Affordable subframe to shock tower support brace options (partsshopmax, slrspeed)

[REF84]

Looking for a way to do rear subframe mount reinforcement on my 2004 330i Sedan. I don't know how to weld and rather not rack up a huge bill at a shop having it done.

This thread got me interested in seeing if there were any other options on the market by now: http://www.zhpmafia.com/forums/showthread.php?23381-SME-X-Brace-install-(easy-RACP-reinforcement-ft-the-Pizzaman-himself)


In the US a "e46 subframe brace" google search gives these two options:

https://slrspeed.com/products/e46-rear-floor-subframe-to-shock-tower-brace

https://store.partsshopmax.com/E46STSFB.html

Similar price and cheaper than getting mason engineering or the SME brace shipped to the US.


Not sure if these designs are inferior or similar enough.

I have a 330i with non-folding rear seats. I did the diff bushings and peaked around the subframe and didnt see any big cracks, but I know thats a definitive answer. I don't drive my car too often but I do like to drive it in a sporting manner, but likely won't be seeing the track except maybe once or twice.


What do ya'll think of these?

[REF84]

I just got off the phone with parts shop max, really cool dude. He said the brace was mostly designed to allow for true coilover installation and reinforce the strut towers. He would do the subframe mount reinforcement plates and solid subframe bushings to prevent the movement/tearing of the rear floor. He said he has done the install with 3m panel bond and had good results, so no welding required.

The cost of the solid subframe bushings + reinforcement plates is 320+ shipping, and the panel bond seems to be about $50.

VERY tempted to try this out as this would be easily done at home in the garage.


Edit: I've found some negative reviews of the PSM bushings on here and other forums, maybe not a great idea.


I am thinking of doing the SLRSpeed bar and their solid bushings. But trying to find some reviews. I think I read on this forum somewhere that if your rear floor is in good shape a top side reinforcement + solid bushings is all you need.

[ZHPizza]

I maintain that plates are just bandaids to put over existing cracks and the real reinforcement is in changing the load path. I believe I posted diagrams in another thread.

Stay away from the partsshopmax brace. I had it and it is hot garbage. Made with heavy, soft steel. Includes little bitty bolts to make it easy to install from the top but not strong enough for the forces were putting into it.

The other one looks solid, but I know nothing about it.

There are some good ones in Europe too - I can vouch for SME in particular. Dude is sharp and makes an excellent brace. Really does it all right on the hardware side too.

[Will]

If you reconsider the welding / shop fees for welding, then perhaps you can consider a CMP's new pieces:

Link to his post on NAM3forum. (https://nam3forum.com/forums/forum/main-forum/e46-2001-2006/183365-something-new-from-cmp-auto-engineering)

Like ZHPizza said, changing load paths seem to be the key.

If you still don't want to weld / pay for welding, there was a guy on the old m3forums with the screen name CCE46M3 who came up with another solution for the cracking problems of the e46. His solution used multiple bolts to secure the top and bottom panels of the RACP. I think he's since sold his m3 and is no longer active on the new NAM3forum, maybe there's an archive of his post. Pretty innovative, and cost effective for cars without existing cracks.

[REF84]

Going to hopefully drop my subframe today to inspect for any cracks. The new CMP piece seems similar to the SME weld in brace but about half the price shipped. SME doesnt say you need to weld in plates so that might be a good option. Looks like the welding part is minimal maybe I can find a mobile welder to come in and do it at my home for a couple hundred bucks. I think regardless Ill go solid bushings on the subframe

Im going through the archive of the m3 forum to see if I can find CCE46M3s posts.


Edit: Here is when he reposted on e46fanatics:
https://www.e46fanatics.com/threads/alternate-rear-subframe-repair-method-check-the-top-of-fwd-mounts-and-spot-welds.998275/

[Will]

^ that's it! Nice find. I forgot about e46fanatics.

