Effect of rear swaybar on e36

[aeronaut]

Here's a thread from the archives worth reading

http://www.bimmerforums.com/forum/ar.../t-423480.html

Good read.
One quote "I calculated the wheel rate of a 19mm rear sway bar at around 32 lb/in using a motion ratio of 0.45 and an effectiveness of 70% (a guess to account for bushing compliance and other unaccounted-for deflections). That's equivalent to ~70 lb/in of spring (in the stock location)."

That's actually a bit more than I thought it would be. Maybe I'll experiement at next track day and disconnect one end. (I'm currently running 650 springs in the rear). But...I like having the sway bar there to limit droop when I jack one rear tire up.

[=BA=]

I run a huge split without rear swaybar.

900 fronts with stock 22,5mm bar (95 M3)

500 rear springs on coil over which is about equivalent to 1200 lb/in by a quick calc.

[=BA=]

Good read.
One quote "I calculated the wheel rate of a 19mm rear sway bar at around 32 lb/in using a motion ratio of 0.45 and an effectiveness of 70% (a guess to account for bushing compliance and other unaccounted-for deflections). That's equivalent to ~70 lb/in of spring (in the stock location)."

That's actually a bit more than I thought it would be. Maybe I'll experiement at next track day and disconnect one end. (I'm currently running 650 springs in the rear). But...I like having the sway bar there to limit droop when I jack one rear tire up.

Data I have on E36 M3 suggests 40 lb/in (this comes from a report where one of the competitior factories got their hold on a E36 M3 back in the day it just came out, and performed a kinematics and compliance test) also it suggests 80 lb/in for the fronts.

[VRT]

Data I have on E36 M3 suggests 40 lb/in (this comes from a report where one of the competitior factories got their hold on a E36 M3 back in the day it just came out, and performed a kinematics and compliance test) also it suggests 80 lb/in for the fronts.

BA could you post this data or article? I would be interested in reading it

[testify]

The big benefit with removing the rear bar is that the inside rear tire will droop on corner exit instead of lifting, and thus you will have more traction to put power down on exit.

[r0nd3L]

I run a huge split without rear swaybar.

900 fronts with stock 22,5mm bar (95 M3)

500 rear springs on coil over which is about equivalent to 1200 lb/in by a quick calc.

That makes sense. I ran most of the last year season with 800/900 springs and no rear bar. The car, while put power down OK, wanted to lift front wheel so much that it was very hard to drive. I kept putting whole car on 2 wheels! I'm running UUC rear bar on full soft and it's a lot better now, but I feel I could put power down a little earlier. I will experiment with 1000 and 1100 rear springs with no bar and see where that gets me.

[jakermac]

That makes sense. I ran most of the last year season with 800/900 springs and no rear bar. The car, while put power down OK, wanted to lift front wheel so much that it was very hard to drive. I kept putting whole car on 2 wheels! I'm running UUC rear bar on full soft and it's a lot better now, but I feel I could put power down a little earlier. I will experiment with 1000 and 1100 rear springs with no bar and see where that gets me.

I also have this issue with 800/900 and a small front Ground Control sway bar. Before I go back to a rear bar, I'm going to try a larger front bar, and make absolutely sure I have no rear suspension binding/interference.

[=BA=]

I also have this issue with 800/900 and a small front Ground Control sway bar. Before I go back to a rear bar, I'm going to try a larger front bar, and make absolutely sure I have no rear suspension binding/interference.

That will just make it worse.

@ VRT: I would have to look through my files if I still have the original. But I memorized the numbers.

AFAIK original for a 95 M3.

Springs 17 N/mm front 44 N/mm rear.
ARB's 14 N/mm front 7 N/mm rear.

Multiply by 5.709 for lbs/in.

[r0nd3L]

I also have this issue with 800/900 and a small front Ground Control sway bar. Before I go back to a rear bar, I'm going to try a larger front bar, and make absolutely sure I have no rear suspension binding/interference.

Wouldn't that be counter productive? I think the problem is not enough rear roll stiffness with RSB removed compared to the front. Adding more front bar, would make the problem worse.

But, do let us know the results nonetheless.

Btw, I have GC spherical RTABs, GC spherical lower arm, Turner spherical upper control arm bearing and new factory ball joints, suspension moves very freely!

[jakermac]

Wouldn't that be counter productive? I think the problem is not enough rear roll stiffness with RSB removed compared to the front. Adding more front bar, would make the problem worse.

But, do let us know the results nonetheless.

Btw, I have GC spherical RTABs, GC spherical lower arm, Turner spherical upper control arm bearing and new factory ball joints, suspension moves very freely!

A bigger front bar would limit overall body roll which WILL help with inside rear wheel lift. I too have all sphericals in my suspension. I'm not concerned about pivot point binding, but I am about contact in various places in the rear suspension geometry. The upper spring seat centering "nub" on the chassis can make contact with the top of my GC articulated lower spring perches. I have done some careful measuring and "adjustments" so I don't think it's that. I am running 4" tall rear springs, and I know I do not have spring binding. There is 1 place that I have yet to check for contact, and that's between the upper control arm and the trailing arm. Someone recently pointed out to me that they are experiencing contact there and I have not been able to confirm or deny if I have the same contact.

[MINIz guy]

I am running 4" tall rear springs, and I know I do not have spring binding.

Jake, what is your rear ride height at the jack point with 4" springs?

Finally got out more with my E36 this season. 560 lb/in front and 671 lb/in springs in the rear, Hotchkis front bar on soft. With no rear bar, there is a lot of mid-corner and corner exit push, it will also tripod an insane amount on corner exit. With the stock 15mm rear bar, I still get corner exit push but I don't tripod as much. The entire car still rolls a lot with these rates, more than what I think an STX car should.

I want to bump up front rate to 650lbs and then play around with 800-900lb rear springs, all without a rear bar. Should make the car more composed when I'm hucking it around the slaloms, instead of waiting for it to settle before getting back on it.

[JBasham]

My experience is limited, but here it is. I ran stock M3 suspension with and without the rear swaybar, but it was the 325/328 swaybar, not the M3 bar I really couldn't tell the difference at Summit Main. It rolled far more than I liked either way. Since then I have chucked the M3 stuff and I'm off on a different tangent.

[jim13x]

E36 M3 on 200TW Direzzas.

I'm running a GC bar in the front (I think it's the biggest one), Bimmerworld race LCAs, 750lb front and 800 lb rear, no rear bar. I played with 600, 700 and now 800 rear springs with the double-adjustable konis on full stiff, and I think I will try 900lb rear springs next.

It's my second season racing. You could have given me a perfectly setup car a year ago and I would have told you it was too stiff in the rear because I was turning in and not getting on the throttle, inducing oversteer. Now that I've learned to transfer the weight to the rear as soon as I turn in I like the feel of a stiffer rear end.