SCCA B Street wheel options

[MAG22]

I just want to clarify that the width of the wheel in B Street has to be equal to what was offered OEM, front and rear. Are the any options besides 9" in front and 10" in back? I have a ZCP and I am considering a dedicated track set, and it seems that I am limited to OEM or aftermarket with OEM measurements. I was hoping to go square but it doesn't look like that fits in the rules. Does anyone have suggestions?

[SYT_Shadow]

OEM went up to 9.5 front/10.5 rear optional on the GTS. Does that count?

[MAG22]

CS and GTS are in different classes.

[SYT_Shadow]

Originally Posted by MAG22

CS and GTS are in different classes.

Damn, then you are limited to 9/10

[sholzer]

I didn't think anyone else was crazy enough to run these cars in BS but me =D. But yea we're limited to 9" front and 10" rear tires. The best options I found are OEM 513s or what I have, Apex SM-10s in 18x9/10 with 285/30/18 square. You could go custom too if you really wanted. Photos of the setup here https://f80.bimmerpost.com/forums/sh...&postcount=480

[MAG22]

That is super helpful! Thank you! I’ve been looking out for 513s but the used prices seem to be ridiculous.

And, dumb question, why is it crazy to run these cars in BS? Just because we have some difficult competitors? For me, it’s what I have and it’s a chance for me to push it to its limits. I’m not looking to win, just wanna have fun on the edge.

[sholzer]

Originally Posted by MAG22

That is super helpful! Thank you! I’ve been looking out for 513s but the used prices seem to be ridiculous.

And, dumb question, why is it crazy to run these cars in BS? Just because we have some difficult competitors? For me, it’s what I have and it’s a chance for me to push it to its limits. I’m not looking to win, just wanna have fun on the edge.

They're just not considered to be the best car for the class so you don't see a lot of them, especially at national events. I'm doing at least a few more this year, not sure if I'll make it to Nationals, but I know another guy Rad has been running his down in FL as well.

[Theruleslawyer]

Originally Posted by sholzer

They're just not considered to be the best car for the class so you don't see a lot of them, especially at national events. I'm doing at least a few more this year, not sure if I'll make it to Nationals, but I know another guy Rad has been running his down in FL as well.

I always wonder why they don't just do handicapping so popular enthusiast cars can all be competitive. Like take the national winner and add 50lbs ballast. Granted not every car ever produced could be competitive, but it would even out the most popular options.

[Fosil Racer]

Originally Posted by MAG22

I just want to clarify that the width of the wheel in B Street has to be equal to what was offered OEM, front and rear. Are the any options besides 9" in front and 10" in back? I have a ZCP and I am considering a dedicated track set, and it seems that I am limited to OEM or aftermarket with OEM measurements. I was hoping to go square but it doesn't look like that fits in the rules. Does anyone have suggestions?

First I am new to the forum, so excuse the late entry into the discussion. I am Currently Running a 2015 M4 in SCCA Solo AutoCross. According to the SCCA Rules of 2022 you can use; [Street Category/Authorized Modifications]

"Any type wheel may be used provided it complies with the following:
A. It is the same width as standard and as installed it does not have an off- set more than ±7.00 mm (±0.275”) from a standard wheel for the car. The resultant change in track dimensions is allowed.
B. Wheel (rim) diameter may be increased or decreased 1” from the standard part. This change may be applied to the front, rear, or both axles.
"

The Important part is that it applies to both axels. SO you can run a square set. I have an after market set from TireRack OEM 19" set of Rims and Race tires that work without contest. Also if offered as a dealer option on any M4 it can be used as well.

IN an interesting twist; I also ran a set of OEM staggered sized after market 18" on my 2009 335is. One of my best cornering performances ever was when my mechanic put my rears on my front and Fronts on the back by mistake. So if you are going to Square up, I would use the rear sizes if they clear the front suspension and wheel well. They are wider of the 2.

