OEM Miata Sub Frame Brace for 90 legal in ST4?

[MiataSteve]

The rules allow "bolt-on" frame stiffeners in ST. The factory brace for the early Miatas require welding of tabs onto the sub frame. Is the welding of the tabs allowed within the ST rules?

[WillM]

I do not think that would be legal. You could, however, install the newer subframe. I believe the '93 1.6 was the first year to come with those tabs, but could be wrong.

I believe there are other aftermarket braces that are bolt-on for the earlier chassis, however none of them AFAIK are similar in construction or attachment as the OEM "ladder frame" that I think you are referring to.

[nateh]

I agree that welding tabs on would be illegal.

I don't think replacing the sub-frame is legal either. That's not legal even in SP.

[CP]

There was SCCA talk last year about allowing the NB front subframe to be used in the NA chassis for the better placement of the steering rack allowing for more favorable bumpsteer geometry. It's a bolt-on affair and something to be aware of if you guys are really trying to be strict about rules. You can tell the difference by the round channels inside which the alignment cam bolts reside. The NA channels are welded to the subframe whereas the NB channels are part of the subframe itself. Pretty easy to spot.

[WillM]

I agree that welding tabs on would be illegal.

I don't think replacing the sub-frame is legal either. That's not legal even in SP.

Nate, either you misunderstood my comment or I misunderstand the rule. I believe the '93 Miatas (also a 1.6) came with those tabs on the subframe (but I could be wrong).

If Steve went to the dealer to purchase a replacement, he'd get the new one, as I believe the new part superseded the old.

What do our rules say about that? Manufacturers discontinue & supersede part numbers all of the time. I think there are about 50 part numbers for a 1990-2005 Miata oil pump, for example.

[nateh]

If it's a supercession, then I think it's OK. Thanks for clarifying.