Will all E36s (non M) that are autocrossed need to have the rear subframe mounts reinforced?

My 92 325i tore out two of its mounts after one autocross and I haven't even had a chance to put race rubber on it yet. I just bought the car last fall, and I know it is old and high millage but, this realy seems like a serious problem to me. I'm new to BMWs but I've been autocrossing Fieros for years and I've never even heard of one of them have a major (or minor) suspention or drivetraine part just rip off the car even with large v-8 transplants. I thought that the 325 would be a step up from the POS Fiero, going to a faster car in a slower class (fieros are very poorly classed in stock and SP)

Did I just get stuck with a lame 325i, or is this "normal"?
If this is "normal" then how can BMW get away with making shuch crap without wrecking their reputation?
Last question, how much repair work needs to be done to the torn mounts before the reinforcing plates are welded on? (Do I just weld it all back together and then put the plates over top or is there more to it than that?)

Is it "normal"? No. It is more common than it should be? Yes. The subframe bushings are rubber and will eventually tear. When they do there will be play and this will cause stress on the subframe until it eventually developes cracks. Once it starts to crack, it's not long before separation occurs. I hear that this may even be a problem with the E46 models now that they are beginning to show their age.

Welding in the subframe reinforcement plates and getting poweflex bushings are the best preventative measure. Too late for you, but a good idea once you get the welding repairs complete. Good luck with those. I hear it is expensive to have the subframe properly repaired once it rips.

I have autoxed about 100 runs so far without any subframe issues (I hope). But I have a low mileage 96 model. I am not going to press my luck. I am going to get the powerflex bushings and the reinforcement plates put on before next season.

While it's not normal, it's not abnormal. Most of the non-M shop race cars have torn the chassis at the subframe mount points at one time or another before we put new subframe mounts in them.

In theory, if you keep the subframe mounts in top shape (replace them when they go bad) then it would never be a problem. They can go bad as early as 60k. Also, most of the problem lies within powertrain loads as opposed to r-compunds and hard cornering. This is why it's most common in manual transmission cars, especially those with a limited slip.

So does anyone know a shop in Ohio that would be familiar with this kind of repair work?

would powerflex bushings, being stiffer than stock, distribute the forces more evenly than rubber? if they spread the load more evenly, perhaps you can buy some time instead of tearing the same mount first al the time.


Is it "normal"? No. It is more common than it should be? Yes. The subframe bushings are rubber and will eventually tear. When they do there will be play and this will cause stress on the subframe until it eventually developes cracks. Once it starts to crack, it's not long before separation occurs. I hear that this may even be a problem with the E46 models now that they are beginning to show their age.

Welding in the subframe reinforcement plates and getting poweflex bushings are the best preventative measure. Too late for you, but a good idea once you get the welding repairs complete. Good luck with those. I hear it is expensive to have the subframe properly repaired once it rips.

I have autoxed about 100 runs so far without any subframe issues (I hope). But I have a low mileage 96 model. I am not going to press my luck. I am going to get the powerflex bushings and the reinforcement plates put on before next season.

Stiffer with less play and less chance of cracking. Here is some info and picks on the E36 subframe problems.

http://www.tcdesignfab.com/E36%20diff%20mount.htm

I had inherited our familys old 92 325i...and it had the rear subframe ripped out.

I reinforced it with my own laser cut .090" Stainless Steel Plates to repair/patch, and installed the PowerFlex SubFrame Bushings...

http://www.cardomain.com/ride/2084000

To press out the OEM bushings, it was a real PITA.

i ended up using rope and a 3foot vice (circa 1940s) that i sourced from a machine shop.

I'd highly recommend this set up!

Cheers,

-ELI

I installed powerflex subframe bushings it was a major pita to get the old bushings out without the right tool. Finally Got them out though new ones went right in with easily though.

ELIBEEMER,

Nice work! Did you do the welding yourself?

ELIBEEMER,

Nice work! Did you do the welding yourself?

Thanks...

Yes sir, I TIG welded the patches on myself while the car sat in my driveway.

I used a special welding rod( that the welding supply shop) sold me to better fuse the Stainless patches to the CRS body.

