How bad is the E36 subframe mount issue?

[ApexEight]

I have a '97 328i that I would like to autocross, I'm just afraid of tearing out the rear subframe mounts since I'll be driving hard and also because I don't think the subframe bushings have ever been replaced. The car is pretty much stock with 240K miles. New struts up front, new shocks and shock mounts out back, and delrin RTAB limiters on shot stock RTABs. The car feels pretty solid and doesn't have any rust; its been in the southeast its entire life.

What do you guys think?

[MisterM52]

thinking the same, in similar situation however the northland twisty roads make up for auto x and some track days at hamptons down, but nothing serious.

[MINIz guy]

I'm interested in what everybody says.

I want to believe that as long as the bushings are fresh, you can get away without doing the reinforcements as long as the subframe isn't already cracked. I can't back this with hard proof though.

[ApexEight]

I'm interested in what everybody says.

I want to believe that as long as the bushings are fresh, you can get away without doing the reinforcements as long as the subframe isn't already cracked. I can't back this with hard proof though.

I agree with your sentiment. Fresh bushings means less subframe movement which means less stress on the mounting points which means less chance of tearing them out. I wonder if having bushings with less compliance than stock (polyurethane, solid) would increase or decrease your chance of mounting point failure.

Too bad I'm pretty sure my subframe bushings have never been changed.

[scooper]

weld up the M3 subframe plates. At least change your bushings.

[MisterM52]

how much work is involved/cost?

[MINIz guy]

weld up the M3 subframe plates. At least change your bushings.

I feel that a lot of M3 guys just say this since their M3's don't have failures.

I looked back at what some racers said:
1 had 290k on his 95 M3, bushings were alright and he had plates: no damage
1 had 85k on his 325is, ripped 3 mounting points and suggested I do it
1 had a 97 M3, recommended I do plates if I'm running an extreme set up
1 had an M3, commented that their RTAB bungs were cracking after running on R-comps and reinforcements there would possibly be needed

I'm only hesitant due to cost. I can do bushings myself, but not weld in plates.

[somebody5788]

I'm dang near 200k miles on original bushings and the occasional autocross in my 97 328is with factory M Sport suspension package. I intend to do the plates before I go to a sticky tire and new shocks/struts.

[z25is]

I know of two auto cross'd e36's that tore their subframe mounts because they were not reinforced, if you're going to beat the car then you want to do this job for sure, along with new subframe bushings. I did it on my 332is before swapping in the S52 because I knew it wouldn't hold up in the long term to the extra power increase.

[ApexEight]

I know of two auto cross'd e36's that tore their subframe mounts because they were not reinforced, if you're going to beat the car then you want to do this job for sure, along with new subframe bushings. I did it on my 332is before swapping in the S52 because I knew it wouldn't hold up in the long term to the extra power increase.

Damn.

I wonder if 328s are more prone than 325s due to having more torque.

Thanks for sharing your experiences guys.

[z25is]

Damn.

I wonder if 328s are more prone than 325s due to having more torque.

Thanks for sharing your experiences guys.

Absolutely, more power = higher risk

It's a lot of work, but once you're all done with it you'll be happy, it's well worth the extra peace of mind.

[ogkush420]

this question seems to come up frequently

I myself was almost killed by a damaged rear subframe letting go of the trailing arm.... in a 318 i think it all comes down to THAT car specifically and the condition of it and how much fatigue/ stress the chassis has received over its life, as well as rust as well as your bushings its far more complex an issue then wether or not re enforcement plates have been installed

[boarder2k7]

I myself was almost killed by a damaged rear subframe letting go of the trailing arm....

What happened?

[MisterM52]

What happened?

he survived and lived to tell the tale and aspire to meet me one day with his broken subframe in pieces loaded into my wheel barrel full of shitty broken plastic parts that bmw used where plastic does not belong and didn't re enforce where they should had, all of which i plan to take with me in rolling my wheel barrel full of parts stampeding infront of the bmw factory and throwing them through their windows and shouting obscenities in German. This is of course when Mr. Hyde wants a few more German Girls..specially the southern ones.

^ Based on a True Story with Tom Hanks playing the role of Hyde.

[Team Neverlift]

Reinforcement should be done. No way around it.

[MisterM52]

or just buy an m3?

[Pyropete82]

It's an 6-8 hour or deal, you'll need to drop the whole rear end, and maybe gas tank if you don't like rolling dice. Overall a field welder should be able weld plates on in no more than 2 hours. On the ground it may take longer. My mechanic quoted $500 for the on and off. It's a pretty straight forward mod but takes a lift for the day


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[PITT M3 RR]

Reinforcement should be done. No way around it.

Yes, custom plates or the BMW kit for $99.00.

you can unbolt shocks, trailing arms, emergency brakes, sway bars and drive shaft and lower the whole deal on a floor jack. Cake!

[ApexEight]

So I've been doing some more research and read a comment on another forum from a guy that said the pre-1996 non-Ms are the ones that are at risk for the failure and that starting with the advent of the 328 the weak subframe mounts were addressed. Is this true?

[MINIz guy]

So I've been doing some more research and read a comment on another forum from a guy that said the pre-1996 non-Ms are the ones that are at risk for the failure and that starting with the advent of the 328 the weak subframe mounts were addressed. Is this true?

Well, you can see an extra layer of metal (reinforcement plates) on the M3's. You don't see that extra metal on 328's.

[bmw4life92]

My 325i coupe had pretty bad rust in the pockets for rear trailing arms and 2 of the subframes chassi mounts were torn when I bought it.
Welding in rather large new pieces of the chassis can be expensive if you let a professional do it, I had a guy with welding skills do it and he welded on reinforcement plates too, on the new subframe- and RTA mounts, so that shit wont happen again x)
You should put on some Powerflex bushings also, if you are going to drive it hard on the track. Those old OE bushings will not last under pressure, and you will start wearing more on axles and diff etc, like my 325i, one of the rear axles are shot in the X-joint cuz of being driven with bad bushings and loose subframe, I suspect the old subframe bushings had enough sideways play in them that the diff would twist the subframe more and more until the point 2 mounts were torn off.
Just sayin it might be cheaper in the long run to do a few tweeks now, instead of wearing out very expensive components.

Best of luck