You've probably not seen an E30 suspension failure like this before

[ForcedFirebird]

Neat, you're finding the fatigue limits of the chassis. It's useful to see where it's happening as these cars age. Running it hard and using super stiff bushings was bound to do that eventually. Gotta either reduce the forces or increase the material thickness.

That's just it. These poor cars are and my age ratio aren't doing so well these days. Lol.

Years of abuse, weathering etc. There's an ole rumor that BMW used to like to use old used up m10 blocks because they "seasoned".

My machining mentor mentioned something along the same lines. He told me modern manufacturers are in such a rush to get everything done, the blocks hadn't even really cooled by the time they started machining them. Lol I don't know if he was pulling my leg, but he was certainly on his game, and drove a 4 second funny car until he was 70. He would make fun of my m20s, saying that his starter made 400 horsepower

[varg]

Neat, you're finding the fatigue limits of the chassis. It's useful to see where it's happening as these cars age. Running it hard and using super stiff bushings was bound to do that eventually. Gotta either reduce the forces or increase the material thickness.

[ForcedFirebird]

Dang! We ran an e30 in Chumpcar for 8 years with the same sub frame the whole time. We did have a bolt pull through the engine mount tab, but that was when the car went tail-first into a concrete barrier at Sebring ~110mph.

[bangn]

running coilovers by chance? that's a lot of transferred force!

[redneckvtek]

Found another new failure today. Rear bolts on front subframe are ripping out of the frame rails. Weld-nut on the drivers side is totally detached.

Bolts were tight but came out with no corrosion issues. Sway bar is Stock and the only thing I can think of that would apply a downward pressure to the rear of the front subframe?

[ccarey3]

Stock M20 running rubber mounts with reinforcement cups driven very hard in New England winters:

[redneckvtek]

what subframe bushings you running?

Condor

[moatilliatta]

Ok i have a new one for y’all.

any thoughts on the root cause and/or necessary repair/reinforcement?

what subframe bushings you running?

[McGyver]

Are these failures all on extremely stiff suspensions on a track car? I would assume it's just the repeated force of slamming through bumps for hours.

[e30austin]

woah, i've never seen failures quite like the ones in this thread. i've seen the engine mount tabs rip off, primarily on the M42 and S14 powered cars, and have seen one sway bar mount rip off on an incredibly neglected '87 325i, that i parted out many years ago, but these are genuinely impressive. guess i should inspect the one on my red car, next time i have it on the rack. that car gets driven harder than anything else i've ever owned and, likely, will ever own.

[redneckvtek]

Ok i have a new one for y’all.

any thoughts on the root cause and/or necessary repair/reinforcement?

[kronus]

I'll post up once we get our reinforcements onto the spare subframe, we should be good to do it in-house. Definitely no intention of reusing our original subframe - the side that cracked instead of ripping out has a lot of stress cracking going all over the place.

Car is a multiple Lemons race winner in the competitive CA field, despite not being supremely fast in a straight line. Reliability and stint length help :)

Interestingly enough, I ran a different E30 in lemons for about a decade, with an M30, stock brakes, 225s, and absolutely no regard for gently easing over curbs. We parted it out recently, the front subframe had no damage at all.

[redneckvtek]

Here is my failure and repair. I was lucky that I caught it (twice) before it actually failed.

Failure:



Drill Stopped and TIG crack


MIG reinforcement welded



Your subframe looks too far gone to repair TBH. I would start fresh and reinforce immediately. It does appear that a decent curb hit is what did it in, but the left side took the hit and both sides failed.
This repair was done in 2017 and 2018 and (knock on wood) has not been an issue since. I race ~ 60 hours per season per car on 245 RS4. Generally at the pointy end of the chump field. Not sure how that compares to your car's use case.


If you don't have the time/equipment to DIY this repair, there is a local shop called Backyard Bavarian that sells complete reinforced front/rear subframes, powder coated and all, for a reasonable price. Facebook/Insta is how to contact or PM me and I can send you his number.

-Chris

[kronus]

bonus uneventful failure video: https://www.youtube.com/watch?v=FNOpWFDK-UI

[kronus]

I nut&bolted it before the event and didn't see anything of particular note up there.. definitely didn't look closely enough to note cracks beginning to form. Reasonable ideas regarding spreaders and other reinforcements. I'm wondering what that will end up transferring the load to, though.

I did find an old s14.net thread featuring stories of similar failures. They seemed to have some concern about the metallurgy of the subframe post-reinforcement. The torn-out balljoint failed entirely around the weld, which would have been a harder and more brittle part of the metal than the rest of it. I'm worried that a similar result will occur around the edge of whatever reinforcement finds its way on the replacement for this subframe.

Kind of wondering if going back to non-solid CABs would be a decent compromise.