Subframe Reinforcement Status Thread

[wahsm]

I DIY'd mine and was involved in another DIY. What I saw was enough to convince me there is no such thing as one of these cars with no subframe mounting cracks. And you won't know until you drop the subframe and grind it down to the bare metal, at which point you might as well weld in the plates. By the time you can see the damage from a visual inspection, it's probably the passenger front which means the driver rear is toast.

Census on the old forum was that welding with foam in place was a fire hazard. Wouldn't do it if you're planning on reinforcing later.

Mine didn’t have cracks. Not all of these cars do do and this was after tracking the car for 2 years. Reinforced anyway since I was replacing all the bushings and upgrading the suspension

[PerformanceEurowerks]

We have reinforced numerous E46s and E36/8 Z3s and highly recommend doing it whether you see a crack or not. As other's have mentioned, you won't really know the full extent of things unless you lower the whole rear assembly and grind down the undercarriage coating.

What is just as important is that you weld with a clean surface and take necessary precautions to minimize any type of inner cavity or external corrosion after the reinforcement. With us being in the Midwest, many of our clients drive their cars all year round. We are often exposed to a lot of salt on the road. So when we reinforce our client cars, we go through extensive measures to minimize the risk of corrosion.

Our general undercarriage sealing consists of the following; weld through primer before/after welding, seam sealer, rubberized coating, paint, and inner cavity sealer.

[clawhamm3r]

I DIY'd mine and was involved in another DIY. What I saw was enough to convince me there is no such thing as one of these cars with no subframe mounting cracks. And you won't know until you drop the subframe and grind it down to the bare metal, at which point you might as well weld in the plates. By the time you can see the damage from a visual inspection, it's probably the passenger front which means the driver rear is toast.

Census on the old forum was that welding with foam in place was a fire hazard. Wouldn't do it if you're planning on reinforcing later.

[liam821]

Mine was visibly cracked without having to drop the subframe, once I did it was even worse under. I ended up having all the cracks welded and fixed, welded plates on, and will do the foam on top. The foam is fairly cheap, easy to do, and works well so why not. My car had 110k miles without any sort of reenforcement done - i brought it broken.

I guess it depends on if you track your car, the type of suspension etc, but I'd have plates welded on and do the foam, but I track my car so I'm probably harder on my car than most.

[eacmen]

Watch the videos online from Reddish. Most of the subframe damage is typically covered by the subframe when its mounted to the vehicle. Once you see cracks without dropping the subframe then it has gotten quite bad.

I would recommend at the very least lowering the subframe enough to see above it.

If you plan to keep the car you need to start budgeting for a real solution. Redish, VinceBar, CMP, Mason all have good solutions with their own pros and cons.

[Stepstools]

Interested to hear something on this as well. The shop that did my PPI back in November said the subframe was clean and I checked personally last week when I had the rear end up for shock mounts and diff bolts. What is recommended for a car with an undamaged subframe that might see some occasional track time in the near future?

[scubastove]

Just picked up my new (to me) 2002 M3. I brought it to my shop (VAC motorsports in Philly) for a subframe analysis. The tech mentioned that since he saw no cracks or any signs of stress to the area, he recommended the foam injection remedy that BMW offered back in the early 2000's. According to him, if the subframe mounting points are in good shape and show no signs of cracking, he stated that he did not want to drop the rear subframe, galvanize the steel and weld in the plates. Mind you this is coming from VAC motorsports, they specialize in these cars and know their stuff.

Has anyone had any experience with the foam injection process for subframe reinforcement? And what have your results like? Eventually I'll wind up reinforcing it, I just want to only have to do it once. Thanks!