[REF84]

I have a pesky parking brake cable that is stuck inside my subframe and doesnt want to budge. It's the only thing holding the subframe up right now. I lowered it a bit and took a peak, and there are no major cracks from what I saw.

I'm probably going to end up cutting off the parking brake cable if I cant get it out, its only $15 on FCP euro, and its driving me insane lol.

I went ahead and ordered the CMP rear weld-in brace: https://cmpautoengineering.com/collections/all/products/pre-order-e46-rear-weld-in-beam

It is only 182$ express shipped from AUS to USA right now. And since its welded from the top I should easily be able to find a local welder to do it for me. I'll cut the trunk myself so all the guy has to do it is weld on the bar, the new CMP brace is same height as trunk so dont even have to reweld the trunk floor back on. This probably shouldnt cost much more than $100 from some dude on craigslist or something. So $300-400 for a welded in top support I think is pretty darn good.


As for bottom reinforcements I dont think I'll need much if I do the topside kit. I might do what CCE46M3 did with the front mounts: bore out the hole and install a longer high strength bolt.

Although I am a bit confused about that, how would I replace the stud thats currently in there for the front mounts? Im guessing the idea is that the bolt goes up through to where the seats are and then goes all the way down to the subframe bushing?

@ZHPizza In an e46 thread you mentioned you would recommend a throughbolt, is this something you did?



I'll also be replacing bushings to solid, planning on doing these UHMW ones from condor speed shop (a little bit cheaper than aluminum and supposedly is still solid but with some mild damping characteristics): https://www.condorspeedshop.com/collections/e46-parts/products/e46-solid-rear-subframe-bushings-e46-e46-m3

[t.er]

God speed on those handbrake cables. If your car is from the rust belt like mine is, it could be super seized in the subframe. I think I spent a full 2-3 days getting them out

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[REF84]

Finally dropped the subframe, I had to cut the driver side parking brake cable on both ends, its still stuck in the subframe lol, ill deal with it later...

39451

As for my RACP, I'm no expert, but looks good to me? 195K miles. Must of been a highway cruiser.

Front Driver Side (over exposed photo but didnt see any cracks, ill get a better one) :

39452

Front Passenger Side:

39453

Rear Driver Side (that black line going horizontally is just a smudge I wiped it off):

39454

Rear Passenger Side:

39455



Do ya'll think I'll be good just welding in the top side reinforcement? If there is another place to look for cracks let me know and I can shoot some photos.

[AM1GO]

It’s too late replying but if a cable stuck in the subframe pull it out from the inside and leave the subframe part in. Once you get it out it’s easier to deal with, heating with a torch or some penetrating fluid.


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[REF84]

It’s too late replying but if a cable stuck in the subframe pull it out from the inside and leave the subframe part in. Once you get it out it’s easier to deal with, heating with a torch or some penetrating fluid.


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Posted it in my build thread but I got it out. Dont have a torch (I really need one), had to drill and continue to use penetrating fluid and then chisel a flathead in between the rubber sleeve and the subframe sleeve.

39465


I just ordered an epoxy/rivet vincebar kit. I will be doing that instead of the weld-in options. I tried finding some local welders and the rates I got were ridiculous, basically the "I dont really know if I want to weld inside your garage" price. With the epoxy/rivet kit I can do it fully at home with an epoxy and rivet gun. Slater on here looks like he did the install and Vince released a 3 part video recently on his youtube channel.


I do have some small cracks on the rear left and right front mounts:

39466

39467


Vince said I should be able to stop-drill and spot weld them. (More welding, ugh). He has his vinceskinz kit but he said I cant get one til November because of backorders.

I'll keep asking around. I asked someone on craigslist to do those two cracks for me and he quoted me $500. I don't weld but that sounds ridiculous. The vinceskinz are $500 shipped for that Id rather wait.

[t.er]

Total deja vu moment with my car from the stuck cables to the crack in the same location and the epoxy vincebar haha.

