I removed the old RACP plates on my car, here's what I found

[Nate047]

Hey guys,

Long story short, I wanted to share something with the community for posterity's sake.

Here's my build journal with more info about the car if interested: https://nam3forum.com/forums/forum/m...ruin-my-e46-m3

The abbreviated backstory. I bought my car in 2018, it had RACP plates installed as a DIY from the previous owner. He did not document the procedure so I just kind of took his word for it. The plates are BimmerWorld, and the guy installed them using epoxy instead of welding, as recommended by BW. Another note, this car does have a replacement RACP, unsure of the exact age of the replacement panel. But it is without a doubt not the original.

I drove the car for 5 years and about 30k miles, including lots of hard driving and one track day. I'm building the car up and had the rear end off the car anyway, and after seeing the plate job up close in person, I was not thrilled with how things looked and how the plates fit against the body. So after much deliberation, decided to remove the old plates.

To be clear, I did not have an issue with the fact that these were installed with epoxy, in of itself. I do not believe there is an issue with the epoxy method when done properly. It was just how this particular job was performed.

Here is a video showing how the plates looked: https://www.dropbox.com/scl/fi/x7emi...n5zlkhxjv&dl=0

I think it's pretty easy to see why I was not thrilled. It wasn't THAT bad, but since I had all the stuff off anyway, and I have some time, I decided to remove them.

I used a simple wire wheel drill set I bought on amazon to remove the coating around the edges of the plates, then I used a blow torch to heat things up, and a putty knife and a hammer to pry off the old plates. It took me about 2 hours, it was dusty and sucky but not THAT bad. I didn't film or take pictures of the removal part because it was just kind of sucky and I wanted to just get it done.

So... What did I find? Nothing that bad! I did not discover any cracks or damage. Color me surprised TBH.

Here are some pictures and a video.

https://www.dropbox.com/scl/fi/qlei1...qo0yaebml&dl=0

Rear driver's side:

IMG_0265 by Nate Hassler, on Flickr

IMG_0266 by Nate Hassler, on Flickr

IMG_0267 by Nate Hassler, on Flickr

Rear passenger side, this is the side where the plate was sitting away from the body, not flush. Another note, I was running out of time and did very little cleanup here. I used the torch to heat up some leftover epoxy on this side, so that's why the color is weird and it looks probably worse than it is.

IMG_0261 by Nate Hassler, on Flickr

IMG_0264 by Nate Hassler, on Flickr

IMG_0247 by Nate Hassler, on Flickr

Front Passenger side:

IMG_0250 by Nate Hassler, on Flickr

IMG_0249 by Nate Hassler, on Flickr

Does this look normal on the inside? I'm going to ask the welding guy to patch that little spot.

IMG_0257 by Nate Hassler, on Flickr

Front driver's side:

IMG_0253 by Nate Hassler, on Flickr

IMG_0258 by Nate Hassler, on Flickr

IMG_0259 by Nate Hassler, on Flickr

I would be very interested in hearing your opinions on this, obviously the cleanup is not finished yet. But maybe you guys can tell me what you make of this. The scratches you can see are from the putty knife and the wire wheel, they are not cracks. The discoloration is from the blow torch, and some of it is minor rust.

Next steps: continue and complete cleanup of the area, and prep for Redish plates to be welded on. I have a mobile welder coming to do this, as well as the seam along the wheel well. Additionally I will be removing the sound deadening on the top side of the panel, and installing a 6-point rear brace to address top side reinforcement. I should be able to see if there are issues on the top side of the inner panel after I drill and cut with the hole saw, at which point I will address any issues I find with my welding guy. Here is a video showing the interior and some bits about the RACP that seem odd to me.

https://www.dropbox.com/scl/fi/redti...kh3g0ttqo&dl=0

I would really like your guys opinions on this as well, the plan is to remove the mats and this sealer stuff with heat if possible. Then I will prime and spray some simple touchup paint and clear to make it look "okay," or at least "better."

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So what's the final takeaway here? I am glad I did this, I have peace of mind now, and I feel like it's a useful data point for the epoxy method.

I would also say, if you have done the plates yourself and/or have a high degree of confidence in the way the job was done, it's not something I would think twice about. Leave well enough alone.

But again maybe some of you guys with more experience can chime in and give your thoughts on the condition of all this, and wether it surprises anyone or not.

Thanks for looking!

[fattycharged]

Great job so far. Happy to see you didn't have any real issues under those plates and looking forward to seeing the Yurkan 6pt installed since I just ordered one (actually two ) myself. With those results, I'm definitely leaving my epoxied plates alone

[Estoril]

What is the thin black vertical hairline in the 6th photo (just asking).

