What would you do with a clean subframe at 50k: FOAM or PLATES?

[Tom Day]

Not sure which is the smarter option. I am not an aggressive driver, not a track day bro, so maybe foam makes more sense...?

[COVID-19]

Both.

[lemoose]

Im kind of in the same boat (brand new axle carrier panel with only 20k miles on it since). I think the best solution is to get the Vincebar or a crossbrace. You can supplement either with the structural foam- although it may not be all that necessary

[James31]

You can’t do both. If you use foam that means you can't weld in the future and welding a brace to connect the rear subframe mounts to the chassis rails is the only permanent solution to the subframe cracking issue

[Tbonem3]

Lang or redish plates and cmp topside reinforcement or custom halfcage with racp tied in plus shock towers.

[Obioban]

You can’t do both. If you use foam that means you can't weld in the future and welding a brace to connect the rear subframe mounts to the chassis rails is the only permanent solution to the subframe cracking issue

You can rivet/epoxy after foaming.

[Silbergrau metallic]

I went with the DMG Autosport Subframe brace. My car didn't have any cracks upon inspection, so I went this route and couldn't be happier. You can really notice the increase in stiffness in the back of the car and the workmanship of DMG is second to none. Go to their website and check out the beautiful Welds on their braces, absolutely look like works of art.

[enjoy_m3]

I looked into doing the foaming in addition to my vincebar. It's actually more work than it looks so I opted out of it. It's very thick so it's much easier if you have a pneumatic gun which is a few hundred dollars. You have to drill into certain in the trunk and create a barrier to keep the foam concentrated in the space around the RACP. All this info can be found from reddish motorsport and their youtube videos. You'll have to dig and watch the earlier ones and there's multiple videos explaining how to property inject the structural foam.

As for the plates, Tbones suggestion of welded plates and cmp/vincebar or something similar is recommended. Reddish motorsport has also documented how the RACP fails. I learned the hard way from my car. I bought the car with no visible cracks. Drove the car a few weeks, drove it hard a handful of times and developed cracks, probably also exacerbated with worn bushings. Welded plates only to find out it transfers the stress elsewhere. Starts at the driver side wheel well where the wheel well panel and RACP connect and works it's way to the right. Spot welds will fail and go un-noticed unless you take off the paint and seam sealer. So I, too, recommend welded plates and some reinforcement on the trunk side. Good luck!