I have a 1994 318i that's being caged and prepped for running in the 24 hours of lemons series (among other events). I'm new to BMW and the common things that should be addressed. I was hoping someone could look over my plans for refreshing the chassis and maybe point out things i'm missing or things I've listed that might not be necessary.
1. Rear Subframe plans
I believe the chassis I have is sound, meaning no existing tears. However I'd like to add the reinforcements anyway. Plan is the following:
i) rear subframe reinforcement plates (turner/VAC/etc). Clean area and weld in.
ii) from the inside reinforce the mounting points and tie into the cage. Similar to this picture, though I may change the design slightly to suit my cage
iii) on the subframe itself, clean the whole unit, seam weld the subframe. I will also install the sway bar reinforcements from turner/VAC/etc.
iv) replace bushings before reinstalling. Will probably just use OEM to keep costs sane.
2. Other rear end plans.
i) RTAB area. Replace bushings and weld in reinforcements
ii) camber arm reinforcements. Weld in plates from turner/VAC/etc
iii) weld in shock tower reinforcements
3 Front subframe
i) remove, clean, inspect and seam weld front subframe
ii) weld in front subframe reinforcements from turner/vac/etc
4. Other Front end plans
i) Shock tower BMW OEM reinforcement plates.
ii) DIY shock tower brace.
iii) DIY X-brace. Car is being engine swapped to a non-bmw engine, so the stock BMW one may not fit. But I can mimic the design around what I install.
5 Misc other items
i) I know I will likely have to replace control arm bushings as well, but will inspect first.
ii)I should probably do diff bushings, but again, will inspect first.
Thoughts? Trying to keep costs sane throughout this all. But I'd like the chassis to be race ready at the same time. If you had to focus on certain items first, where would you start?
Most of what you have planned is massive overkill. If you paid a shop to do all of that it could total $10K or more, including the cage.
It seems like the "steelitus" solution is strong on this forum. I don't think W2W cars need the jungle gym of "subframe tie-ins" that others here feel are necessary. People like to add tubes and tubes and tubes...
The E36 above was caged in 2006 and hasn't had any structural issues since then with 315mm Hoosiers, 500 whp, aero loads, etc.
Just reinforce the known weak points: rear subframe mounting points (see above) on the chassis, front subframe engine mounting pads (see below), and the RTAB buckets if you are feeling adventurous.
If you want to make a bomb proof car add some plate to the top of the strut towers and the top of the rear shock towers - I've seen both areas crack in some rare cases.
You might be over thinking this... unless your budget is so big that it doesn't matter.
Cheers,
Terry Fair @ Vorshlag Motorsports
Terry:
I have typically seen the front strut tower and rear shock mount reinforcement plates simply sandwiched in place with the mounting bolts -- as opposed to welded. You think welding is necessary in those spots?
Overthinking is my specialty, which is why I was having someone sanity check me.
I'm doing everything myself. i'm good with a welder, and the car I'm currently racing has a cage I bent and welded. So cost won't be that horrendous. You're probably right that tying in the rear subframe to the cage is a little overkill. We'll just add that to the "if I have time and want to look cool" pile.
The bushings I definitely want to replace. The ones in the car are looking a little tired.
This is one of those "Necessary" vs "Preferred" things.
Like the RSM Reinforcement Kit we make for the E30/36/46 - that is made to be bolted in. There are other kits made to be welded. Each has its place.
Terry Fair @ Vorshlag Motorsports
Bookmarks