2023 Rule Proposal: Drop subframe connector mod for E36/E46

[ssmith]

Since apparently I feel like fighting uphill battles this week, here goes:

There's a rule in section 5.2 (p7 of ruleset 2022 ST1-4 v16.2) that reads:

Quote

CCR 15.6—Roll cages may be built to provide an unlimited amount of chassis stiffening. Any number of cage mounting points above the minimum required can be used. Any number of additional tubes, including those penetrating the firewall are permitted. Additional tubes converting the vehicle into a tube-frame chassis vehicle are permitted in ST1, ST2, and ST3.

This overrides the CCR rule 15.6.2 (p44 / pdf p56 of 2022.2.1 CCR) that would normally restrict chassis stiffening:

Quote

Chassis stiffening is a side benefit of a good roll cage system, but it is not the intent of these rules. Parts of the cage deemed by the Chief Scrutineer to serve no practical purpose other than chassis stiffening may be considered in violation of the intent of these rules.

So stiffening any other part of the car is normally considered acceptable, including shock towers or other suspension mounting points, but for some reason stiffening the rear subframe of some cars yields a penalty while for other cars it does not.  Super Touring has a rule in Appendix A (p27 of ruleset 2022 ST1-4 v16.2) that reads:

Quote

Ford Mustang and BMW E-36 and E-46 M3:
"Upper sub-frame connectors" that penetrate and modify the floor pan will be assessed a -0.2 Modification Factor (seen commonly in American Iron Mustangs).

Ignoring the wording on whether this applies to all E36 but only E46 M3, or whether it only applies to E36 M3 and E46 M3, I would like to propose that this be eliminated for all BMWs.  I can't speak for Mustangs as I do not understand the details of that chassis.

In my opinion, this hinges on two issues:

1. Is there a performance advantage?  I don't believe there is.  Some of the fastest cars in ST4 Norcal and ST4/TT4 Champs do not take the penalty: Cars #38 and #3 do not take the modifier yet #38 easily won TT4 at Champs and both were the two fastest cars in the Sunday Champs race.

2. Is it equivalent (or a step) to building a tube frame car?  After all section 6.1.7 (p9 of ruleset 2022 ST1-4 v16.2) states:

Quote

If a vehicle cannot be driven safely, at full speed, with any of the added tubes removed, it is considered a tube-frame chassis conversion.

I don't believe this is a good application of the tube frame rule.  A chassis that isn't broken does not need the subframe connectors in order to drive safely at full speed.  Instead, the subframe connectors are one way to keep the chassis from tearing apart over the course of seasons.  Another choice might be to remove the subframe and fuel tank each season and reweld a new floor pan or weld up any cracks that start forming.  However that would be considerably more expensive.

 

So in the end adding subframe connectors is really just a cost savings issue, not a performance issue, doesn't make the car a tube frame car, and is allowed by the ST rules in order to stiffen the chassis.

[int2str]

I second this motion.

Though I'm weirdly offended by the characterization of the TT4 win as having been "easy" ?

Btw. the #38 crashed at Sonoma a month before nationals because a rear control arm mount failed (ripped out of the chassis). So I fully agree with Scott here that the E46's really need the sub-frame connector to stay safe.

Hope Greg can reconsider this part of the rules.

[ssmith]

45 minutes ago, int2str said:

Though I'm weirdly offended by the characterization of the TT4 win as having been "easy" ?

I meant "easily won" as in the margin of victory was quite high, looks like it was over 0.6s for both the 1st and 2nd best laps.

[tcdesign]

On 10/26/2022 at 1:10 PM, int2str said:

I second this motion.

Though I'm weirdly offended by the characterization of the TT4 win as having been "easy" ?

Btw. the #38 crashed at Sonoma a month before nationals because a rear control arm mount failed (ripped out of the chassis). So I fully agree with Scott here that the E46's really need the sub-frame connector to stay safe.

Hope Greg can reconsider this part of the rules.

I am also for this rule, but the rear trailing arm pockets and the rear subframe tie-in are not related.  The pocket issue is a separate issue and should have been caught with a pre-race check-over/nut and bolt.

