and 225 tires?
2) If I want to then add up to 8" rims, 245 tires, and a limited slip differential, then the car will class properly in STX?

Where does the STU class fit in this picture? I must be missing something in the Solo Rulebook.

Finally, I assume most everyone uses Falken RT-615 or Yoko Neova tires in these classes?

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

Your engine displacement kicks you out of STS into STX automatically. STU is where you would go if you had an M3. Many people have used shaved Falken FK-451s instead of the Falken Azenis (a singular word ending in S, there is no Azeni), Kumho MX or Yokohama due to their more favorable sizes. The base compound of the 451 is the same as the Azenis.

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Has no responsibility whatsoever.

Thanks for the reply Wes. I'm confused about the Solo rules examples in that Appendix A part where is says engine displacement up to 3.1 liters for STS? Under STX it says up to 5.1L. Hence, I assumed STS would work?

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

My bad, I forgot that BMW changed their number designations away from the engine displacement.



If you do the 7.5" wheel, you're going to be waaaaay undertired for the 3400 lbs and then you'll be Rodney fodder in STS. I'd think that a LSD and the wider wheel couldn't do anything but help, especially given how the car treated tires at the NCAC.

edit: I've driven a one wheel peel car that has a decent torque curve and carrying 3000 lbs of weight on seven inch wheels in STS. It is *not* all that it's cracked up to be, even when the car came with thin wheels from the factory. When BMW has 8" fronts and 8.5" rears from der Vaterland, that's a hint and a half. In my humble opinion.

_________________
Has no responsibility whatsoever.

The car will be relatively competitive in STX. I don't recommend running the Falken FK451 as they seem to be the old tire to have not the new. Everyone at the top in STX/STU ran the Yoko Neova or the Bridgestone RE01R. If your looking at only autocrossing locally than I imagine the Azenis RT-615 would be plenty of tire to be competitive.

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2010 Honda Fit Sport
Couple of bicycles

Thanks for the replies, and I agree about the STS under-wheel, under-tire. I've been running on these Dunlop SSRs in 225/40 except for the NCAC event, and although they've been "ok", it is clearly not nearly enough tire for 3370lb plus 200lb driver. The idea of getting the suspension well-sorted coupled with an LSD is very enticing, so STX is sounding interesting.

One more dumbo question: I assume STU class just adds unrestricted engine size (N/A motors) but keeps the other rules the same? (i.e. 8" wheels, 245 tires).

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

If you put an LSD in it, is there any electronic diff or traction control that will need to be reprogrammed to handle it properly?


--Donnie

Yep, the car has "DSC" which includes stability and traction control, but I always run with these totally disabled. On the street with DSC active, others have sad it works fine with an LSD installed, but one would think for it to really work "correctly" it might need some programming to account for the formerly missing connection out back. Good point.

_________________
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 sure it's "totally disabled"? Most vehicles still have a nanny mode they'll use if they sense the "right" conditions with the button off. I doubt at that point it would hurt anything for the DSC and the LSD to be fighting, but you never know.


--Donnie

Yep, in a late model BMW you can totally disable the DSC (thankfully). In the non-M E46, this is a two step process. If you just tap the DSC button, it will disable stability control but not traction control. If you press and hold the button for about 3-4 seconds, it disables traction control also. The E90 is the same way. In the M5 it is completely disabled with just one touch.

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

STU adds unrestrictred engine size (N/A motors) and also adds up to a 275 tire and no wheel width restriction.

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2010 Honda Fit Sport
Couple of bicycles

STX would be optimum for sure. as said, you definately want 8" wheels w/ 245s on them. an LSD would also be very nice as well. a proper performance alignment will greatly improve your tire trouble (assuming you have some w/ stock camber/staggar, i dont know first hand)

stock DSC controls yaw and traction via braking and cutting throttle. I don't see how a LSD would interfere with this. DSC would simply not kick in as often because the slip is being mechanically handled.