Starting to Think about a Race Car Sized Rear Sway Bar

[ron@whoosh]

the parts are not cheap but there are a few options available that weren't mentioned

 

[Dialcaliper]

the parts are not cheap but there are a few options available that weren't mentioned

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The DNA adjustable piece is sweet, but only 20mm diameter (smaller than other options), and even the cool design doesn't behave that much differently from the typical unconstrained bar in our application. The Swave piece is pretty cool, but aluminum (which is less "springy" then a steel bar of the same diameter, so that's a bit of a penalty. Its not clear if either could be run in combination with an additional rear bar, as they both seem to block at least some part of where a "typical" rear antisway bar would sit.

@ron@whoosh do you have a size on the Swave bar, and is the center twist bar actually aluminum or just the end pieces? I can't seem to find a diameter anywhere.

 

[WannabeST]

I don't have any rear reinforcement on my car (yet) so please forgive me if this idea doesn't sound possible.
Based on looking at pictures and reading this thread. It seems like the best combo would be the pierce brace, that orange swave and summit bar, and then your choice of rear sway bar. If the sway bar doesn't fit with the orange bar. You could probably make a spacer and use longer bolts. I'm not sure how much of an effect a lower sway bar would have on handling. But this seems like a possibility in my mind.

 

[M-Sport fan]

On a lot of the Swave/Summit parts it is the exact opposite of that (steel end plates/mounts, and aluminum alloy center bar), like on their trunk/inside of hatch floor brace installed on my ride.

I like that Swave/Summit piece since it takes away the least amount of ground clearance of any of the NOT mounted inside of the torsion beam axle braces, and some of the sway bar options.

 

[WannabeST]

A spacer right here on the 2 bolts on each side is where the spacer seems suitable. My assumption is that the only negative to this would be potential ground clearance issues.

 

[Fusion Works]

I unfortunately haven't put video in my car yet. I am so busy getting the car ready to go on track, that I am bustin ass at the last minute to get the car on the trailer and to the track and mostly not forget anything.

When I go to Barber in Nov I hope to be setup for video and some data acquisition. I ran a pathetic 1:50 at Barber during the SCCA Time Trial a couple of weeks ago, car was better than it was in June, but not by much. Still needs more rotation.

I think Woods24/7 has some video if he wants to share them. Here is a pic from the car going through turn 1 at Barber, its a uphill left hander, that is a ton of fun.

 

[Dialcaliper]

I don't have any rear reinforcement on my car (yet) so please forgive me if this idea doesn't sound possible.
Based on looking at pictures and reading this thread. It seems like the best combo would be the pierce brace, that orange swave and summit bar, and then your choice of rear sway bar. If the sway bar doesn't fit with the orange bar. You could probably make a spacer and use longer bolts. I'm not sure how much of an effect a lower sway bar would have on handling. But this seems like a possibility in my mind.

Just to chime in, the kind of roll stiffness Fusionworks is looking for in this thread is appropriate for a track car with heavy downforce (front splitter, maybe rear diffuser) that depend on maintaining ride height to produce said downforce.

If you ever intend to drive your car on the street or anything but a fairly smooth track, and have not fitted serious aero devices to your car, this sort of roll stiffness is not going to provide a benefit, and will simply reduce grip on the rear axle as the suspension is less able to move independently on each side. Ride quality will be terrible (sway bars are usually the worst contributor to this, sometimes even more than stiff springs and dampers)

 

[Dialcaliper]

I am completely happy to swap cars and see what you think. The car isn't as loose as I prefer for a track car. The car is fine for a street car, there is a huge window in comfortable street setups. My car doesn't burn the inside tire off any more. HAHA

You are never going to be running at the speeds and slip angles on the street you are running on the track with hot sticky track tires, aero, and smooth tracks with minimal bumps. I also want maximum durability on the front tires. The "front stiff" setup that most people and OEMs run on street FWD cars is fine for two or three laps. The tires come up quick and the car does pretty well, but if you want a truly fast track/race setup that can lay down consistent laps for a 20 lap race or 20hr race front stiff ain't where its at for a FWD car.

My setup at Barber last month was:
Front Camber -2.25
Front Toe 0
Front Caster 5.5+
Rear camber -2.5
Rear toe .070 out.