Well, I finally got around to taking my car appart. I have the right front and left rear mounts torn loose. Now that I have the car apart I now see that the mounting points are/were also welded at the top of the capured nut not just the bottom.

Those of you who have repaired torn mounts how did you address the problem. Did you just weld the bottom and put on the reinforcing plates? Or did you some how dig into the car to gain acces to weld the top also? If you did reweld the top how did you access it?

I'm still waiting on the reinforcing plates I ordered from BMW to come (ordered them a couple of weeks ago)

Well, I finally got around to taking my car appart. I have the right front and left rear mounts torn loose. Now that I have the car apart I now see that the mounting points are/were also welded at the top of the capured nut not just the bottom.

Those of you who have repaired torn mounts how did you address the problem. Did you just weld the bottom and put on the reinforcing plates? Or did you some how dig into the car to gain acces to weld the top also? If you did reweld the top how did you access it?

I'm still waiting on the reinforcing plates I ordered from BMW to come (ordered them a couple of weeks ago)

I used the BMW reinforcement plates (available from turner, your local dealership, etc...) on the bottom. I also made cuts into the sheet metal above (+ shaped cuts above the subframe mounts) and welded the detached threaded collar bit back into where it belongs on the top side.

My 92 hasn't had issue again yet. Its definately among the more stressed of the 92's around now. ;)

I used the BMW reinforcement plates (available from turner, your local dealership, etc...) on the bottom. I also made cuts into the sheet metal above (+ shaped cuts above the subframe mounts) and welded the detached threaded collar bit back into where it belongs on the top side.

My 92 hasn't had issue again yet. Its definately among the more stressed of the 92's around now. ;)

hey techno...just curious but whats the reason for the plus shaped cuts? i am also suffering from this PITA so any input would be great...thanks.

One of my friends just bought a 92, and we're gonna take down the subframe here shortly to have a look at his torn subframe. These cars are seriously garbage. I don't think my 4 banger had enough power to cause much stress to my subframe, but with my swap, I am seriously worried. I shoulda had the plates welded in while I had my subframe down... Now I'm gonna have to pay for an alignment again.

hey techno...just curious but whats the reason for the plus shaped cuts? i am also suffering from this PITA so any input would be great...thanks.

+ shaped cuts meant I could bend the metal back far enough to get the end of the mig down in there for welding. I could then fold the metal back down and weld it back up without leaving gaping holes in the sheet metal. :)

there were already small holes in the right places for access. the holes just weren't big enough for a welder to get in there. . . but they were big enough to get the end of a pair of tin snips in...

I should see if I have pics around of the butchering, erm, I mean repairs. ;)

+ shaped cuts meant I could bend the metal back far enough to get the end of the mig down in there for welding. I could then fold the metal back down and weld it back up without leaving gaping holes in the sheet metal. :)

there were already small holes in the right places for access. the holes just weren't big enough for a welder to get in there. . . but they were big enough to get the end of a pair of tin snips in...

I should see if I have pics around of the butchering, erm, I mean repairs. ;)
That's actually a pretty ingenious idea. I'll have to use that next time. :buttrock

But Why a +? Why not a triange or square (2 or 3 weld seams instead of 4, and only one bent piece of sheet metal instead of 4) I'll go have a better look in the garage tomorrow. Are the front mounts under the back seat or the trunk?

But Why a +? Why not a triange or square (2 or 3 weld seams instead of 4, and only one bent piece of sheet metal instead of 4) I'll go have a better look in the garage tomorrow. Are the front mounts under the back seat or the trunk?
That's what I was thinking, but I guess it depends what the area is like that you are working with. Some incisions may work better than others.

But Why a +? Why not a triange or square (2 or 3 weld seams instead of 4, and only one bent piece of sheet metal instead of 4) I'll go have a better look in the garage tomorrow. Are the front mounts under the back seat or the trunk?

A + because why not. :dunno
3 could work. I don't see how you'd get away with only 2 cuts though.

IIRC, the front mounts are near the seat belt anchor point line in the back seat of the coupes.

A + because why not. :dunno
3 could work. I don't see how you'd get away with only 2 cuts though.

IIRC, the front mounts are near the seat belt anchor point line in the back seat of the coupes.
Two cuts at a 60-90 degree angle I think would work depending what the area is like that you need to get to.