Remove rear sway bar? Horrors!
 

I have a 318/332ti with TC Kline double-adjustable suspension. When running against track-prepped E36 M3s, I find I can't get on the power quite as fast as they can at corner out. One suggestion was to REMOVE the rear sway bar and install a Bimmerworld rear camber kit, presumably to get more traction at the rear. I see from scanning some threads here that autocrossers often disconnect the rear swaybar.

Anybody done this for a track car?
How did it work?
Any other considerations on what to do with the rear suspension settings--such as stiffer or softer shock adjustments with a disconnected rear sway bar?

If I do the rear camber install, that should let me run bigger tires, n'est ce pas? Right now, I'm limited to 225 or 235x17s, depending on the sidewall.

Yes, I asked TC Kline. They haven't answered.

I disconnect the rear for autox and it works well there but at the track I reconnect the rear bar and stiffen the rear rebound. I have TCK singles. I only have a few track days experience so far but the car feels good to me and my instructors seem happy with my progress.

Also, I can fit 245/40 17s pretty easily on 17x8.5 et41 wheels. I have not yet installed any sort of rear camber/toe adjusters.

I can barely fit my fingers between the fender lip and the rear tires. Even my 235x17 street tires hit a little. How'd you get those big tires in there?

These were 245/40 Hankooks, I literally just bolted them on, no issues at all. Rear ride height is fairly low. I had a good bit of room between the wheel and fender, much more room in the rear than the front. It was getting close to the trailing arm though. Running 17x9 et42 with a 255/40 might start to get tricky.

Did you swap a different subframe/trailing arms when you did the engine? Some of the Z3 trailing arms stick out further and could cause wheel fitment issues.

We're just opposite, then. I got plenty of room up front but no room in the rear.

I took my rear bar out a couple years ago...no regrets here. I do have some sort of eccentric bushing/camber kit in the rear (installed by p.o.). I do more track events than autox, fwiw.

I read once the Old E30 M3 touring cars, did not run a rear bar, they ran hellish stiff springs.....

Same suspension more or less... .


Dave

I'm going to chalk that up to an internet myth.
My Grp A car is still pretty much as it ran in the BTCC and its rear sway bar is firmly in place and was connected. My car is an early chassis ('87 construction) so no adjustable bars, but the later ones had adjustables.

Every ex-works chassis (DTM, WTCC, BTCC) I have seen personally and in photo had a rear sway bar in and connected as well.
Now thats not saying some didnt do away with it (I haven't seen every one),,, but I don't think I have ever seen or heard of one without.

Cheers
jimmy p

I haven't run a rear bar in years. My mechanic is the chief mechanic for RSR racing which was running the mini coopers in grand-am, but he has also worked with Automatic racing and other BMW racing teams going back about 10-15 years. He swears by removing the rear sway bar on cars with this kind of suspension setup.

Typically, you'll want to go with a stiffer spring to offset any loss in roll resistance. I think the general TCKline recommendation for our cars for 500# rear springs is to soft. I also think the full length TCKline springs are to long for the rear of our car. You end up taking out the spring perch and losing any adjustability. Best to go with their shorty springs, or something comparable, and probably in the 650 to 700# range for Koni DAs with the height adjuster collar so you can properly balance the car.


The other thing you can do to try and get more rear grip is to soften dampening and rebound. Softer suspension on a particular end of the car usually helps with increased traction on that same end. Removing the sway bar lets the rear squat down better. I'd go with the Ireland Engineering weld in camber/toe adjustments. I run with slight toe-in and around -2 degrees of camber in the rear.

You should be able to run a 245 or 255 with rolled fenders and a camber kit. As long as it is shorter than a 40. 245-45 17"s rubbed on my car, but that tire is way to tall to be a good performance tire anyway. 245x40 would have fit without issue.

Wish I still had the book, The chapter was written by one of the principal mechanics for BMW's race program. All I know is I tried the specs he mentioned on a 200SX (S13) which has nearly identical suspention to the TI and the car owned its class for 2 years.. Unfortunately it got borrowed.. :(

With no rear sway bar and stiffer spring, what kind of spring rate are you running up front? Do you put a bigger sway bar up front?

I'm running 500# in the rear, but really need to be up at 650 or so. Not sure what the front springs are. My car still has the TcKline recommended spring rate, which I feel has the rear end way to soft compared to the front end of the car.

Running an H&R adjustable front bar full soft I believe.

The TcKline setup was a great setup to start with. pretty forgiving, and for the most part the car is neutral. The issues with their "wonky" spring rates only came up for me when I started running hoosiers and really pushing the car for timetrials.

I have tck singles 400f/600r, eibach front bar full stiff / no rear bar. At autox I find the car to be neutral to slight oversteer. Swapped M3 hats on the front give me -3deg camber, 6deg caster.

What I really need is to weld in rear alignment adjusters and get my rear toe dialed in better.

I tried 400 and 500lb springs in the rear and, like mohaughn said, the rear felt too soft.

I have (nearly) the same setup myself now. Love it. TCK S/A's, 400F/ 600R; no rear bar, front bar is the 27mm(?) Sport bar (came stock on the car) with the M3 endlinks attached to the struts.

With 'old' tires, the rear end is getting a little skittish. But when running decent tires, it is excellent.

Im gonna jump in on this, Im running my ti in g stock for auto-x, so im on stock everything, would taking out the rear sway bar be a good idea for me?