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daytonars4

ST4 Fender Rule Effectiveness?

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daytonars4

I understand that the intent of the fender rule is to limit the cost of builds, but in practice the rule doesn’t seem to make any sense so wondering what others think? Perfectly legal to bring out a well prepared E46 M that can be easily a $50k+ build running 275’s comfortable under the stock panels. Or a Vette which has the same ability. Yet it’s illegal for a $15k e36 to add a $1500 body kit to properly fit 275’s. What’s allowed is flares that leave 275’s on an e36 exposed and obviously cause an aero deficit to an e46 M. So, why bother with a fender rule when all it does is limit the ability to further prepare older more narrow chassis cars? Once again it’s great in theory, but the rule just doesn’t make any sense in the real world. Obviously an e36 can fit 245’s and avoid the negative aero impact of having 275’s stick out, so that’s not my point. Certain short tracks, like a LRP, benefit from a wider tire. So it’s nice to have flexibility based on track. The tire mod already takes into account someone wanting to run wider tires. That should be sufficient without fender rules.

Edited by Guest

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focusedintntions

Add into that the extreme fender modifications the guy that just won at cota has and it’s seems silly that “limiting costs” excise is used when none of the big ticket items are regulated.

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tcdesign
Add into that the extreme fender modifications the guy that just won at cota has and it’s seems silly that “limiting costs” excise is used when none of the big ticket items are regulated.

 

Those are stock fenders with no metal added, just my metal working skills.

 

To the original poster, there are lots of legal fender flares in ST4 for E36 cars, are you referring to the kits that have venting that are not legal?

 

-tony

TC Design

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daytonars4
Add into that the extreme fender modifications the guy that just won at cota has and it’s seems silly that “limiting costs” excise is used when none of the big ticket items are regulated.

 

Those are stock fenders with no metal added, just my metal working skills.

 

To the original poster, there are lots of legal fender flares in ST4 for E36 cars, are you referring to the kits that have venting that are not legal?

 

-tony

TC Design

 

 

We are all familiar with your impressive fender work

 

It's not just venting that makes wider fenders illegal. There is a very limited view of whats legal. It is only allowed to cover the top of the tire as opposed to an e46 having the ability to fully cover a 275, or have a 245 but with a wider track allowing greater stability. While at the same time with the e46 not creating any compromise to aero. I understand the premise of the rule, but it just seems to put the more narrow chassis cars at a disadvantage. If a client walks into your shop today and says "Build me the baddest BMW ST4 car you can." Are you going to suggest an e46 M chassis or a e36 with the limited option bolt on fenders? My guess is even if the fender rule was not there your answer to the previous question would still be the same?

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focusedintntions
Add into that the extreme fender modifications the guy that just won at cota has and it’s seems silly that “limiting costs” excise is used when none of the big ticket items are regulated.

 

Those are stock fenders with no metal added, just my metal working skills.

 

To the original poster, there are lots of legal fender flares in ST4 for E36 cars, are you referring to the kits that have venting that are not legal?

 

-tony

TC Design

 

 

Tony,

I'm well aware of you're amazing metal working skills. But if that kind of work becomes the norm to build a front running car it defeats the point of some of the "cost cutting" measures (looking at you canards) that were implemented. Please correct me if i'm wrong, but I'm fairly certain that the level of craftsmanship you've shown is significantly more than a set of $400 rivet on flairs. That's really my only concern.

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tcdesign

For ST4, I would choose a 4 door E46 chassis if the customers goal was "fastest ST4 BMW" given the current iteration of rules.


The car that won ST4 was actually built as a ST3/EO car, the customer then switched classes this year as there has been more competition in ST4 in Norcal. If you looked there was very little spacer on that car, it could have run stock, just slightly modified fenders and covered the 245's no problem.


I hear both of you and fully agree. The speeds that ST4 cars go, you can have any flare and vent and its not going to make a real difference in the speed of the car. There are so many off the shelf choices, it doesn't make sense some of the limitations that are in the ST4 aero rules. In particular the front air dam/splitter rules. There are $99 air dam/splitters on ebay that fit miata's that work perfect, but are not legal. To make something legal is 4-10x the cost for no speed difference. Same thing with the E46 cars. There are off the shelf air dam splitters that work great, but don't meet the vertical ST4 rule, again to make a part that is compliant, yet not any slower is a multiple of that price.


I have actual data with 4 different bumper/fender combinations on the front of my GTS3/ST3 E36. The difference in speed whether it be down a straight, or in a corner, is less than the difference of being .5mph min speed faster in turn 14 at Thunderhill and your final speed at the end of the straight. I'm a decent driver, holding .5mph consistency in that corner is about my threshold of ability.


-tony

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daytonars4

I have always felt that if rules were made in consultation with respected shops in the community the end result would be better because there would be less of the “that doesn’t make sense” type of rules. Thanks for the feedback :D

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hoki06

I agree with the OP. If a newer, wider car can run wide tires with minimal aero impact in stock form, why not leave the rules open for older cars to do what they need to run the same tires if they so choose? And the argument that you don't "need" to run wide tires is irrelevant, let the racers make that choice themselves (i.e. and E36 is fine on 245s instead of 275s). The tire templates put a limit on tire sizing so leave fender rules open to the racer.

 

For ST4, I would choose a 4 door E46 chassis if the customers goal was "fastest ST4 BMW" given the current iteration of rules.


The car that won ST4 was actually built as a ST3/EO car, the customer then switched classes this year as there has been more competition in ST4 in Norcal. If you looked there was very little spacer on that car, it could have run stock, just slightly modified fenders and covered the 245's no problem.


I hear both of you and fully agree. The speeds that ST4 cars go, you can have any flare and vent and its not going to make a real difference in the speed of the car. There are so many off the shelf choices, it doesn't make sense some of the limitations that are in the ST4 aero rules. In particular the front air dam/splitter rules. There are $99 air dam/splitters on ebay that fit miata's that work perfect, but are not legal. To make something legal is 4-10x the cost for no speed difference. Same thing with the E46 cars. There are off the shelf air dam splitters that work great, but don't meet the vertical ST4 rule, again to make a part that is compliant, yet not any slower is a multiple of that price.


I have actual data with 4 different bumper/fender combinations on the front of my GTS3/ST3 E36. The difference in speed whether it be down a straight, or in a corner, is less than the difference of being .5mph min speed faster in turn 14 at Thunderhill and your final speed at the end of the straight. I'm a decent driver, holding .5mph consistency in that corner is about my threshold of ability.


-tony

 

I 100% agree with you, Tony. I chose an off the shelf, relatively cheap bumper lip to act as an air dam and it worked great. I'm currently making a custom solution so I can meet the vertical +/- 5° rule for TT/ST4. There is a negligible difference in performance but a custom solution is required to meet the rules.

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