Safe to drive on this?

[McGyver]

please try not to be safe.

ftfy

[2mAn]

How are we looking deutschman?

[mr2peak]

He's busy putting in the subframe I sent him

[varg]

How does that even happen to a car like OP's (a 318is)? To my knowledge rear subframe fatigue isn't a common issue with E30s that aren't making that V8/turbo torque. I'm by no means an old-guard E30 guy who has seen everything, but I've never seen that in all of the myriad threads I've combed through, turbo or otherwise. I also haven't heard this kind of failure mentioned by the most knowledgeable E30 guys I know when talking about my upgrades and reinforcements, and I know a couple of E30 knowledge heavy hitters.

[MR E30 325is]

How does that even happen to a car like OP's (a 318is)? To my knowledge rear subframe fatigue isn't a common issue with E30s that aren't making that V8/turbo torque. I'm by no means an old-guard E30 guy who has seen everything, but I've never seen that in all of the myriad threads I've combed through, turbo or otherwise. I also haven't heard this kind of failure mentioned by the most knowledgeable E30 guys I know when talking about my upgrades and reinforcements, and I know a couple of E30 knowledge heavy hitters.

I had a similar issue (it involved the rear two diff mounting points on the subframe) when I had a simple M20B25 in an E30.

On the other hand, I rocked a supercharged S52 in an E30 for a while, damn near 400bhp, and never had an issue with my subframe.

There are a lot of variables that may go into why this occurs to some subframes and not others. I mean, we can discuss the effects of 1 of the diff to subframe bolts being every so slightly loose, the moment created about the centerline of the driveshaft, the subsequent acceleration and then resulting force from the bolt onto the subframe, and then the slight fatigue of the metal in the subframe over time. It would be much easier to see how this happens after that kind of analysis. Without this kind of education/understanding/experience I can see how it seems improbable.

That being said, I don't think the issue is common enough to worry about. But it definitely happens.

[varg]

Without this kind of education/understanding/experience I can see how it seems improbable.

Nice thinly veiled insult. I know full well what metal fatigue and moments are. I guess it just seems improbable to me that this would happen on a gutless 318 because I'm an idiot and not because I've seen powerful, abused cars where it doesn't happen

[nando]

I'd guess the bolts were loose or missing, putting extra stress on the two that remained?

another possibility is rust. but yeah, subframe failures on an E30 are vanishingly rare.

[MR E30 325is]

Nice thinly veiled insult. I know full well what metal fatigue and moments are. I guess it just seems improbable to me that this would happen on a gutless 318 because I'm an idiot and not because I've seen powerful, abused cars where it doesn't happen

Definitely not meant as an insult, my apologies for that. It's difficult to convey statements through the internet and typed words.

Anyways, like I mentioned in my previous post, I had a 'gutless' E30 that suffered from this issue. And a few years later I owned a powerful E30 that saw a handful of track days/Autox's that I owned for 8 years with the same subframe that never had the issue.

I was simply trying to explain how something can happen, in an area of understanding that I happen to be a professional in. Again, not meant as an insult. Sometimes I am a cocksucker on the forums, but this wasn't one of those times.

[djjerme]

I'd guess the bolts were loose or missing, putting extra stress on the two that remained?

another possibility is rust. but yeah, subframe failures on an E30 are vanishingly rare.

That sounds plausible, I've seen a few loose diff bolts on car's. But the only subframe failures I have personally seen has been on racecars, and even then, few and far between. With hard hits, it's usually the control arms or their pickup points that take the most damage.

[Fsnow]

It seems the only way this should happen is with loose bolts and/or a lot of rust.
Several companies sell weld on reinforcement kits for the rear subframe, so is it really that rare? Those kits are not legal in all types of racing.
When I have my subframe out I will probably do it just because of my ocd and wanting to keep the car forever.

[nando]

Those reinforcements are usually for the trailing arms (to stiffen them like the Mcoupe) or for the swaybar mount tabs. I've never seen a reinforced subframe kit? Unless it's for a 500hp+ build, I don't think it needs it.

[jpod999]

I have the Garagistic rear subframe reinforcement plates, they are just metal plates that get welded to the diff attachment points on the subframe:



Here's the kit: https://store.garagistic.com/e30-rea...l-reinforcment

My front subframe was cracked to hell, it surprised me being that it's an M42 car. Here are pictures of the motor mount tabs:

[Fsnow]

^Yeah like that. One peice for the top 2 bolts and a peice for each of the other 2 bolts. It may be a bit overkill but it's cheap insurance if u have the frame out and a welder handy.
Srs concept and maybe others sell these as well.

[nando]

Never seen them before. Probably not a bad idea for V8 swaps and big turbo V8 cars. But I can say, aside from this thread, I've never seen a rear subframe fail like that in 15 years of dicking around with E30s. So personally, I wouldn't worry about it too much (hell, my car still has the original swaybar tabs and mounts - even the bushings are original, never bothered to replace them because they are still in good shape).

[E30 Wagen]

I've seen a few failed subframes in person (fronts and rears), and I've seen this issue pop up on the forums enough to recommend that if you are dropping the subframe and have the resources to have it reinforced. Though, I suspect the cracking could be caused by worn mounts or other drivetrain components.