[int2str]

10 minutes ago, tcdesign said:

I am also for this rule, but the rear trailing arm pockets and the rear subframe tie-in are not related.  The pocket issue is a separate issue and should have been caught with a pre-race check-over/nut and bolt.

Yupp, understood. Simply pointing out that the E46's have various known fatique points in the back and thus penalizing this chassis specifically is a safety concern.

[Greg G.]

FYI, the chassis is not specifically penalized.  On the contrary, the rule permits something that is otherwise not permitted at all--penetration of the floor pan--just for these few vehicles.  The rule was added because these specific car models commonly had these mods for not only safety as Scott states, but also for additional chassis stiffening, but there was no desire to open up the floor pans to production vehicles.  There are wider implications to opening this rule up to everyone, without a Mod Factor.  But, we will discuss it.

[ssmith]

So if the bars were under 0.75" diameter, then they would be legal under 6.2.1 1a (holes legal for purposes other than lightening?)

Or if a cage bar went up to the floor pan but not through it, and then there was another cage bar on the other side?

I guess I'm not sure how to balance "cages may be built to have an unlimited amount of chassis stiffening" against the need to retain an unmodified unibody, strut/shock tower, and floor pan.  Isn't the cage itself a modification?  If the intersection of the cage and chassis is allowed (after all how else can you have a roll cage) then it shouldn't matter if it penetrates it or just abuts it, right?  So long as penetrating the floor / unibody / etc doesn't relocate any other part of the floor / unibody.  Otherwise, are cage bars that go from the cockpit to the strut tower even legal, since they have to penetrate the unibody?  Or is that considered the firewall, not unibody?

[Greg G.]

On 11/3/2022 at 8:22 PM, ssmith said:

So if the bars were under 0.75" diameter, then they would be legal under 6.2.1 1a (holes legal for purposes other than lightening?)

Or if a cage bar went up to the floor pan but not through it, and then there was another cage bar on the other side?

I guess I'm not sure how to balance "cages may be built to have an unlimited amount of chassis stiffening" against the need to retain an unmodified unibody, strut/shock tower, and floor pan.  Isn't the cage itself a modification?  If the intersection of the cage and chassis is allowed (after all how else can you have a roll cage) then it shouldn't matter if it penetrates it or just abuts it, right?  So long as penetrating the floor / unibody / etc doesn't relocate any other part of the floor / unibody.  Otherwise, are cage bars that go from the cockpit to the strut tower even legal, since they have to penetrate the unibody?  Or is that considered the firewall, not unibody?

No. There is a more specific rule that applies than 1a) above.  There is no such thing as a "cage bar" on the other side of the floor. 

6c) Floor pans may have maximum diameter 0.75” (3/4 inch) holes drilled into them for
purposes of the attachment of ancillary parts, safety gear, seats, and for the passage of suspension
components.

There is a specific rule regarding subframe connectors through the floor, and they are not "ancillary parts":

6d) Floor pan modifications to include items such as sub-frame connectors, atypical roll cage
bracing, or alternate fuel cell placement may be approved on a case-by-case basis by the National
ST Director, or included in Appendix A, and are subject to possible Modification Factor
assessments.

The cage rule in ST is written that way specifically because the CCR says the opposite, and we decided a long time ago that we wanted people to build the best and strongest cages they wanted to, above and beyond what the CCR requires.

Yes, that is considered penetrating the firewall.

 

Looks like your battle is getting steeper and steeper. ? I said it would be discussed. 

[Emag]

On 11/3/2022 at 10:30 PM, Greg G. said:

FYI, the chassis is not specifically penalized.  On the contrary, the rule permits something that is otherwise not permitted at all--penetration of the floor pan--just for these few vehicles.  The rule was added because these specific car models commonly had these mods for not only safety as Scott states, but also for additional chassis stiffening, but there was no desire to open up the floor pans to production vehicles.  There are wider implications to opening this rule up to everyone, without a Mod Factor.  But, we will discuss it.

As stated in your 2023 discussion thread, every year that goes by makes these chassis more and more obsolete compared to the competition.  I wish we had a datapoint to argue that these modifications do not improve performance, but all we have is the fact that these cars have been running side by side, some with and some without reinforcement, with no perceivable advantage.  
 

