STS rules and clutches?

It's time to put a new clutch in the 7 and since I'm trying to stick to SCCA STS2 I'm trying to figure out what's legal. The quick-summary rules don't mention it (which means any mod isn't allowed) but how far can I go? Is a full-surface clutch still considered stock replacement? Can I lighten the flywheel at all? Or do I have to stick with Mazda OEM only?

I'm not looking for performance as much as safety. I've seen what happens when a parts store special clutch let go in a rotary and I don't want to risk that. I'd much rather have an all-new unit from a trusted Vendor.

flywheel lightening is definitely a no-no. What constitutes an OEM replacement clutch may be more of a grey area.

So if I go with like the Racing Beat Street/Strip clutch, which is still a full-face, organic surface, sprung disc clutch like OEM, am I ok? The pressure plate offers no additional holding power and max RPM's is not increased. It's just a "heavy duty" version of the OEM clutch, at the OEM size (225MM for my year/model). It's also designed to work with the full-weight factory flywheel.

It's gotta be a stock replacement. If it didn't come on the car from the factory, it's no good.

Now, I personally wouldn't have an issue with you running a clutch like you mentioned above, but you would be illegal. Are you planning on going to Nationals or dominating your region?

i think it falls under the part of the rules that talks about friction materials that are allowed to be different composition than oem, but surface area or some other quantifier can't change

I'd have to say that if it doesn't come from mazda, with a mazda part number with your car as the application, it's not a stock clutch... The flywheel can be resurfaced, but needs to stay within factory specs.

No body is going to complain until you start winning. IMHO any stock size clutch mounted on a stock flywheel SHOULD be okay. If your just doing local events I don't think anyone will complain but if your going to Nationals then you better have your ducks in a row.

I know of a nationally-competitive Spec Miata driver who used this part of the SCCA rule: "All cars shall use...the stock OEM pressure plate." He is using an Exedy Stage 2, which uses the exact same cover as OE (same tooling, same material, different finish), but has a stiffer spring and a ductile iron pressure plate (OE is gray iron).

There is no weight savings over OE, but the pressure plate is safer and more durable. The higher clamp load probably gives little or no advantage on a motor with such low torque.

In 2008 NASA, this part is legal. It would be easier to legalize prostitution than change the SCCA ruling.

Kramer wrote: It would be easier to legalize prostitution...

Write those letters!!!

STS and STS2 has no clutch allowances over Stock class rules. Stock class requires an OEM part. No other exceptions.

OEM means it's made by the same part manufacturer that made them for the car manufacturer. No exceptions for this either. This doesn't mean that you need to buy a Mazda clutch. Mazda buys it's clutches from a few different parts manufacturers. Yo need to buy the exact same clutch that Mazda buys.

An OE clutch, sold by the car manufacturer is legal. Just make sure it's actually an OE clutch and not a "replacement" clutch. Mazda sells an OE clutch and a "value line" clutch that might not be legal.

The only way to exploit this rule is to know the history of superseded parts from the OE and choose the best one. Be prepared to defend it against protests.

Exedy (Daikin Clutch) was OE to almost every Mazda, from the 1969 1200, to every MX-5 and Miata, to the R100 and every rotary-engined car.

MNAO (Mazda North American Operations) buys from Exedy for much of their OES clutch kits--value kits included. Nothing is different from a value clutch to the OEM part.

And, unless a clutch rebuilder (or repackager) has "knocked off" the cover in China, almost every aftermarket clutch you can buy will have an Exedy cover. Other than Exedy, most performance covers still have gray iron pressure plates, and some have really cheap belleville springs.

Discs are easy to knock off, so cheap stuff is everywhere. Buyer beware.

I believe the Racing Beat upgraded unit is actually made by Exedy. I'll have to make some phone calls...

Exedy made a lot of different clutches, and some of the "value line" clutches are NOT the same as the OEM '91-'92 clutch. Just because it's an Exedy, does not mean it's legal.

P71 wrote: I believe the Racing Beat upgraded unit is actually made by Exedy. I'll have to make some phone calls...

Racing Beat buys some Exedy Stage 1 and Stage 2 kits. They also have their own discs, that they engineer themselves.

Modernbeat, if you have an Exedy clutch, it's either the same as OE (if Exedy was OE on that particular car), or a performance clutch that will be better than OE. Exedy does not build a cheaper clutch for "value line" kits.

Will they actually remove the inspection plate and check the part numbers at regional or national level?

YaNi wrote: Will they actually remove the inspection plate and check the part numbers at regional or national level?

Don't think so. The way i understand it-

If you are protested, you have to prove it is legal. Guilty before proven innocent. The proof needs to be adequate to satisfy the accuser and the SCCA (has to be legal as per the rules.)