What is the factory rear sway bar doing?

[jaredmac11]

So most sway bars couple with an end link of sorts, but the factory sway bar for the e21 has some weird quad bushing setup that mates the sway bar with the trailing arms. How effective is this set up? Better than nothing at all? curious how this impacts driving characteristics.

[Tom D]

how you link the sway bar to the suspension is not that important. however, adjustable links are better for fine tuning.

[320iAman]

Sway bars(reduce suspension twist in e21's) keep all tires on the road contact surface more. As one side of the sway bar rises(outside) the other side presses downward(inside) in turns,, alpina bars help reduce nose twist in turns and plain look good and you can tell the difference in turns with or without, tower bars assist in keeping the towers level-untwisted in cornering, ect. Hard shocks and springs actually reduce the body roll as they are connected to the body. 320is models had both front and back sway bars along with other goodies-like a sport package. e21's are a little tail happy so rear sway bars help keep the rear tires on the road surface more than without. Kind of shaving points here to look at certain segments of the ride.

Randy

[dups]

and so does the '77s

[Tom D]

actually in stock form the rear sway handles worst then without........

[jaredmac11]

Pure stock? I am changing a ton in one go
. LSD, lowering spring, new strut inserts, new fresh rubber and poly, and this sway bar. I can of course just briefly disconnect the sway bar to get a before and after.

[autox320]

Pure stock? I am changing a ton in one go
. LSD, lowering spring, new strut inserts, new fresh rubber and poly, and this sway bar. I can of course just briefly disconnect the sway bar to get a before and after.

True, rear bar isn't always preferred depending on setup. We ran with factory rear bar, then Suspension Techniques, back to factory, then NONE. Even with 350 lb coil over springs front, had 400 lb rear, NO rear bar was fastest on autocross courses. Running an LSD rear and no bar allowed better hookup and weight transfer to the rear. Stock front bar allowed better turn in and grip without binding than a ST front bar. Once have stiffer springs and depending on ride height would need softer bars. Bigger is not always better. With stock springs, HR sports, could maybe run a larger front bar but IMO not worth it. In the rear no bar will be quicker. Disconnecting one side and trying it out is a good idea.

Sway bars should be thought of as fine tuning spring rate. Control weight transfer. Another is limiting droop if your hopping kerbs or rally keeps the front or rear suspension from full droop.

If can't make it exact, make it adjustable. Having adjustable allows to fine tune, even if just one hole change on ONE side.

Last but not least adjustable end links. Simple answer is they are for taking out bar preload. When connect a bar to both sides may have to force the last link on. Depending on ride height the last link may need a jack to connect. This is preload. Adding too much preload is adding unwanted spring rate. Sometimes adding preload is intentional. With adjustable links you set one side to keep the bar parallel to the ground. Adjust the other end to connect it. Once on the ground at ride height turn buckle just the one side to feel null ie no pre load. The turn buckle will spin free with no load and can be felt when turning. Set on one side or the other by a couple threads to avoid knocking sounds putting very slight pre load on the bar. I started doing this to avoid hammering the threads and heims. So slight it's not noticeable on scales to set a few threads one side or the other.

[cgifool]

Would having an open diff change the recommendation here of no rear bar over ST rear set to minimum oversteer?

Mine's off the car now, less work for me if I don't have to bother reinstalling.

[autox320]

Would having an open diff change the recommendation here of no rear bar over ST rear set to minimum oversteer?

Mine's off the car now, less work for me if I don't have to bother reinstalling.

I'd chose no bar with open diff. When cornering hard say around a turn around cone, the bar will actually limit one wheel in droop keeping it from touching the road as much. The wheel your leaning on will just sit there no power applied. The one in droop higher less on pavement will be the one spinning. One wheel wonder. If a VW this is seen in rears going around and looks funny, but it's ok cause not a drive wheel. In rear wheel drive especially in open diff = slow. Try and see if keeping the rear independent (no bar)works for you. I'll want to bet it does better.

[320iAman]

So most sway bars couple with an end link of sorts, but the factory sway bar for the e21 has some weird quad bushing setup that mates the sway bar with the trailing arms. How effective is this set up? Better than nothing at all? curious how this impacts driving characteristics.