The disadvantage is clear though, when we compete against newer, purpose built sports cars that do not require any reinforcements for safety and reliability purposes.  The disadvantage becomes even more clear when one of these chassis tears at the floor seam.  

Edited November 17, 2022 by Emag

[ssmith]

5 minutes ago, CTSVR said:

I have to say with all the calls to change the 305 to a 315, I would rather just not have the rule at all at that point. 
 

Also can we bring back the 4 door/wagon mod factor for ST1-3? I’m unaware of a single sedan that is currently competitive at a national level. 

This thread is about subframe connectors, not tire size or sedans.  Please start your own thread for sedans.  It helps keep the pro/con arguments located in one place and thus easy to find.

[CTSVR]

20 hours ago, ssmith said:

This thread is about subframe connectors, not tire size or sedans.  Please start your own thread for sedans.  It helps keep the pro/con arguments located in one place and thus easy to find.

Sorry, got mixed up on the different threads, was using my phone yesterday. 

[Greg G.]

On 11/17/2022 at 8:24 AM, Emag said:

As stated in your 2023 discussion thread, every year that goes by makes these chassis more and more obsolete compared to the competition.  I wish we had a datapoint to argue that these modifications do not improve performance, but all we have is the fact that these cars have been running side by side, some with and some without reinforcement, with no perceivable advantage.  
 

The disadvantage is clear though, when we compete against newer, purpose built sports cars that do not require any reinforcements for safety and reliability purposes.  The disadvantage becomes even more clear when one of these chassis tears at the floor seam.  

"...all we have is the fact that these cars have been running side by side, some with and some without reinforcement, with no perceivable advantage."

Eric, but under the rules they are not running side by side equally.  The one's with the mod have the -0.2 Mod Factor.  So, if there is no perceivable advantage, then the Mod Factor is perfect? 

[int2str]

5 hours ago, Greg G. said:

Eric, but under the rules they are not running side by side equally.  The one's with the mod have the -0.2 Mod Factor.  So, if there is no perceivable advantage, then the Mod Factor is perfect? 

Greg, I do think we have some "data" (I use that term very loosely here). The two fastest (lap time) cars in ST4 did NOT have the sub-frame connector.
I'm in the unique position that I've now won TT4 in an E46 WITHOUT the sub-frame bracing and having built one WITH the sub-frame connector.

Every cage builder I've talked to, basically insists that the connector is an important safety feature to keep the E46 from fatiguing. Yet, the mod factor seems prohibitive enough to penalize those who do. In other words, drivers/builders are encouraged NOT to do the sub-frame tie-in, despite what the cage builders say.

You're correct in pointing out that the E46 already gets special compensation for allowing this at all, but I think 0.2 makes this less competitive and incentives people to potentially not do it. I would love to see the mod factor be reduced to 0.1 at least, or if you're feeling super generous, make it allowable without a mod factor on the E46

Edited November 19, 2022 by int2str

[Emag]

On 11/19/2022 at 5:43 AM, Greg G. said:

"...all we have is the fact that these cars have been running side by side, some with and some without reinforcement, with no perceivable advantage."

Eric, but under the rules they are not running side by side equally.  The one's with the mod have the -0.2 Mod Factor.  So, if there is no perceivable advantage, then the Mod Factor is perfect? 

This was more in reference to GTS 2 and 3 where there is no modification factor.  Seemingly the largest groups of E36s and E46s racing side by side over the past two decades.  

Edited November 21, 2022 by Emag

[Greg G.]

Hey, Christmas is coming early!   ?

 

"Roll cage tubing may pass through the floor pan for purposes of chassis stiffening and/ or to tie into the sub-frame."

[ssmith]

@Greg G. Thanks! Much appreciated!

[Digitalwave]

Maybe that should be clarified to allow connecting to the REAR subframe?

[Greg G.]

2 hours ago, Digitalwave said:

Maybe that should be clarified to allow connecting to the REAR subframe?

Nope.  No differentiation if the rule is followed.

[mslevin]

Awesome

[int2str]

On 11/23/2022 at 4:16 AM, Greg G. said:

Hey, Christmas is coming early!   ?

 

"Roll cage tubing may pass through the floor pan for purposes of chassis stiffening and/ or to tie into the sub-frame."

 

Thank you, Greg!!!
Merry x-mas!