Subframe reinforcement epoxy/foam method.

Here I will show you how I did the subframe reinforcement using epoxy glue to mount the turner subframe reinforcement plates. And then reinforcing the subframe using the BMW foam method. The good thing about this method is that you can do everything yourself and you don't need to weld your chassis which can cause rust problems later.

In the BMW TIS they only inject structuring foam on the left side. I did the right as well just to be on the safe side.

What you need:
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Turner subframe reinforcement plates
3M Epoxy Glue 08115 x1

BMW TIS download here: e46_subframe_tis.pdf
Cavity foam 83 42 9 410 694 x1
Structuring foam 83 42 0 307 530 (x2 if you want to reinforce the right side as well)

Thinner or similar for cleaning the surface

Applicator gun. One for the Epoxy and one for the foam. I made my own.
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The applicator guns are really expensive and you need two. So I made my own from a regular applicator gun. This can be used with both the epoxy and the foam cartridges. But you can probably borrow the guns from a body shop.





Here I have sanded the plates down using a angle grinder with sanding plate.


Subframe sanded down.


Test fitting the plates.


Apply the epoxy using this type of tool.


Epoxy applied on the car.


And on the plates.


Mount the plates and lightly tighten the bolts. Don't tighten to hard cause you will squeeze out all the epoxy. I think the epoxy needs a layer of 0.5mm-1mm thick layer of epoxy to get max strenght. You should see some epoxy squeezing out evenly around the edge of the plate. Make sure you don't block the small drainage holes with epoxy.


Use your hands with rubber gloves to spread out the epoxy around the edge of the plate. This is how it should look.


Then let it dry for 24hours +. I let it dry for 48hours before I painted the plates with rust protective paint. Finished!


Then it's time for the foam. It's good to have a print of the BMW TIS when doing this.


First drill a hole in the middle between the holes that are alredy there. You can see that I have made cuts in the floor, this is not necessary when doing the foam method. I was going to do the welding, thats why its cut.


Here you can see the hole hiding underneath.


Then remove the sound deadening to find this hole.


If you plan on doing the right side as well you don't need to look for this hole on the right side. It isn't there, I have looked..




Then fill the two holes with cavity foam as explained in the BMW TIS. Make sure you empty out the rest of the can somewhere or else it will explode!


Preheat the structuring foam to about 60C in a water bath.


Wait 10min then inject the structuring foam as explained in the BMW TIS.


After injecting two cartridges of structuring foam into this hole. The foam expands a lot and fills up your subframe. Some foam will protrude out of this hole and the small drainage holes under the car. Inject two cartridges into the right hole also if you want to reinforce that side as well like I did.


Let it dry for 24hours. Car must not be moved during the hardening period.

Good luck!

Thanks, I've been looking forward to this DIY! There's a great debate about the efficacy of this approach going on over here: http://www.m3forum.net/m3forum/showthread.php?t=280165

win

Awesome contribution to the community. Thanks for sharing.

Cheers JeppeJ - I'm interested in the foam injection part at this stage. Thanks for sharing! Once filled and set this will be pretty hard I reckon and should help reduce and even stop further stress.

Great thread. But I would recommend checking to see if your subframe is already cracked before buying that stuff because you might have to end up welding anyway

Was it really necessary to use the Turner plates, too?

Thanks for the write-up. Where did you get the foam? I searched the PN a few places but couldn't find a place to buy it. Did you just go to a dealership?

Originally Posted by aggieE46

Was it really necessary to use the Turner plates, too?

Thanks for the write-up. Where did you get the foam? I searched the PN a few places but couldn't find a place to buy it. Did you just go to a dealership?

That would save sooooooooooooooooo much time.

AWESOME alternative. Now we just need to find a good way to apply the foam without purchasing the ridiculously expensive gun.

Very nice write up.

Originally Posted by Focal E46

Great thread. But I would recommend checking to see if your subframe is already cracked before buying that stuff because you might have to end up welding anyway

THis....But Def something I will do next. Cheap and easy. Thanks

Thanks, hope it helps.

Originally Posted by chriskuta

Cheers JeppeJ - I'm interested in the foam injection part at this stage. Thanks for sharing! Once filled and set this will be pretty hard I reckon and should help reduce and even stop further stress.

When dry the foam feels like very hard plastic. It will expand inside the subframe and make the area around the bolts rock hard. Preventing the bolts from moving and tearing apart the top mounts and the subframe. At least thats the theory.

Originally Posted by Focal E46

Great thread. But I would recommend checking to see if your subframe is already cracked before buying that stuff because you might have to end up welding anyway

Good point.

Originally Posted by aggieE46

Was it really necessary to use the Turner plates, too?

Thanks for the write-up. Where did you get the foam? I searched the PN a few places but couldn't find a place to buy it. Did you just go to a dealership?

You probably don't need the plates if your subframe is ok. But my car will see a lot of hard track driving so I did it just to be sure.

Any BMW parts store should be able to order it for you, mine did. It's BMW part numbers. Otherwise try your dealer.

Originally Posted by Hartman

AWESOME alternative. Now we just need to find a good way to apply the foam without purchasing the ridiculously expensive gun.

This is a problem. Maybe it does exist somewhere but I didn't find anything online or at the shops we have here where I live. Maybe I should start mass production of the gun I made...

3M 08571 applicator gun
http://www.autobodytoolmart.com/3m-m...1-p-15298.aspx

Thanks again. I'll definitely be doing this ASAP.

So if you have a torn subframe you just use the epoxy and sandwhitch the plates on to the ripped sheet metal. Dont get it.

Originally Posted by n2Bimmer

So if you have a torn subframe you just use the epoxy and sandwhitch the plates on to the ripped sheet metal. Dont get it.

I doubt it. I think this is more of a preventitive measure.

Yep, this is preventative.

Originally Posted by aggieE46

Yep, this is preventative.

oh, okay. but damn its alot of work

I'll quote you on that when your subframe tears and you're having to pay to have it fixed and THEN have the kit welded in

It's not that bad. Might as well redo all your rear suspension and subframe bushings while it's out. Much easier than while it's in the car.

Originally Posted by n2Bimmer

oh, okay. but damn its alot of work

Originally Posted by JeppeJ

If you plan on doing the right side as well you don't need to look for this hole on the right side. It isn't there, I have looked..

So you didn't get access to the front right area?

Originally Posted by JeppeJ

Inject two cartridges into the right hole also if you want to reinforce that side as well like I did.

When you say two cartridges you mean one lot of Structuring foam 83 42 0 307 530, not two lots?

Question, where you cut into the frame on each side, how come the foam didn't piss out from these openings.. or does the foam go into a deeper channel?