[Nate047]

What is the thin black vertical hairline in the 6th photo (just asking).

I’m gonna take a closer look and do some more cleanup tomorrow, that may indeed be a crack. But it seems like a weird place for one to form, right? Don’t they usually start around the subframe mount holes and spread out from there? If I discover anything after further cleanup, I’ll have the welding guy repair them.

[Estoril]

I’m gonna take a closer look and do some more cleanup tomorrow, that may indeed be a crack. But it seems like a weird place for one to form, right? Don’t they usually start around the subframe mount holes and spread out from there? If I discover anything after further cleanup, I’ll have the welding guy repair them.

The only way to know to put a probe's fine edge on it and see if it catches and look closely under good lighting.

Best of luck with this project.

[Bry5on]

The engineer in me is cringing that you’re replacing epoxied plates with welded ones for a stiffness and fatigue driven failure mode -_-

[Nate047]

The engineer in me is cringing that you’re replacing epoxied plates with welded ones for a stiffness and fatigue driven failure mode -_-

Did you watch the video and see no issues with how the previous set of plates were fitted? I have no dog in the welding vs epoxy fight. At this point I could go either way on it. I’m just trying to learn and make the smartest decision. It’s hard to navigate the subject because it seems most people recommend welding over epoxy. So maybe you can elaborate on your stance for those of us who are not engineers.

[0-60motorsports]

The engineer in me is cringing that you’re replacing epoxied plates with welded ones for a stiffness and fatigue driven failure mode -_-

I was actually thinking of removing my TMS welded plates and epoxying new Vince or REDISH plates LOL.

[karter16]

Did you watch the video and see no issues with how the previous set of plates were fitted? I have no dog in the welding vs epoxy fight. At this point I could go either way on it. I’m just trying to learn and make the smartest decision. It’s hard to navigate the subject because it seems most people recommend welding over epoxy. So maybe you can elaborate on your stance for those of us who are not engineers.

There's definitely issues with the way those plates have been installed as you show. Also is it just me or had the plates been hammered at?

When I did my plates we made our own, cut/shaped to fit the RACP snugly. The individual components of the plates were welded and then the entire plate for each RACP mount was epoxy bonded with 3M 7333 structural epoxy. The epoxy was confirmed to have spread beyond the edge of the plates around the entire perimeter, then entire thing was then zinc primered, seam-sealed, and the top coated. That was 6 years ago and they look like the day they were installed (obviously from the outside, I can't see underneath the plates, but not concerned as know we had 100% coverage of the epoxy across the surfaces)

In a situation where the sheet metal of the RACP has already been fatigued (and is thin), Spreading the load over the entire surface of the plate seems far better to me than a plate welded around the perimeter and a few spots in the middle. Also an engineer but to be honest selected epoxy approach based on above logic and general knowledge rather than any specific calculation.

[Bry5on]

If it were me, I wouldn’t have bothered to remove the plates like you did unless I saw corrosion near the bondline that concerned me. No harm in doing so and redoing epoxy as a thinner bonded epoxy will generally work better anyway. What you had was likely better than welded plates in my opinion.

Epoxying effectively increases the thickness of material over the entire area where it is bonded, versus a weld which adds bonding at the edges and the pinch point. Think about bending two sheets of paper glued at their edges versus bending cardboard. Not exactly the same thing, since there’s a significant gap in the cardboard which helps, but it is a similar engineering effect. This drives stiffness, which is what the rear subframe lacks.

Additionally, a weld will be 40-60% as strong as the base material that was there before the weld (literally locally weaker than before it was welded). This introduces a nice point for fatigue or cracking to propagate, especially if there is corrosion. Since we’re talking about corrosion, welding through the treated sheet metal is likely to damage the coating on the inside of the subframe, introducing an opportunity for corrosion, even if you cover the visible bottom side really well. Doing the factory foam solution or spraying cavity wax inside after welding could help mitigate this.

Removing welded plates to bond in epoxy plate would be probably the worst possible setup unless the new plates were much larger. I bought my car with welded in plates sadly, so mine will be staying that way.

edit: For clarity, I think welding large plates is a fine solution, especially if they include plug holes. I just believe that epoxy is better in every way. Also I’m just a guy on the internet.

[bmwfnatic]

You made the right choice.

The BW plates are pretty much the worst set of plates available, they are designed without any logic what so ever, because especially on the rear, they end right at the extreme fold where our cars first start to crack, if you were to weld them it would put the already weakest part right into the heat affected zone, and make it brittle and therefore weaker compared to prior.
Their front plates make 0 sense either, front left plate is huge, but front left nearly never cracks, furthermore their provided holes for plug welding don’t line up with the internal structures. like some other plate sets do.