[Maxnjana]

I also run a 2017 ZCP in BS. This is my first season with it so I'm still exploring the limits and capability of the car.

I found a relatively cheap set of 437s that I put Falken 660s on to run this season. 265 front, 275 rear. I could't find a better combination than this. Maybe someone has found a better size combo for stock 19" wheels?

"Any type wheel may be used provided it complies with the following:
A. It is the same width as standard and as installed it does not have an off- set more than ±7.00 mm (±0.275”) from a standard wheel for the car. The resultant change in track dimensions is allowed.
B. Wheel (rim) diameter may be increased or decreased 1” from the standard part. This change may be applied to the front, rear, or both axles.
"

The Important part is that it applies to both axels. SO you can run a square set.

I find this statement interesting. Has the square setup been verified for legal use in street classes? I have not heard of this before. My understanding of the rule was that you were limited to the wheel width that originally came on the car at each axle position. If allowed to run rear wheel width on front, that's big.

[MAG22]

Well, this is interesting. I can't wait to hear people chime in on this because, I agree, this is big.

[Lappy]

Originally Posted by Fosil Racer

First I am new to the forum, so excuse the late entry into the discussion. I am Currently Running a 2015 M4 in SCCA Solo AutoCross. According to the SCCA Rules of 2022 you can use; [Street Category/Authorized Modifications]

"Any type wheel may be used provided it complies with the following:
A. It is the same width as standard and as installed it does not have an off- set more than ±7.00 mm (±0.275”) from a standard wheel for the car. The resultant change in track dimensions is allowed.
B. Wheel (rim) diameter may be increased or decreased 1” from the standard part. This change may be applied to the front, rear, or both axles.
"

The Important part is that it applies to both axels. SO you can run a square set. I have an after market set from TireRack OEM 19" set of Rims and Race tires that work without contest. Also if offered as a dealer option on any M4 it can be used as well.

IN an interesting twist; I also ran a set of OEM staggered sized after market 18" on my 2009 335is. One of my best cornering performances ever was when my mechanic put my rears on my front and Fronts on the back by mistake. So if you are going to Square up, I would use the rear sizes if they clear the front suspension and wheel well. They are wider of the 2.

You are reading this wrong, diameter can go up or down 1 inch from stock. You can go up or down on any end of the car. Width wise, you cannot change the width at all, running square is not legal as you are changing the front by doing so.

[Theruleslawyer]

Originally Posted by Lappy

You are reading this wrong, diameter can go up or down 1 inch from stock. You can go up or down on any end of the car. Width wise, you cannot change the width at all, running square is not legal as you are changing the front by doing so.

Well you could probably run 275 all around. The wheel width would be different however.

If you want to go nuts, do you have to start from a matched set of wheels? Or can you mix and match any stock sizes? Like if there was a narrower optional wheel, could you run that just on the rear to more closely match wheel widths.

[Lappy]

You can run whatever width tire your heart desires, the wheel width per corner can't change at all. You can however run plus or minus 1 inch on any corner you want. For example I am currently running 19s front 18s rear on my m2, perfectly legal.

[Fosil Racer]

The Rule does not express that the limitation is from axel to axel it says "Any Wheel" that does not offset the Track from the "as Standard..." there is no limit to wheel width if, it came on the standard car. The Track is not altered. And Even if one argues that the rim width changes the track by .25" it is still under the +.275" allowed. It is a tracking dimension limitation not a Rim limitation.

[Fosil Racer]

The question of alternate rim Diameter is answered if the vehicle came with more than one size option for that model. My M4 was standard with both 18" and 19" wheels. So Technically I could go to the smaller rims again in compliance with the 1" rim diameter rule. So a Square 18 or 19 rim set is legal IMHO in BS Class under SCCA 2022 Rules.

