Sway bar size suggestions.

[cyrmanj]

Well, finally I got the Bimmerworld sway bars kit and will install them shortly.

Does anyone has pics of the reinforcements already welded to use as a reference?

Any other pointer or guideliness to follow...

Thanks...

P.S.: Looking forward for some track day action on september 29th. :p

[digger]

rather than starting a new thread what size rear bar for 375/525 with front 25mm IE (Hollow) in soft setting for the street?

with current setup iot feels like the rear lags behind the front when travelling at a decent speed with largish steering transient inputs. Odd thing is overall it seems pretty neutral when pushing it on constant radius curve just under transients it feels off

[moatilliatta]

Like the rear is wagging along and sets excessively late when weight was translationed?

[digger]

Like the rear is wagging along and sets excessively late when weight was translationed?

yes, my thoughts are the roll stiffness at the rear is quite a bit softer than the front under transition conditions, but seems ok from a balance perspective at "steady state".

I just want to gauge what others have found works well as far as bar sizes with around the 375/525 or similar stiffness's.

my concern is with a larger bar it may respond better under transition but have a higher tendency to oversteer.

perhaps solid end links will improve transition without affecting ultimate balance as my poly links would be affecting the effective stiffness and the response

[moatilliatta]

Could always disconnect one side and see what you think to rule out bar tuning. Dampers could be getting old

I have no 375/ 525 rate experience .

[digger]

Could always disconnect one side and see what you think to rule out bar tuning. Dampers could be getting old

I have no 375/ 525 rate experience .

i have KONI SA that arent very old, the soft to hard setting does affect things but it is a fairly subtle change.

disconnecting the link on one side may provide useful data if it gets worse then i know i need more.

I'm going to be swapping out the diff and axles, bearings etc in coming months so if was going to do a rear bar its a whole lot easier at this point so was thinking of just going up one (1) size as i have enough front adjustment to compensate the overall balance. its probably worth doing the disconnect first off

[citizen_insane]

I also do not have any experience with those spring rates but when I plug them into my setup sheet, there's a huge difference in ride frequency between front and rear (F = 2.08 Hz, R = 1.8Hz).

In my experience setting up my own car for AutoX and road racing, I found my chassis responded better to similar ride frequency F&R. The suggested setup from Ground Control uses 650lb/in springs and I found that by disconnecting the rear sway completely and increasing the rate to 750lb/in the car felt more predictable and was able to put down power better at corner exit. I'm running a garagistic 22mm front sway bar and the GC custom Koni shocks with extra damping.

My first suggestion would be to increase your rear spring rate to ~650lb/in (let me know if you want my old 650's I think I have them sitting around) to even out the ride frequency before playing with the sways. This of course assumes you have some additional shock to play around with since increasing spring rate means you'll need to increase damping as well.

For reference, my setup is:

• 440/750 Eibach Springs on GC coils & GC valved SA Konis (F = 2.25 Hz, R = 2.15 Hz)
• 22mm Gargistic front sway with adjustable links
• No rear sway
• Ride height set via corner balance (50% cross weight, 53% Front, 47% Rear)
• Rival S 1.5 245's on 15x10 wheels (not sure this matters, but I have a lot of mechanical grip so it may affect handling balance)

[digger]

I also do not have any experience with those spring rates but when I plug them into my setup sheet, there's a huge difference in ride frequency between front and rear (F = 2.08 Hz, R = 1.8Hz).

In my experience setting up my own car for AutoX and road racing, I found my chassis responded better to similar ride frequency F&R. The suggested setup from Ground Control uses 650lb/in springs and I found that by disconnecting the rear sway completely and increasing the rate to 750lb/in the car felt more predictable and was able to put down power better at corner exit. I'm running a garagistic 22mm front sway bar and the GC custom Koni shocks with extra damping.

My first suggestion would be to increase your rear spring rate to ~650lb/in (let me know if you want my old 650's I think I have them sitting around) to even out the ride frequency before playing with the sways. This of course assumes you have some additional shock to play around with since increasing spring rate means you'll need to increase damping as well.

For reference, my setup is:

• 440/750 Eibach Springs on GC coils & GC valved SA Konis (F = 2.25 Hz, R = 2.15 Hz)
• 22mm Gargistic front sway with adjustable links
• No rear sway
• Ride height set via corner balance (50% cross weight, 53% Front, 47% Rear)
• Rival S 1.5 245's on 15x10 wheels (not sure this matters, but I have a lot of mechanical grip so it may affect handling balance)

thanks for your input

one of the reasons i varied from the standard supplied setup 375/475 and ordered the 525 was the FtoR balance seemed off on paper and 525 was a slight step in right direction, i didn't do any calcs. Perhaps the 375/475 that it originally came with is probably based on the large rear bar combis that most sway bar kits come with e.g. 22/20mm etc. I will contact GC and see what the rear shocks are good for i vaguely recall that 700 was the number when i got the different rear spring.

what length are your 650's?

[citizen_insane]

I'm guessing that GC setup their system to work with stock (or slightly larger, but balanced) front and rear sway bars being run, which necessitated a lower than idea rear spring rate. They also probably tuned slightly to the understeer side of neutral since that's where most drivers are most comfortable.

The old rears I have (which came from GC) are 0500.225.0650, so 5" long.

[digger]

Mine are 2.5” x 6” so probably won’t quite fit over the seats . Springs are pretty cheap though.