2009 TT Rules and Car Classification Forms

[Joshua]

For instance, does Grant's tube near the lower left of this photo that connects the passenger door bar to the stock rocker sill take +2 points per 2) above? This tube certainly does not fit the description of 1), and may or may not fit the description of 2), depending on what 2) is trying to accomplish.

Mark

I think your interpretation is correct. Grant's cage fabricator did things a bit differently than I'm used to seeing on Miatas, including the atypical attachment of the door bar to the sill with a plate. It's also unusual to put the main hoop plate on the bulkhead, and to angle the forward tubes to the center tunnel under the dash.

 

I'm liking the F20C though - what class are you targeting?

[TurboShortBus]

It's also unusual to ... angle the forward tubes to the center tunnel under the dash.

That's how I'm planning to construct the front of my cage. It takes advantage of the 7th/8th attachment points (allowed per the CCR) that must mount to either the front wheelwells or the firewall, and ties the cage to the unibody at another point. I also plan to have a vertical center windshield bar start at this point and go to the center of the upper windshield crossbar to resist anything really big from entering through the windshield.

 

Mark

[Joshua]

I'd be careful, since attaching to the center tunnel is not the same as attaching to the firewal or front wheel well and triangulating with the center tunnel may be considered in violation of 15.6.2, "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 ...".

 

The vertical center bar is a good idea, and is consistent with 15.6.17 Additional Reinforcement that states

"Any number of additional reinforcing bars are permitted within the structure of the cage...".

[TurboShortBus]

I'd be careful, since attaching to the center tunnel is not the same as attaching to the firewal or front wheel well...

While Grant's plate attaches to both the firewall and the transmission tunnel, the bars themselves attach to the firewall, which is compliant with 15.6.13 while the plate looks to be compliant with 15.6.14:

IMO, may the force be with you if you're trying to argue chassis stiffening vs driver safety. To me, a stiffer cage is a less compliant cage, which leads to...you guessed it...increased driver safety.

 

While the firewall is not a significantly structural area, attaching the roll cage to the unibody at a point above the floorpan can help prevent the cage from shifting laterally or racking in the event of a side impact, which can help to increase driver safety.

 

There might be some elements of an Aussie V8 Supercar or WRC cage that violate 15.6.2, but I have yet to see anything that revolutionary at one of our weekend events.

 

Mark

[TurboShortBus]

Adjustable brake bias? Would an in-car adjustment take any points? If so, could I just remove the knob for TT competition?

The closest I could find for that is this:

29) Non-OEM driver/cockpit adjustable sway bar or suspension settings +4

Based on my interpretation, a driver/cockpit adjustable brake bias adjuster does not fit this description, so the points would not apply. On the other hand, I don't see it listed as a specific freebie either, so...somebody else might have to jump in here if they see it differently than I do.

 

Mark

[kbrew8991]

unlisted and illegal by my reading, though I'd lobby to take +4 under #29 instead of a DQ

[mrc24x]

Adjustable brake bias? Would an in-car adjustment take any points? If so, could I just remove the knob for TT competition?

The closest I could find for that is this:

29) Non-OEM driver/cockpit adjustable sway bar or suspension settings +4

Based on my interpretation, a driver/cockpit adjustable brake bias adjuster does not fit this description, so the points would not apply. On the other hand, I don't see it listed as a specific freebie either, so...somebody else might have to jump in here if they see it differently than I do.

 

Mark

 

 

I see brake bias adjustment falling under free mods:

 

27) Brake lines, brake boosters, and master cylinder modification or replacement.

 

Time to send Greg another email.....

[Greg G.]

We have not d/q'd anyone yet for having a brake bias adjuster, but then again, it has never been formally protested. I would see it as being part of the No-Points brake line mods, but perhaps we should consider adding it to the list of No-Points mods for 2010.

 

In regard to those cage photos, it clearly takes the +2 for the additional attachment points. However, I also noticed the "trunk halo". This is not a part of a standard cage, and has additional attachment points. I would certainly assess it the +3 for "Additional Chassis Stiffening Devices" if I was teching the car.

[Joshua]

I was wondering about the trunk halo too; what is its purpose? I would think that the standard body and chassis plus rear cage section would provide sufficient protection from a rear impact, and would perhaps even function better as a crumple zone than the halo.

[TurboShortBus]

Where is the fuel tank in a Miata? Behind the rear axle, or ahead of it? If behind the axle, then does this rear halo protect the fuel tank or fuel cell somehow? If ahead of the axle, then why was this rear halo constructed?

 

Mark

[jason]

bump drafting

[TurboShortBus]

bump drafting

I DO recall "somebody at the drivers' meeting" saying that bump drafting might be OK in Spec E30 last weekend at RA...right after saying that everybody takes pride in having no contact...lol

 

I think the cage builder might have gotten that idea from dirt modifieds.

 

Mark

[Grant]

Reading the spirit of the rules, it would seem to me that most floorpan modifications are illegal in order to prevent tube framing and other ways of stiffening the chassis. I am correct to assume that floorpan modifications made for no other purpose than to route exhaust would be approved (my car's exhaust exits the motor on the opposite side of where it did stock)?