Tire pressures end up at 32-34psi front and 34-36 rear.
Front springs 450lbs
Rear springs started the weekend at 550lbs and ended the weekend in the 650lbs range
Eibach rear bar
Stock front bar. (I think it was connected, LOL. I disconnected it in June)
LF 901
RF 899
LR 624
RR 512
Car is not on the bumpstops, its at the factory ride height.

Splitter was 3in off the deck and 5in out the front of the car. Rear Wang angle was reduced from 2deg down to 0 early on Sat.

@Fusion Works I’m kind of wondering if some of your rotation issues stem from, wait for it…not enough front roll stiffness… specifically, the effect that front roll has on your splitter. Your front springs are more than stiff enough, but springs alone don’t control roll very well on this platform - you mentioned that disconnected your front sway bar.

If your splitter is at too steep an angle across the front of the car, you’ll leak air on the inside and choke flow to the outside as it scrapes the track, and lose some of your downforce in the front, leading to a push. If this is the case, simply adding massive rear stiffness to the the rear will just kill rear grip as well and slow you down.

This will be especially the case at speed, and I noticed you mentioned trimming out the rear wing to zero in an attempt to fix it, which leads me to believe you were seeing it more at higher speed. Also if you recently lowered your splitter, it will become even more sensitive to this sort of ride height variation.

Not trying to dissuade you from the sway bar path, but just tossing out some other things to think about, and going back to the “low speed=suspension, high speed=aero” for tuning out understeer/oversteer issues

 

[ron@whoosh]

The DNA adjustable piece is sweet, but only 20mm diameter (smaller than other options), and even the cool design doesn't behave that much differently from the typical unconstrained bar in our application. The Swave piece is pretty cool, but aluminum (which is less "springy" then a steel bar of the same diameter, so that's a bit of a penalty. Its not clear if either could be run in combination with an additional rear bar, as they both seem to block at least some part of where a "typical" rear antisway bar would sit.

@ron@whoosh do you have a size on the Swave bar, and is the center twist bar actually aluminum or just the end pieces? I can't seem to find a diameter anywhere.

the swave rear beam torsion arm rod and brackets are steel

 

[Dialcaliper]

the swave rear beam torsion arm rod and brackets are steel

That makes more sense - the product entry seems to list the whole standard Swave/Summit spiel about everything they make being “aluminum monocoque”, which threw me off.

 

[M-Sport fan]

the Swave rear beam torsion arm rod and brackets are steel

THANK YOU Ron for clarifying this question.

 

[Fusion Works]

Just to chime in, the kind of roll stiffness Fusionworks is looking for in this thread is appropriate for a track car with heavy downforce (front splitter, maybe rear diffuser) that depend on maintaining ride height to produce said downforce.

If you ever intend to drive your car on the street or anything but a fairly smooth track, and have not fitted serious aero devices to your car, this sort of roll stiffness is not going to provide a benefit, and will simply reduce grip on the rear axle as the suspension is less able to move independently on each side. Ride quality will be terrible (sway bars are usually the worst contributor to this, sometimes even more than stiff springs and dampers)

Can concur, ride is pretty terrible. LOL. My own fault, haven't pulled the 450/550 setup off and its pretty brutal on some elevated road way type bumps. Its ok on smooth roads, but it will bounce you pretty hard. HAHA. When I get the Radical out of the way I will pull it in the shop and experiment with pulling the Eibach rear bar, just to test your theory. (Plus I need it for a template)

 

[Dialcaliper]

Can concur, ride is pretty terrible. LOL. My own fault, haven't pulled the 450/550 setup off and its pretty brutal on some elevated road way type bumps. Its ok on smooth roads, but it will bounce you pretty hard. HAHA. When I get the Radical out of the way I will pull it in the shop and experiment with pulling the Eibach rear bar, just to test your theory. (Plus I need it for a template)

Just to clarify, my suggested experiment is specifically to reconnect the FRONT sway bar if it is currently disconnected, (without changing anything else) and test it out with the lowered splitter to see if it has any effect, or if I’m off my rocker. Any changes you make to anything in the rear would not have much of an effect if your understeer is from the front aero misbehaving in front axle roll rather than a strictly “suspension” oversteer/understeer issue.

