Taming Auto-X Body Roll on 91 318i

[Petebee]

Hey guys,

I autocross my DD 318i in STX and need a bit of advice on getting rid of some of the body roll I experience during high load, tight corners. Here is the current setup:

H&R Sports (remember a DD ;)) with Bilstein Sports
Stock Sway Bars
Stock Spring Pads
All new OEM bushings and stuff (subframe, RTAB, strut mount, upper shock, engine mounts, sway bar end links)
M3 CABs
New control arms

I just refinished a set of bottlecaps that will be receiving a set of 195/60/14 Falken Azenis.

Changing springs is not an option. Would I gain anything by going to a larger front sway bar? I've seen that E30 cabriolets come with a larger (21mm) bar that I could probably find pretty cheap.

I've also seen the E30 M3 sway bar end link mounting tabs from AKG. Would these be worth looking into? Anyone have a link to a pic that actually shows how this looks on the car?

Done quite a bit of research and it seems like stiffening the front could help to reduce the body roll while keeping the balance neutral or slightly loose in the rear.

Our local SCCA chapter has our next autocross at the Michelin tire testing facility in SC and I want to be prepared :mrgreen:

Thanks for your help. Here's a pic of the car:

[gearheadE30]

The sports are a big part of the body roll, honestly. If you don't want to change that, then the budget ber setup is the cabrio car up front and either no bar rear or the iX/M3 rear bar depending on your driving style/track layout etc. The cabrio car actually has different geometry than the M3 front bar, even though they are the same size, and it is a bit stiffer. If you have the ability and time, the M3 front bar tabs are very worthwhile.

If you really want to get rid of roll, though, IE and others sell adjustable bar kits. I'd go with the 25/22 personally, unless you could find 25/19 or something. For that, you will need to do some reinforcement.

[Petebee]

Thanks Gearhead. I know...coil overs or stiffer springs would be the best route, but I'm trying to balance daily use comfort and decent performance. No biggie if I'm not winning my class.

I figured the stock bar in the rear was okay since the M42 cars are pretty light in the rear already.

Quick question on the cabrio front bar...does this require unique mounting brackets or end links, or is what I have with my stock bar reusable? Same question if I weld on the M3 tabs? Can I reuse end links and mounting hardware and simply attach them to the strut tower?

[StereoInstaller1]

M3 end links are quite a bit longer, as they attach to the strut tube, as you (seem to) know...so get adjustable "heim joint" links.

Mounting urethane bushings on the stock subframe is kind of a pain in the butt.

What I have had sitting for like 2 years (and now I have a fucking LIFT at my disposal, WTF?) is a modified subframe, with metal plates welded where the sway bar mounts go, so no more "tab A into slot B" bullshit, and can change sway mounts/sizes easily with Energy parts...now to get the tabs welded on, so I can finally get the cabby sway bar on!

Damn, I swear, getting things done on my car owns me.

[87e30]

I know you say switching springs isn't an option... but do it.

Try riding in a car with H&R race and then decide if they are too stiff for street or not. If you are auto-xing your car then you must like driving it and I'm sure you'd enjoy the race springs. Especially on those fat tires you won't have a harsh ride.

[JGood]

I know you say switching springs isn't an option... but do it.

Try riding in a car with H&R race and then decide if they are too stiff for street or not. If you are auto-xing your car then you must like driving it and I'm sure you'd enjoy the race springs. Especially on those fat tires you won't have a harsh ride.

That's a very subjective issue. Not everyone enjoys bouncing around. I have an hour commute to work. When I take my DD with H&R sports, it's not bad. When I bring my track car to work every few months with H&R races, my ass feels like I got raped. Granted, the fiberglass seat doesn't help, but still...

[wolfgangstbd]

i ride in my friends car with coils, solid bushings etc all the time and it feels the same as my friends mustang with springs. just louder. the only thing that gets rougher on the ride is you bounce around a bit with the races. but assuming you have sport seats and pretty beefy tires the ride isnt gonna bother you much

[Aptyp]

shorter modded shock/struts, or good sway bars.

[Petebee]

Thanks for the input everyone. I agree that shorter springs and larger sways would cure the roll, but I still have to live with the car...some of the roads I take to work just plain suck.

Plus there is the financial component, too. If I can get the larger diameter front bar and use stock rubber bushings it is quite a bit cheaper than springs and/or a complete aftermarket sway bar set.

Do you think the cabrio front bar would help at all?

[gearheadE30]

yeah. You can use stock links, but you won't see the difference quite as much. You will definitely be able to feel it, though.

Also, you might want to consider some camber plates. I'm partial to Vorshlag ones. With as much body roll as you have, the car probly understeers a bit because body roll=positive camber on the outside wheels. Plates would help keep the tire more square with the road at autox, and you can adjust them back for road use to save your tires. Granted that won't fix the body roll at all.

FWIW I run GCs, Bilstein sports, cabrio front bar, ix rear bar, vorshlag plates, and poly everything. I don't have a huge issue with it on the road, but with a track seat it is a bit stiff. 15" tires help a ton, though.

[jms16v]

22/19 swaybars make a pretty big difference. I'm on h&r race/bilstein sports with ST 22/19 sways and there is very little body roll at tight/fast turns.

[p0cket penguins]

Jstock springs, 22/19 st sways, mason front and rear strut brace, mason x brace, poly everywhere, billy sports, and subframe/sway reinforcements