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PostPosted: Fri Apr 06, 2018 4:49 am 
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Alright, in my continuing quest to determine WTF I should do with my car, I started comparing brakes to the class winning car (Miata). The GCR spec line shows the Mazda Miata 1.6L (90-97) which, i have learned, means it includes both the NA6 and NA8 chassis. Also, as I have learned, the brakes are different sizes between the NA6 and NA8. The brake specification callout is not much help - it simply states "Factor spec @ all 4 wheels."

In order to do my comparison, should I be comparing to the NA8 brakes assuming that everyone upgraded to these for the additional thermal capacity? The GCR has finally confused me here...

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PostPosted: Fri Apr 06, 2018 5:21 am 
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you can use the 90-97 chassis but only the 90-93 1.6 brakes. The original rules were written for the 1.6L cars but i had a 97 tub i wanted to use and since the tub and suspension are all the same, i petitioned for the use of any of the NA tubs. Im sure people were using them way before i asked the rule be changed. In EP you can use the 1.8 brakes on the miata.


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PostPosted: Fri Apr 06, 2018 5:39 am 
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Yup, the FP spec is for the 1.6L car, so everything on it has to be to the spec of the 1.6L car.

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PostPosted: Fri Apr 06, 2018 6:45 am 
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I'll argue that the GCR does not say that. The engine specifications are for the 1.6L, but because the spec line calls out the 1990-1997 chassis and the update/backdate rule and says Factory Spec in the brake column, why couldn't someone use the 1.8 brakes?

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PostPosted: Fri Apr 06, 2018 9:36 am 
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The spec line is, Mazda Miata 1.6L (90-97). In the United States there was never a 1994-1997 1.6 engine car. Don't know when or why the spec line changed from 1990-1993 to 1990-1997, but it did change. I'd say Bill is reading the spec line correctly. That aside, the larger rotors are not required on a 1.6 car. They may not fit with the 1.6 calipers. ???


NA 1.8 (1994-1997)
Front disc brakes = 255 mm
Rear disc brakes = 251 mm

NA 1.6 (1990-1993)
Front disc brakes = 235 mm
Rear disc brakes = 231 mm

EDIT:

Michael, if I'm not reading the spec line correctly, please explain.

C. Specifications The SCCA will publish Production Car Specifications (PCS) each year. The PCS will contain the specifications for each car eligible to compete in the Production Category for that calendar year.

1. Each line of the PCS will list the make, model(s), level of drive train and suspension/steering preparation, along with all other car specific specifications.

2. Cars can be updated or backdated within the specifications for the makes and models listed on the same specification line of the PCS.

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David Dewhurst
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PostPosted: Fri Apr 06, 2018 10:13 am 
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There are several cars where this issue arises.

This is a tribal knowledge deal that bit a friend of mine last year.

The conclusion we came to last year was that you are declaring the year based on the engine. All chassis parts must conform to the spec for that year.

There are those that would argue based on citing 3 or 4 sections of the GCR that one can assemble a series of rule snipets to justify this tribal knowledge.

This is a major frustration with the GCR. Things should be simple. I should not have to assemble snipets of rules from a variety of places to determine one aspect of car building. And to be honest, this is part of what drew me to GT. The GT rules are far from perfect, but they are far simpler than Prod. I'd also assert that the confusing nature of the prod rules helped give rise to the classes that may well someday kill it (STL and STU).

Long story short, the prod rules could use a ground up rewrite if prod is optimize it's ability to attract new blood.

-Kyle


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PostPosted: Fri Apr 06, 2018 10:22 am 
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disquek wrote:
There are several cars where this issue arises.

This is a tribal knowledge deal that bit a friend of mine last year.

The conclusion we came to last year was that you are declaring the year based on the engine. All chassis parts must conform to the spec for that year.

-Kyle


Was the bit is the bite a production car?

Is the "we", you and friend or was the SCCA tech involved?

I sent anviltester aka Michael a message and am interested in his response.

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David Dewhurst
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PostPosted: Fri Apr 06, 2018 4:04 pm 
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anviltester, I've sent you two messages and they continue to be in my out box. Is you in mail message full?

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David Dewhurst
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PostPosted: Fri Apr 06, 2018 4:09 pm 
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The classification is for a -97 1.6L Miata. If there were such a thing as a 1600 1997 Miata you could run whatever brakes it was delivered with, but there isn't, so you can't. Just as clearly you can't run the 1.8L brakes because again the classification is for a 1.6L, not a 1.8L Miata. I think this could only be misunderstood by someone reading it with an eye toward finding reason to run the 1.8 brakes.

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PostPosted: Fri Apr 06, 2018 4:45 pm 
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David i just saw them and thought id reply here. So this is as i was told 2 years ago (maybe 3) when i petitioned for the 94-97 chassis to be included with the 90-93 as i had a 97 chassis that i wanted to build. No one could (or can) argue that the base chassis is the same from 90-97 - all considered NA chassis. With exception of brakes, motor, and diff they are the same (and the 1.8 diff is allowed per the spec line). Here is the tricky part and ive been down this road with other stuff. The spec line says 1.6L and there was only 1 size discs and calipers for the 1.6L cars - even though a 1.6L wasnt offered in 94-97 models but the chassis are allowed. So the phrase in the spec line "factory spec for all 4 wheels" is based on the 1.6L on the same line. Thats my take on it. Is it confusing, a little bit. I personally have run the 1.6 and the 1.8 brakes on the same car (ultimately went to wilwoods on the old gt car because we could). Other than needing a 1 up aggressive pad for the 1.6 calipers for the way i drive, i didnt see any diff in the braking distance between the 2 (im sure people will disagree with me on that but thats just my experience using the same car and variables other than calipers and rotor size). The 1.8 calipers wont fit the smaller 1.6 rotors. I dont think anyone would notice unless you run up front.

There are a bunch of contradictory stuff ive noticed in the prod rules - my latest is the gap between the windshield and the hood. we whack the windshield off as per the rules. also per the rules you are allowed to remove the plastic trim that covers the wipers and base of glass windshield. Again as part of the rules any trim removed may be covered with a solid panel. But last year many people were told this "gap" had to be there. Had 3 stewards look at it and give me 3 diff answers and my letter to the crb was not clarified as they misinterpreted what i was writing about. Ill be at VIR testing some rules that make no competitive advantage whatsoever - just more mis-written stuff not taking into account other contradictory rules in the same section :roll:

I do wish there would at least be 1 person on the crb at these majors races to see/discuss some of the conflicts in the rules as to get them changed/modified to make things clearer to everyone. But thats too simple an idea i guess.


Last edited by anviltester on Sat Apr 07, 2018 5:33 am, edited 1 time in total.

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