RACP Failure After Plates

[BMWahba]

You should have installed a vince or Cmp Kit when you had everything out and stitch welded. Just double the work now because you have to drop the subframe to do that stuff anyway as far as I know.

[Speed Monkey]

Oh man OP/Dash, that blows. At least you got a good 100k miles out of it since the first round of chassis repairs. Stating the obvious here, the problem lies with the fact that our M car is derived from this...


...a 318i, which everyone can see is far and away from being a sporting car chassis. That 318i indicates it is just a chassis for a common passenger car, albeit one that is priced in the junior luxury car class of vehicles. Hell, even when BMW cooks-up a premium priced ($100,000 dollars+) and dedicated sports car in the form of the Z8, they still choke and can’t get it right; the Z8 suffers from the front shock tower support failing, and it’s symptom is a tweaked shut line between the hood and fenders.


Then again, even a Porsche, a true sports car maker isn’t immune from screwing the pooch. At least we don’t experience this... 🤔 🤬

[r4dr]

You can reinforce parts all you want from the factory, someone will eventually break something. That being said, BMW really could have done more for the RACP issues.

[mrgizmo04]

You should have installed a vince or Cmp Kit when you had everything out and stitch welded. Just double the work now because you have to drop the subframe to do that stuff anyway as far as I know.

If you have plates already, you can do CMP kit from the top, you don't have to drop the subframe again.

[heinzboehmer]

If you have plates already, you can do CMP kit from the top, you don't have to drop the subframe again.

I thought you had to drop the subframe to get the new subframe bolts in?

[liam821]

Doing the plates is a no-brainer, especially if you already have damage down there like I did, but I think you should do the foam injection at the same time.

[Sergmann]

thats a lot of cracks and after a 190k, the metal is pretty much fatigued. you may squeeze a little more life out of that RACP but im sure the cracks will come back. with that kinda, damage, its best to go with a whole new panel IMO

Agreed. The fix you have implemented will hold for a while but will eventually begin to crack again. The welds look good but there is a lot going on in the RACP that cannot be seen from the two accessible surfaces (top and bottom). The metal has fatigued and will crack again. Adding a top bar will help immensely and should be done ASAP. Given the mileage on the car it may not be worth the effort to replace the RACP but keep an eye our for more cracks in the future. The RACP I took out of my car for reference which showed virtually identical signs of cracking both top and bottom. There wasn't much holding it together, especially in the sprig pocket area.

[Dash1]

Have you talked to Cayn from CMP? He is very knowledgeable and accessible and easy to catch in a chat on FB. He might be interested to chat about your case. He also has interesting materials published https://cmpautoengineering.com/pages/technical

I’ll have to contact him. Thanks for the heads up!

[DiscoWagon]

Which shop did the recent welding repairs?

[mrgizmo04]

I thought you had to drop the subframe to get the new subframe bolts in?

The new bolts are longer so they can reach to the top cups. There is a guide included that threads into place where existing bolts are (remove existing bolt, thread the guide in) to help guide the long drill, but that does not require dropping the subframe. You do need to get under the car since that work is done from the bottom.

[heinzboehmer]

The new bolts are longer so they can reach to the top cups. There is a guide included that threads into place where existing bolts are (remove existing bolt, thread the guide in) to help guide the long drill, but that does not require dropping the subframe. You do need to get under the car since that work is done from the bottom.

Oh nice that's really cool. Makes the install much simpler.

[Dash1]

Which shop did the recent welding repairs?

Racewerkz in Burbank, CA. Great folks!

[Dash1]

The new bolts are longer so they can reach to the top cups. There is a guide included that threads into place where existing bolts are (remove existing bolt, thread the guide in) to help guide the long drill, but that does not require dropping the subframe. You do need to get under the car since that work is done from the bottom.

This route sounds very appealing as I wouldn’t want to drop the subframe again!

[Jersey_M3]

The new bolts are longer so they can reach to the top cups. There is a guide included that threads into place where existing bolts are (remove existing bolt, thread the guide in) to help guide the long drill, but that does not require dropping the subframe. You do need to get under the car since that work is done from the bottom.

What are the part # for the new bolts

[DiscoWagon]

Racewerkz in Burbank, CA. Great folks!

Oh nice! They're the ones who did the plates on my car too. Always curious to find new good shops though.