[Fosil Racer]

Update: The "Stamped Offset" given on BMW OEM rims for 2015 M4 Front is +29 and Rear is +40 which are in mm. So the rears exceed the front by 11 mm. So the track does change. I assumed they were very close to the same. However that does not effect the width of the rim. So Factory BMW Stock OEM rears not compliant with front under SCCA 2022 Rules. HOWEVER, TIRE RACK has 2 pages of front or rear rims Standard OEM Dimension wheels within the +7.0 mm range. They are with +30 to +36 mm [within the limit] and have rim widths from 8.5 to 10.5 inches. Take your pick and square up, or not.

[Theruleslawyer]

Originally Posted by Fosil Racer

Update: The "Stamped Offset" given on BMW OEM rims for 2015 M4 Front is +29 and Rear is +40 which are in mm. So the rears exceed the front by 11 mm. So the track does change. I assumed they were very close to the same. However that does not effect the width of the rim. So Factory BMW Stock OEM rears not compliant with front under SCCA 2022 Rules. HOWEVER, TIRE RACK has 2 pages of front or rear rims Standard OEM Dimension wheels within the +7.0 mm range. They are with +30 to +36 mm [within the limit] and have rim widths from 8.5 to 10.5 inches. Take your pick and square up, or not.

I think one import rule that is missing is that you must upgrade any option as a whole. You can't do parts. So if you wanted the seats out of a ZCP you would have to completely install the option. IE whatever you start from for allowed modifications must be a package you could have actually ordered a car with. That alone disallowed a lot of option part hijinks. Plus it must be factory installed AFAIK, no port or dealer installed stuff.

[Fosil Racer]

In the case of this discussion about wheels, it is clear that the first part of the Rule says "Any Wheel... A. It is the same width as standard and as installed it does not have an off- set more than ±7.00 mm (±0.275”) from a standard wheel for the car. " Therefore, it applies to any wheel option for the car model [in this case limited to the M4 base not the CS[AS] or GTS[SS]] in the BS class. 18" was Standard and 19" were optional from the factory. So both apply.

[Fosil Racer]

While I agree with your basic premise of staying within the options, you can do parts from different models without the whole upgrade. This was compromised in 2020 when the 2020 Camaro 1LE package and some of the ZLI packages were offered on the SS. I protested this at a race as was in formed by the rule committee that since it was an option listed by Chevrolet for that model it was a legal option for a BS Camaro SS.

Source of options:
[https://www.chevrolet.com/performanc...rice/exterior]

They could install the ZL1 Spoiler on the SS Camaro and it stayed in BS Class that year.

The devil [and compliance] is in the Details. It is also interesting to note that all the Camaros from that genre have now been moved to SS and AS.

[Theruleslawyer]

Originally Posted by Fosil Racer

While I agree with your basic premise of staying within the options, you can do parts from different models without the whole upgrade. This was compromised in 2020 when the 2020 Camaro 1LE package and some of the ZLI packages were offered on the SS. I protested this at a race as was in formed by the rule committee that since it was an option listed by Chevrolet for that model it was a legal option for a BS Camaro SS.

Source of options:
[https://www.chevrolet.com/performanc...rice/exterior]

They could install the ZL1 Spoiler on the SS Camaro and it stayed in BS Class that year.

The devil [and compliance] is in the Details. It is also interesting to note that all the Camaros from that genre have now been moved to SS and AS.

Right, but only because it was an option on it's own. If it wasn't orderable like that it would have been disallowed.

In the case of wheels, since I have a ZCP, and the ZCP was only orderable with 19 and 20 inch wheels I would have to start from those sizes, widths and offsets. I could still mount 18" as its part of the allowance, but I couldn't mount 17" even if they would fit, but a base m4 could.

2019 ZCP- 666m, or 437m are your starting points.
2019 base- 513m or 437m are your starting points.
It might be different from year to year what wheel options exist however.

I don't think there are any meaningful differences of wheels you can actually fit over the brakes. You could put 21" on a zcp, but I don't think there are tires in that size you'd want to run.