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April '19 ST Rules Revision Highlights

Greg G.

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3 hours ago, KW78 said:

Hi All,

I have read and re-read the rules and the st forum threads today because I am helping with a ST5 build from an existing spec miata.   I just wanted to make a comment about the "Style" of rulemaking here while referencing the quote above.   As I have no history in the class, I have no idea what the intent was, just what the rule says.   A gurney flap is specifically a product to help a wing, so a vertical fence in front of the louver blades of a given vent piece I would not recognize as a separate aero device that was not permitted.  Any good vent design will have this, and louver blades under the hood surface would just be a less open hole in the hood, and not an actual venting device.   My point is applying intent to the written word and spirit to the rule is why lots of people have left lots of kinds of racing.

My ST5 question is this, the floor rule for SM is slightly different than the floor rule for ST5 - both with the intent to allow the larger surround seats.  The miata kit however doesn't pass this part:    "When inspected from the underside, the OEM floor pan must be unmodified."

Has this exception been made somewhere I haven't discovered?  



Hi Kyle,

As I stated above, we have done our best to go away from extremely lengthy and too boring to read rules.  Yes, we could write rules that have specifications listed for every single rule like the Spec classes tend to do.  Our rules would likely jump from 25 pages to 50-75 pages.  So, we do attempt to short hand.  So, when we have rules that limit what can be done, like the case of Aero in ST4-6, and it doesn't state anywhere that you can add a Gurney Flap (which by definition is an air dam actually) in front of a vent on a hood, and we have had the rule in place for four years in ST and prior to that in PT with no obvious abuse of the language, we don't mess with it.  The manufacturers of the vents are the ones calling these "Gurney Flaps" or lips.  So, you call it a "vertical fence", which again, is by definition an Air Dam.  And, whether it gets put on the car separately in front of the vent, or gets attached to the vent hardware itself, does not make a difference--still was never permitted (until now--up to 3/8").

In regard to my first statement regarding length and reading of the entire rules, please see Appendix A.  See, nobody wants to read the entire set of rules.  I get e-mails everyday with drivers telling me their car model, weight, and Max HP(and no other info), and asking my what class they should register for.


Appendix A—Technical Bulletins for Specific Models/Items

Mazda Miata (’90-’05): The driver’s side floor pan may be modified to accommodate larger/taller drivers. All modification shall be contained between the transmission tunnel, driver’s side rocker, rear bulkhead and no more than 24” forward of rear bulkhead. The modification shall not extend below the factory floor stiffener/frame rail. The steel used in the modification shall be no thinner than .060”. All modifications shall be welded in place. This modification shall serve no other purpose other than seating position. A -0.2 Modification Factor will be assessed for this modification.

Once SM decided to change their rules regarding the floor pan, we weren't extremely excited about it, because it is not a modification that we want to see on our ST/TT cars, and in most cases, is absolutely not necessary.  But, we did add this modification for SM's, and applied a small Modification Factor since they are the only vehicles permitted to have it.

Edited by Greg G.
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Hey Greg, 

Wanted to reach out and say thank you for opening up input for the suspension conversion rule discussion. I think a lot of people will appreciate that!

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On 5/25/2019 at 10:06 PM, Greg G. said:

We are taking another look at this, but not sure it will change anything.  Thanks for your input. 


Thank you.  I look forward to hearing the updated rational / ruling.

My overall rational for making this argument, is that clearly any of these cars (944, corvette, or m3) could be made very competitive while still using the factory "spring" location.  But, it would be far cheaper and easier to use a coilover conversion to achieve the same performance level.  I don't see the coilover conversion as a competitive advantage (maybe others disagree), just that it is a cheaper way.

I think the logic here is similar to why you allow multi-adjustable dampers, instead of limiting to fixed rate or single adjustable.  The final peak performance potential of the car is the same regardless, but buying some off the shelf multi-adjustable and then dialing them in is actually cheaper and easier than achieving the same performance by having some custom fixed rate penske shocks made / testing / revalved / repeat...

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On 5/27/2019 at 3:09 AM, Greg G. said:

Jim, we try and be as short and concise as possible in writing rules, as space and the length of a rule set partially determines the likelihood that it will be read.  If we wrote every rule as you demonstrated, it would literally double or triple the physical number of pages in the rules.  So, we do tend to shorthand when we can.  But, we can change this one to commas and an "and" if it is really that confusing. 

And, you are correct that vents by definition don't have lips.  However, once racers and race part manufactures get a hold of a word that isn't explicitly defined for them, "vents" can have lips, air dams, Gurney flaps.  Apparently, this phenomenon is not just limited to racers--there are some the Internet who would argue that chickens have lips too!

Thanks, Greg. I appreciate the thoughtful reply. I also appreciate the difficulty of writing concise rules that can be understood universally. All I can say is it was confusing to me. Would it be accurate to just say, 'No part of the vent or louver may be more than 3/8" above the hood surface'?

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