I've never used one but what if you bought a cheap 120V welder from Harbour Freight for those small cracks? Certainly beats $500. Or, maybe there are welder rentals on craigslist

[YoitsTmac]

I too have pondered about the subframe floor for far too long. I personally believe that non-M power and some auto-x is fine with some plates welded in on the bottom and calling it. Does anyone else find the Vince bar seriously expensive for what it is? I think last I asked it was nearly $900 to my door just for the rear mounts. I think it was even here, but it's not a very sophisticated design for what is a few bits of tubed metal welded together. It has a few pieces for aesthetics, but is otherwise a steel bar with some cut steel tube. I know you can say that about anything but you really could recreate it with your second try just measuring carefully.

Someone mentioned a through bolt being better than mounting something on top of the subframe bolts. This is true. I had a long discussion with an engineer about this. I wanted to make something similar to the Vince bar and capitalize on a simple design that's easy to install. When I got an engineer on board, that's when I got the schpeal.

On the other hand, CMP Engineering says that their design transfers to the loads to other parts. It also has gone through multiple revisions. They (he?) actually addressed the concerns of a full bolt through design, and mentioned that he was able to make it thinner and lighter while barely sacrificing rigidity. He also said that his new design isn't the right for most, but more than sufficient for someone who has a supercharged M3.

Honestly, for someone to confidently say they've used less material and still held the same level of added strength, to me that implies someone who genuinely understands how much strength is actually needed for the floor. although a bolt-through would be stronger, CMP seems to have done the math and sees a non-bolt through solution sufficient for sub...say 600hp cars. It's at the right price point and was an insta buy for me.

[REF84]

I too have pondered about the subframe floor for far too long. I personally believe that non-M power and some auto-x is fine with some plates welded in on the bottom and calling it. Does anyone else find the Vince bar seriously expensive for what it is? I think last I asked it was nearly $900 to my door just for the rear mounts. I think it was even here, but it's not a very sophisticated design for what is a few bits of tubed metal welded together. It has a few pieces for aesthetics, but is otherwise a steel bar with some cut steel tube. I know you can say that about anything but you really could recreate it with your second try just measuring carefully.

Someone mentioned a through bolt being better than mounting something on top of the subframe bolts. This is true. I had a long discussion with an engineer about this. I wanted to make something similar to the Vince bar and capitalize on a simple design that's easy to install. When I got an engineer on board, that's when I got the schpeal.

On the other hand, CMP Engineering says that their design transfers to the loads to other parts. It also has gone through multiple revisions. They (he?) actually addressed the concerns of a full bolt through design, and mentioned that he was able to make it thinner and lighter while barely sacrificing rigidity. He also said that his new design isn't the right for most, but more than sufficient for someone who has a supercharged M3.

Honestly, for someone to confidently say they've used less material and still held the same level of added strength, to me that implies someone who genuinely understands how much strength is actually needed for the floor. although a bolt-through would be stronger, CMP seems to have done the math and sees a non-bolt through solution sufficient for sub...say 600hp cars. It's at the right price point and was an insta buy for me.

The Vincebar was $690 for me with the rear mounts, front mounts, and tools needed shipped to me. The Sweden currency is a bit weak right now so that helps. It is a bit expensive I agree but I am factoring in labor cost here. I can do the epoxy kit myself. If I had a weld kit, I’d have to put my car back together, take it to a shop, then they’ll disassemble, prep, weld, reassemble, it’ll probably cost at least $2000.

If I was having it done for me at the shop I would go CMP engineering plates and the new rear top brace. Both Vince and CMP are similar enough in their philosophy and design that I trust both. There is some contention with the front reinforcement design that I’ve seen on some forums but it’s still pretty similar and consistent.

[ZHPizza]

Found where I had posted my info on the subject:

http://www.zhpmafia.com/forums/showthread.php?24302-It-Is-Time