Miata front subframe reinforcement

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Miata front subframe reinforcement

Post by jeffw » Sun Oct 08, 2017 9:49 pm

The area where the lower control arm mount is welded to the subframe is a weak spot, and more and more subframes are cracking in this area. I believe John and Nate's car cracked there at Pocono, and Julie's car developed a crack there that we caught during regular maintenance. Team Miskoe's Miata had to retire from the last enduro at VIR due to the subframe cracking.

The Miatas we are driving could be up to 28 years old at this point, and a broken subframe is both a safety issue as well as a financial issue. A used subframe is usually over $300 and new is $400+shipping.

In response to this problem, Mazda has produced a pair of subframe reinforcements that are made from 12 gauge laser cut steel and are designed to be welded into place to help alleviate stress cracking at the factory weld on the subframe caused in the harsh racing environment.

The braces weld into place in between the lower control arm mount and the main body of the subframe and have a large dimple die hole in the center of them to help give them strength and also serve as an inspection hole for tech to be able to see the original OEM subframe welds.

These parts are accepted on Spec Miatas in both SCCA and NASA. I would like to request that this be a 0-point modification as there is not a performance gain from this part.

There is a thread on Mazdaracers (the home of the Spec Miata class) at http://mazdaracers.com/topic/6308-subfr ... -scca-nasa with quite a bit more info and comments on the issue.

I would appreciate your feedback on this, and please let me know if you have any questions about this issue.

Cracked Subframe Photos

Uninstalled Part

Installed Part
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Re: Miata front subframe reinforcement

Post by Bobc » Wed Oct 11, 2017 6:50 am

I would be good with 0 points for that it appears it could be a huge safety issue, there is not much left holding the lower a arm on with all the cracks shown in the pictures.

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Re: Miata front subframe reinforcement

Post by WillM » Wed Oct 11, 2017 10:33 am

I bought a set of these for my '95 street car. I can bring them to NHMS or to a BoD meeting, if it helps. They are tiny. Tiny!
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Re: Miata front subframe reinforcement

Post by StephanAlfa » Thu Oct 12, 2017 8:51 am

I agree that re-enforcing sub-frames is a safety issue. For that matter this should NOT be exclusively for Miatas.
If a ruling is going to be passed for having 0 points in re-enforced sub-frames than it should apply for ALL cars, period.

So I propose this be extended to all vehicles in the interest of safety.
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Re: Miata front subframe reinforcement

Post by offcamber09 » Fri Oct 13, 2017 4:20 pm

I'm good with that as 0 points.
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Re: Miata front subframe reinforcement

Post by n1gzd » Tue Nov 27, 2018 1:13 pm

I agree that this should be zero points. It does not change performance but makes the car safer

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Re: Miata front subframe reinforcement

Post by Mick » Wed Nov 28, 2018 12:15 am

E30's have a similar issue. Not sure if this was the intention, but as Stefan mentioned prehaps the rule should be generic (and apply to front and rear) rather than Miata front subframe specific.

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Re: Miata front subframe reinforcement

Post by Dtangard » Wed Nov 28, 2018 8:30 am

Hi Mick,

I agree. This post was from 2017. The rule passed and it was generic for all cars.
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Re: Miata front subframe reinforcement

Post by peejay » Wed Nov 28, 2018 11:05 am

I picked up a pair of these. Now, who has a lift and a welder and wants to host a Miata subframe reinforcement day? :D
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Re: Miata front subframe reinforcement

Post by dtlemoine » Wed Nov 28, 2018 3:17 pm

Folks - quick PSA... This rule proposal was from 2017. The proposal PASSED last year as follows:

Non-Factory Trim bracing or stitch welding, including strut/shock tower brace, and chassis braces (e.g. X-brace or cross-bar)
(0 point assessment)

Weld away those reinforcements!

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