 

[Fusion Works]

I’m kind of wondering if some of your rotation issues stem from, wait for it…not enough front roll stiffness… specifically, the effect that front roll has on your splitter. Your front springs are more than stiff enough, but springs alone don’t control roll very well on this platform - you mentioned that disconnected your front sway bar.

Two different setups. When I ran Gridlife back in June, I was running 250/250 with 21mm Eibach rear bar, same alignment and Little Wang, splitter was 3in long and 4in off the deck. By the end of the weekend I was out of spring rubbers and resorted to disconnecting the front bar to try and get the car looser. 250lb front springs the car just flops over on that corner, its pretty terrible for track work.

Last event was 5in splitter 3in off the deck, 450/550, 21mm rear bar, stock Front bar connected, same wang, just dialed down 2 deg.

On a strut car, springs will work fine for controlling front roll stiffness, they also don't have the inherent compromises of big sway bars on inside tire lift, thus making the front wheel spin on corner exit.

I am also not running the car that low, its basically stock ride height.

If your splitter is at too steep an angle across the front of the car, you’ll leak air on the inside and choke flow to the outside as it scrapes the track, and lose some of your downforce in the front, leading to a push. If this is the case, simply adding massive rear stiffness to the the rear will just kill rear grip as well and slow you down.

The car doesn't "push" as far as a normal person is concerned, its just not as free as I would like. Its not an aero push as the car is fairly neutral when I over cooked it into turn 1. Was surprised it didn't get backwards, but I just laid on the throttle and thats probably what pulled it out straight.

This will be especially the case at speed, and I noticed you mentioned trimming out the rear wing to zero in an attempt to fix it, which leads me to believe you were seeing it more at higher speed. Also if you recently lowered your splitter, it will become even more sensitive to this sort of ride height variation.

Again, if the car were "freeer" in the slower speed stuff I suspect the high speed is fine. Wing tuning saved me crawling around under the car in 100deg paddock temps. Need to hit RA or NCM to see how it behaves though. My Little Wang is no where near as big as most people's. Its 48in long. I thanks Woods24/7s Big Wang is 72in wide. He has a lot more rear down force.

Not trying to dissuade you from the sway bar path, but just tossing out some other things to think about, and going back to the “low speed=suspension, high speed=aero” for tuning out understeer/oversteer issues

If it don't work, I can cut the bends up and will have some spare 4140. In my past experience, a big bar makes a FWD work better than any other setup. I typically run huge bars on all my race cars and they work well. I built a 1.75x.095 diameter rear bar for an Acura CL, think I have a 1.25 x.095 on my Integras, etc. The bigger the better, within reason.

 

[D1JL]

A spacer right here on the 2 bolts on each side is where the spacer seems suitable. My assumption is that the only negative to this would be potential ground clearance issues.

The spacer was adder to allow the use of the non-ST bar to be used on the FiST.
I provided this fix to Eibach when I bought my FiST and used my non-ST bar on it.
There was never an issue of ground clearance as the bar never hung below the rear wheel rim.

 

[Fusion Works]

The spacer was adder to allow the use of the non-ST bar to be used on the FiST.
I provided this fix to Eibach when I bought my FiST and used my non-ST bar on it.
There was never an issue of ground clearance as the bar never hung below the rear wheel rim.

What was the point of the spacer? I don't think I have that spacer on my car.

 

[D1JL]

What was the point of the spacer? I don't think I have that spacer on my car.

It was needed because of the design/bend of the original non-ST bar did not fit the Twist-Beam of the FiST correctly.
A later new design was then used which included the spacing in the bar.
The newer bar then fit both the FiST and non-ST cars.

 

[Fusion Works]

Weird.

 

[WannabeST]

It was needed because of the design/bend of the original non-ST bar did not fit the Twist-Beam of the FiST correctly.
A later new design was then used which included the spacing in the bar.
The newer bar then fit both the FiST and non-ST cars.

If the spacer has no effect on handling and ground clearance. Shouldn't adding a spacer be a pretty simple solution to just put all 3? With this you could get to the point where rotation may just be down to angle of attack on the wing for adjustment

 

[Fusion Works]

If the spacer has no effect on handling and ground clearance. Shouldn't adding a spacer be a pretty simple solution to just put all 3? With this you could get to the point where rotation may just be down to angle of attack on the wing for adjustment

Not sure I understand your question?