All that leads me to believe other than confirming physical fitment, zero engineering went into their product.

While I think Bry5on makes some excellent points for his case on using epoxy over welding, I disagree to an extent.

An important aspect of welding on the reinforcement plates is drilling holes, both the front and rear mounts have a ‘baseplate’ which is connected to the threads the subframe bolts onto, that baseplate is sitting on inside of the places where we attach our plates to.

The idea is that you use the holes in the plates as guides, and take a drill bit and drill trough the outer layer, until you reach the baseplate, then you start your plug weld on the baseplate, and fill it up, you have now made a 3 way connection consisting of the baseplate, the outer layer and the new reinforcement plate, I don’t think I have to explain why this beneficial, most plate sets call for doing this 2-3 times on all 4 corners.

Now if you were to epoxy a plate set that is meant to be welded, you would be missing out on this extra reinforcement, and therefore I consider epoxying plates that were meant to be welded a bad practice.

However, this isn’t the end of the story.
Because there’s also plates that are meant to be epoxied, like the VinceSkinz, and if you look at the pictures on how to install those, you can see that Vince managed to maintain achieving that multi-layer connection by using rivets over plugwelds, which in my book is a great solution.

So in short: BW plates, regardless of epoxy or weld, hell no…
Epoxying plates meant to be welded, no!
Epoxying plates designed to be epoxied? Sure.

Thanks for reading my rant.

[bmwfnatic]

I was actually thinking of removing my TMS welded plates and epoxying new Vince or REDISH plates LOL.

I did this on my own car, for me it was a good call, as the poor design of the plates put too much heat into already weak zones and the car was cracking again underneath the plates along the outer weld lines, but I welded on Redish style plates with minimal heat, paired with topside reinforcement.

[0-60motorsports]

I did this on my own car, for me it was a good call, as the poor design of the plates put too much heat into already weak zones and the car was cracking again underneath the plates along the outer weld lines, but I welded on Redish style plates with minimal heat, paired with topside reinforcement.

Thats great. when i did mine, car had no cracks at all. I dont know when im going to attempt this but it'll be in the future for sure with the vincebar etc all done one shot.

[ZHLPR]

You made the right choice.

The BW plates are pretty much the worst set of plates available, they are designed without any logic what so ever, because especially on the rear, they end right at the extreme fold where our cars first start to crack, if you were to weld them it would put the already weakest part right into the heat affected zone, and make it brittle and therefore weaker compared to prior.
Their front plates make 0 sense either, front left plate is huge, but front left nearly never cracks, furthermore their provided holes for plug welding don’t line up with the internal structures. like some other plate sets do.

All that leads me to believe other than confirming physical fitment, zero engineering went into their product.

While I think Bry5on makes some excellent points for his case on using epoxy over welding, I disagree to an extent.

An important aspect of welding on the reinforcement plates is drilling holes, both the front and rear mounts have a ‘baseplate’ which is connected to the threads the subframe bolts onto, that baseplate is sitting on inside of the places where we attach our plates to.

The idea is that you use the holes in the plates as guides, and take a drill bit and drill trough the outer layer, until you reach the baseplate, then you start your plug weld on the baseplate, and fill it up, you have now made a 3 way connection consisting of the baseplate, the outer layer and the new reinforcement plate, I don’t think I have to explain why this beneficial, most plate sets call for doing this 2-3 times on all 4 corners.

Now if you were to epoxy a plate set that is meant to be welded, you would be missing out on this extra reinforcement, and therefore I consider epoxying plates that were meant to be welded a bad practice.

However, this isn’t the end of the story.
Because there’s also plates that are meant to be epoxied, like the VinceSkinz, and if you look at the pictures on how to install those, you can see that Vince managed to maintain achieving that multi-layer connection by using rivets over plugwelds, which in my book is a great solution.

So in short: BW plates, regardless of epoxy or weld, hell no…
Epoxying plates meant to be welded, no!
Epoxying plates designed to be epoxied? Sure.

Thanks for reading my rant.

Thanks for ranting. Does this include the "expanded" version, just bought a set:

https://www.bimmerworld.com/About-Us/E46-Rear-Subframe-Floor-Reinforcement-Install/BimmerWorld-E46-Rear-Subframe-Chassis-Reinforcement-Kit_2.html

[bmwfnatic]

Thanks for ranting. Does this include the "expanded" version, just bought a set:

https://www.bimmerworld.com/About-Us/E46-Rear-Subframe-Floor-Reinforcement-Install/BimmerWorld-E46-Rear-Subframe-Chassis-Reinforcement-Kit_2.html

Yeah this stuff is crap, send it back. Get Redish or CMP. You are doing the job anyway, do it right.