 

We have not d/q'd anyone yet for having a brake bias adjuster, but then again, it has never been formally protested. I would see it as being part of the No-Points brake line mods, but perhaps we should consider adding it to the list of No-Points mods for 2010.

In terms of actual performance benefit, I would think brake bias control would offer the same results as aftermarket calipers (which can reduce stopping distances by improving brake bias). Admittedly I always disliked the +2 points for aftermarket calipers, since some cars come with some really terrible stock calipers (e.g., C5s) and upgrades are really a durability mod.

 

In regard to those cage photos, it clearly takes the +2 for the additional attachment points. However, I also noticed the "trunk halo". This is not a part of a standard cage, and has additional attachment points. I would certainly assess it the +3 for "Additional Chassis Stiffening Devices" if I was teching the car.

I don't think the trunk halo's attachment points actually stiffen the chassis in torsion, but its moot because I unbolted that bar and probably won't put it back in unless I'm racing wheel-to-wheel.

 

Where is the fuel tank in a Miata? Behind the rear axle, or ahead of it? If behind the axle, then does this rear halo protect the fuel tank or fuel cell somehow? If ahead of the axle, then why was this rear halo constructed?

The fuel tank is in front of the rear axle and inside the cage structure. The builder (Dan @ Racelabz) noted the number of Spec Miatas he's seen come back with the rear frame smashed in, and was hoping the halo might prevent that. I hope I don't get the chance to "test" it. Edited August 20, 2009 by Guest

[Greg G.]

Reading the spirit of the rules, it would seem to me that most floorpan modifications are illegal in order to prevent tube framing and other ways of stiffening the chassis. I am correct to assume that floorpan modifications made for no other purpose than to route exhaust would be approved (my car's exhaust exits the motor on the opposite side of where it did stock)?

And, other floorpan mods are done to re-route exhaust and other under-vehicle parts so that the car can be lowered more than a competitor's similar model to gain a performance advantage. I would not assume that any floorpan modification would be approved at all. Here are some of the rules listed in the PT, TT, and ST Rules. Building a car that is not compliant with the rules, and then asking for a waiver is never the best way to approach competitive motorsports.

 

 

5.2.2 Base Classification Table and Listed Base Weights

Any tube-frame, never street legal, monocoque purpose-built racecar, vehicle not approved by

the DOT, TUV or Japanese government for street use, or production vehicle that does not retain

the original front clip, floorpan, and sub-frame, or is converted (partially or wholly) to a tubeframe

design, that is not otherwise classed below or in Appendix C, will default to the Super

Unlimited class until evaluated by the National PT Director for possible homologation into

another class.

 

6.3.2 Base Classification Table and Listed Base Weights

Any tube-frame, never street legal, monocoque purpose-built racecar, vehicle not approved by

the DOT, TUV or Japanese government for street use, or production vehicle that does not retain

the original front clip, floorpan, and sub-frame, or is converted (partially or wholly) to a tubeframe

design, that is not otherwise classed below or in section 6.2.7 or 6.3.1, will default to the

TTR class until evaluated by the National TT Director for possible homologation into another

class

 

7.3 Vehicle Modification Restrictions/Limitations

Unless listed below or in Section 7.2, any other performance enhancing modifications are

permitted, provided that the vehicle complies at all times with the minimum “Adjusted”

weight/power ratio (7.4) for its class.

1) ST1 and ST2 only (not applicable for STR1 and STR2): Every vehicle must retain its

OEM frame rails (or unibody), strut towers, floorpan, and subframe. Tube-frame

chassis conversion (partial or complete) is not permitted without a waiver from the

National ST Director. Floorpan modifications to include items such as subframe

connectors, roll cage bracing, and fuel cell placement may be approved on a case-bycase

basis by the National ST Director. Such modifications will be subject to approval

and possible modification factor assessments.

[Grant]

Thanks Greg. I'd read the rules and the floorpan on the car is currently stock. I was just searching for ways to gain some ground clearance (I'd like to run it at Spec Miata ride heights). From the looks of it I cannot legally modify the transmission tunnel for the purposes of exhaust routing (under the clause that any unlisted modification is illegal)?

[Greg G.]

Thanks Greg. I'd read the rules and the floorpan on the car is currently stock. I was just searching for ways to gain some ground clearance (I'd like to run it at Spec Miata ride heights). From the looks of it I can legally modify the transmission tunnel for the purposes of exhaust routing?

Whew. I thought that it was already done! Any modification of the floorpan, including the transmission tunnel would require an approval/waiver. If you have a specific request, please send it by e-mail (not PM). Include photos and diagrams of the proposed modification(s) that can be kept as records of what exactly was approved. Thanks.

[Grant]

My bad, I'd meant to type "cannot" since its an unlisted modification, but thanks for the clarification (I suppose I should I have known that the floorpan includes the transmission tunnel).

[Boxer12]

In regard to the dyno, is that 'uncorrected' rwhp? or 'SAE'?

[TurboShortBus]

In regard to the dyno, is that 'uncorrected' rwhp? or 'SAE'?

This is covered in section 6.4.2 of the 2009 TT rules (v 6.1), beginning on page 28:

 

http://www.nasaproracing.com/rules/Time-Trial-Rules.pdf

 

Mark