The rear sway bar helps counteract the tail happy characteristic of the e21. Its not really something you can feel in day to day driving, yet when its wet and your cornering your speed is increased before your tail end starts to slide out, ask me how i know this ? lol The sway bars not only keep the inside tire down in a turn, they press the tire down on the outside tire much more so your ride is more stable.

I'd look at incrementally, they add a little more ride control. The alpina bar helps prevent nose twist in turns----its an incremental improvement and is noticeable if you pay close attention to driving in turns and so forth.

Randy

[captain awesome]

I would disagree that the rear sway reduces tail happy behavior, at least in my experience. I'm a HUGE fan of no rear bar, but so far my only experience is with the e30 chassis. With the rear being pretty similar to the e21 I imagine it will be the same result. On the road and in autocross the car is so much more planted and predictable. When I had it connected the rear would break loose SOOOOOO much faster without a ton of effort, especially aggressive on throttle lift oversteer. Because throttle lift oversteer is dramatically reduced without the rear bar you may not be a fan of it. Some like the sharp turn in you get, but I felt less in control at the limit. When I first tried this, it was with an open diff, but later when the LSD installed it was even better. I've tried connected and disconnected multiple times with the same result even with different tire compounds. This is all anecdotal, but the idea to disconnect the bar came from a TON of e30 guys putting in a ton of miles on track days plus autocross. I tried it to see if it made a difference and was pleasantly surprised.

[cgifool]

Thanks for all the feedback! I'm not a huge fan of tail happiness, so I'll definitely be giving this a try.

[jaredmac11]

This is such great feedback. Thanks guys so much.

Rear sport sway bar for sale, by the way... ; )

[mxl556]

Just wanted to add - my experience is that on a stock car (even with stiffer shocks) unless you have a limited slip, the rear swaybar negatively affects handling (due to less traction) and predictability.
There is a reason BMW removed them from later non sport models.

Max

[320iAman]

No, its something else, too big a roll bar,caster,camber,toe in misalignment ect , Bar not adjusted right and so forth. Anti roll bars give better traction on all 4 tires, straighter the better. he was talking about street driving , race driving is a different can of worms and suspensions get adjusted according to the track and tires too. Stock items in race conditions are rarely optimal. They did not delete the rear sway bar in 80-83's--the brackets are on the rear cross member and the trailing arms still have the holes for the end links --they simply made it part of the sports package 320is and charged more money to include it in.



Randy

[jaredmac11]

Im still going to try it and I agree this is just a street car and to be perfectly honest Im not sure this car will ever land on the track. It is fun when the rear breaks free a bit, but I havent yet driven with any of these updates. Its been 40+ year old suspension parts with an open diff. Ill still give it a shot.

The reason I got the sway bar is because it was my understanding they came with the LSD from factory and I figured there was a reason for that.

[320iAman]

There is another variable here that cannot be overlooked. The unibody itself after many year becomes twisted and bumped up and down, a frame would generally be less twisted and bumped, so stock goodies will be off slightly, if you put your car on a Kansas City Laser Straightening System it would detect the twist and bumps, I have seen unibodys sliced in half and pieces added and deleted to get the unibody straight again, one thing you get with a straight unibody with all else in specifications, let go of the wheel at speed on a flat road and the car will not veer or drift left or right, another your tires will wear more even, plus other goodies. Knowing the straightness of your unibody in detail one can dial in all factors to get to the best ride more precisely.


Auf Wiedersehen

Randy

[Tom D]

personally i prefer a rear bar and run an adjustable 19mm alpina......throttle lift oversteer rules!

[epmedia]

Im still going to try it and I agree this is just a street car and to be perfectly honest Im not sure this car will ever land on the track. It is fun when the rear breaks free a bit, but I havent yet driven with any of these updates. Its been 40+ year old suspension parts with an open diff. Ill still give it a shot.

The reason I got the sway bar is because it was my understanding they came with the LSD from factory and I figured there was a reason for that.

My '78 has the larger front bar, a rear bar and 3.64 lsd. I'm not sure if the factory did all that, but to my understanding as well, these options were indeed available.

I think you'll get some enjoyment from the rear bar while picking up speed to merge onto some freeways

twisty-freeway-merge.jpg

[jaredmac11]

Haha those are all over Houston too

[gsumzzz]

hitting a bump mid turn makes it even more fun.......