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> SCCA Tire Rules Interpretation
post Nov 1 2017, 07:33 PM
Post #1

Group: Autocrosser
Posts: 3
Joined: 22-January 12
Member No.: 54811

I have an 06 Miata Touring. It has the 16x6.5 inch wide wheels stock. i run CS but would like to go to the more common 17x7 wheels.

Now the SCCA stock rules state that you can go up or down 1" in wheel diameter, but the width has to stay the same.

I have talked to several people that say you can run the size wheel that came on any model of that car in that year. That is, I could run the 17x7 since other models of Miatas came with that size.

I really want to stay in the stock class and don't want to run afoul of the rules. Can anyone point me to any additional info on this rule?
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post Nov 1 2017, 08:10 PM
Post #2

Group: AZ Region Member
Posts: 2395
Joined: 30-November 05
From: Tempe, AZ
Member No.: 532

Generic answer here. Note that I'll go ahead and assume wheels were available from the factory or as a port install, since I'm pretty sure of that for the NC. Dealer installed options are currently not legal.

If the wheels were available as a line item option for your model year, you can run them.

If the wheels were available as part of an option package, you must install the entire option package.

That's the strict interpretation that you would be held to at a national event. At a local event, things are a little more laid back, but if you start beating a lot of people they're going to expect your car to be compliant.

Manfred Reysser
2001 Celica GT - gone to the clearing at the end of the path
2013 FR-S

"As long as my car goes I drive it. I like racing to the limit, first and last." - Gilles Villeneuve
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post Nov 1 2017, 08:13 PM
Post #3

Group: Steering Committee
Posts: 8929
Joined: 6-December 02
From: Glendale AZ
Member No.: 4

You are correct. In SCCA Stock Classing, only diameter can be changed +1/-1. Width may not be changed.

However, *if* there was a different model/package of your car (same year) that came with a wider wheel, you could run that in Stock as long as you turned your car into the complete special package. Every single part or option that came with the wheel package would have to also match.

One model Miata in 1992 came with 6 BBS wheels (Black and Tan I think it was), while all others came with 5 1/2. But then it would have had to have the exact other options.....leather interior, power windows, speakers in the headrests........ like that.

Make sense?

(Darn, Manfred beat me by three minutes).🙄

Scott Meyers
2006 Mazda3S .......(Really just a Miata with four doors and a trunk......and +500#)
Education is important. Race Cars are importanter
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post Nov 2 2017, 05:26 AM
Post #4

Group: AZ Region Member
Posts: 1147
Joined: 14-January 03
From: Prescott, Arizona
Member No.: 36

Having owned a 07 and 09 Miata, let me help.
Comments from those who haven't owned one are well intended.
Please remember that SCCA will have 50 AutoX classes to race in for 2018.
if you run, like it and get a serious mod addiction, there are many classes,to,go,to.

The 06/07 Miata actually interchanged naming conventions.
The 06 Miata Touring is the exact same car as the 07 Miata sport.
It's a stripper.
There were no port installed items on the NC Miata,with the exception of a 2007 model one off of about 100 cars with a "trunk package" for Autocross. Created such a weenie shit storm, it was Never to be repeated by Mazda.

The stripper MX-5 gets the 16x6.5" wheels and a plastic rubber steering wheel.
The next model up 06/sport/07 Touring have 17x7, and a leather wrapped steering wheel and cruise control.
Both had vinyl tops.
The GT models had all that more soundproofing, leather interiors, heated seats, auto dim mirrors and cloth tops.
It's that simple. Looking at online Brochures will verify what I am saying.
The performance variation between the 3 models of the identical car are about zero.

To be absolutely, positively, no doubts 100% compliant per SCCA rules, is as simple as going to a wrecking yard, getting a leather wrapped wheel with the cruise control buttons and 17x7 factory wheels.
No other changes required.
The fact nobody knows or cares should tell you something.

Understand that once you move away from the stripper, more options became available, cruise control, fancy mirror, and the coveted limited slip, crappy bouncy Bilstein shock combo.
Which were still options, and not fitted on every car, Touring or GT.
So even buying one, you have no idea what you get until you look it up in the Mazda database.

BOttom line, unless you run National events and start beating National champions handily with your mad skills, in a 11'year old that is over weight, without a limited slip, you have no worries.
Nobody will protest your car.
Even a Mazda dealer can't tell what your car is or came with, without decoding your VIN with their computer.

My advice, get the common 17x7 wheel, wrap your steering wheel with a wheel skin, if you must, come out and play, and try not to overthink things. The fast guys and gals with the limited slip, $3500.00 shocks in newer cars don't care and aren't scared.
Slow fat guys aren't scared either.

Don't make yourself crazy. Come out and play. Have fun.
If and when you get really serious run National events, you'll be changing cars or borrowing a ride anyways.
My 2 cents.
Now you know.

Harry Berzes
Prescott, Arizona
Golden Dogs Racing
16 Mazda MX5 Jet Black Mica GT
All leather, way too stock. For now.
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post Nov 2 2017, 09:47 AM
Post #5

Group: Autocrosser
Posts: 110
Joined: 23-August 13
From: Tucson
Member No.: 140721

What Harry said.

My well-intended .02:

If you have the wheels already on the car (hence your reason for asking to run them), as others have suggested, come out and try an event, or 2, or 3.

If you DO get serious/blow everyone into the weeds, that's when you should think about *compliance*.

Have fun, welcome to the addiction!


Victor Lim
BS 1999 Corvette FRC
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post Nov 2 2017, 11:24 AM
Post #6

Group: Autocrosser
Posts: 3
Joined: 22-January 12
Member No.: 54811

Thanks for everyone's input!

As I turned faster times last Sunday I realized that I was reaching the limits of my 340 treadwear tires, hence the question. I only want to change the wheel/tire combo once, so I'll definitely look at everyone's info above.
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