e30 Chassis Reinforcements

[atmh]

Done a bunch of searching, I know the knowledge exists, just haven't had much luck finding it:

I'm looking for input on what weak points have been identified in the chassis, and/or what people have done to stiffen the chassis (unibody) of the e30 for track or high horsepower abuse? I think some people have welded in e30 Convertible bits, but I can't find a list of what parts are used, and I think some of the suspension mounting points have been or can be reinforced via sheet metal kits from aftermarket suppliers, but I haven't seen a good synopsis of what has ultimately worked to get the chassis to handle hard track use or high horsepower (or both). Certainly a welded in roll cage is the ultimate solution here, but I'm really looking for everything else that can be done before (or in addition to) a cage. A long long time ago I also remember a discussion about using an M3 windshield bonded in place to add stiffness, rather than the floating/gasket of other e30s.

So far I see reinforcing the subframes, strut tower bracing, and an X-brace for the front subframe/control arms. But is that really it? It's hard to believe that the chassis can't benefit from additional reinforcements between the front and rear suspension.

In a few months I'll be tearing down my car to nearly a bare chassis for rust repair, and it will be a great opportunity to weld in any needed reinforcements at that time. For what it's worth, my build plan probably will result in ~400+hp, ~245 width tires, and will see track and autocross use, but is not a dedicated track car, so a cage is a "maybe", not a "definitely". Car started life as an '84 325e.

[atmh]

SMH. I tried a different search technique (using google, rather than the internal search function in the forum) and found what I was looking for:

https://www.r3vlimited.com/board/forum/general-forums/track-autox/153848-chassis-reinforcement

https://www.r3vlimited.com/board/forum/general-forums/members-rides/340916-chassis-stiffening-chassis-gussets-and-giving-thanks

https://www.r3vlimited.com/board/forum/e30-technical-forums/convertible-technical-discussion/101327-stiffening-the-convertible-chassis

Still interested in anything that anyone can add beyond these three threads.

[TobyB]

What I didn't see there (there was a lot, I skimmed)
was the attachment of the front inner fenders and
support structure to the firewall and a- pillar structure.

In other words, how the suspension loading on the front of the car
gets transferred into the box of the cabin.
On well- used PRO3 cars, there has been cracking and
separation there, as the cars are just... soft.... for hard track use.
And reinforcement is not permitted.
The cabrio brackets might help some, but from seeing some
of the cracks, beefing up the transition seams
(I recall cracks along the spot welding) would help with the
long- term fatigue damage.

t
hasn't done anything like this, but is thinking about it, too.

[atmh]

What I didn't see there (there was a lot, I skimmed)
was the attachment of the front inner fenders and
support structure to the firewall and a- pillar structure.

In other words, how the suspension loading on the front of the car
gets transferred into the box of the cabin.
On well- used PRO3 cars, there has been cracking and
separation there, as the cars are just... soft.... for hard track use.
And reinforcement is not permitted.
The cabrio brackets might help some, but from seeing some
of the cracks, beefing up the transition seams
(I recall cracks along the spot welding) would help with the
long- term fatigue damage.

t
hasn't done anything like this, but is thinking about it, too.

Cool, thanks this is exactly what I was looking for.

I am also considering seam welding as a final step (right before final paint when the chassis gets fully stripped). Just want to get all the piecemeal reinforcements in place before that final strip/weld/paint step.