Please explain rear sway bar for drag racing
01-01-2015, 09:22 AM
#1
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Please explain rear sway bar for drag racing Im currently tearing down my IRS suspension and its been some debate lately on whats causing my car spring back up after squatting to launch. Basically the car squats fast, but the rear springs back up so fast that traction is lost almost instantly. We have focused so much on coilovers and stiffness that we haven't looked much into the fat rear sway bar and its adjustability.
Here is what we know or think we know: the huge rear sway bar sorta acts like a live axle when the rear is squatting. Thats it really it.... other than the 3 holes for adjustment we know nothing else about how this is suppose to work. Even the 3 holes which says its for "stiffness" i don't fully understand. It comes with adjustable end links which are basically not being used in my opinion.
Anyone know much about them and where a good starting point for adjusting and how to adjust?
Any links to explain this?
(the pics show the stock shocks and springs, this was only for moving the car from place to place to have other work done)
Here is what we know or think we know: the huge rear sway bar sorta acts like a live axle when the rear is squatting. Thats it really it.... other than the 3 holes for adjustment we know nothing else about how this is suppose to work. Even the 3 holes which says its for "stiffness" i don't fully understand. It comes with adjustable end links which are basically not being used in my opinion.
Anyone know much about them and where a good starting point for adjusting and how to adjust?
Any links to explain this?
(the pics show the stock shocks and springs, this was only for moving the car from place to place to have other work done)
01-01-2015, 09:35 AM
#2
The anti rollbar is to prevent body roll on launch. You need to hook the link up on the driver side at whatever length you choose. Then at race weight, with the chassis loaded, on the tires, on level ground, with driver in the seat, adjust the passenger side link to line up with the anti rollbar hole until the bolt slides through easy. This is set neutral. Then extend the passenger link(make longer) about 1/6 of a turn. This should be a good starting point. If the body still rolls on launch keep making the passenger link longer until the car leaves flat.
The furthest hole out on the anti rollbar is the weakest setting. The setting it appears to have been in is the stiffest.
Your problem as you describe sounds like the shocks are not controlling the chassis movement. It sounds like you need to slow the squat down and the rebound so it won't unload.
The furthest hole out on the anti rollbar is the weakest setting. The setting it appears to have been in is the stiffest.
Your problem as you describe sounds like the shocks are not controlling the chassis movement. It sounds like you need to slow the squat down and the rebound so it won't unload.
01-01-2015, 05:14 PM
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The anti rollbar is to prevent body roll on launch. You need to hook the link up on the driver side at whatever length you choose. Then at race weight, with the chassis loaded, on the tires, on level ground, with driver in the seat, adjust the passenger side link to line up with the anti rollbar hole until the bolt slides through easy. This is set neutral. Then extend the passenger link(make longer) about 1/6 of a turn. This should be a good starting point. If the body still rolls on launch keep making the passenger link longer until the car leaves flat.
The furthest hole out on the anti rollbar is the weakest setting. The setting it appears to have been in is the stiffest.
Your problem as you describe sounds like the shocks are not controlling the chassis movement. It sounds like you need to slow the squat down and the rebound so it won't unload.
The furthest hole out on the anti rollbar is the weakest setting. The setting it appears to have been in is the stiffest.
Your problem as you describe sounds like the shocks are not controlling the chassis movement. It sounds like you need to slow the squat down and the rebound so it won't unload.
Makes sense with the holes, but what i also don't understand is the orange brackets you see in the pics also. They can be adjusted up/down and mine has always been set on level/parallel with the ground. What happens if i point them almost up? Ive seen this on some vettes at the track with IRS, but they also hard a much more beefy rear end then what ive got.
I plan to remove the springs to simulate launch then align from there as far as toe, camber goes. Im assuming this will give me the best starting point for contact patch with the tires and track. Sound like it would work?
01-01-2015, 05:26 PM
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Yes it is and has been almost fixed with some coilovers that i use to run. I put the stock ones back on in these pics because the ones i had were more for road course than drag so sold them. Im trying to decide which brand to go with now
01-03-2015, 01:02 PM
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Why do we adjust the passenger side first?
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01-03-2015, 03:24 PM
#9
It's not a matter of adjusting the passenger side first,it's a matter of adjusting one side ONLY. Lengthening the passenger side puts a preload on the sway bar and that preload is trying to raise the passenger's body side upward and pull the driver's body side downward.
01-03-2015, 03:52 PM
#10
It's not a matter of adjusting the passenger side first,it's a matter of adjusting one side ONLY. Lengthening the passenger side puts a preload on the sway bar and that preload is trying to raise the passenger's body side upward and pull the driver's body side downward.
01-05-2015, 10:59 PM
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For rear alignment my plan is to take off the springs to simulate squat and align the IRS that way. Should the sway bar be hooked up then or do this with springs in the car with no squat?
01-06-2015, 01:46 PM
#13
From what you are describing, anything you adjust with the rear sway bar will not help. The rear sway (or anti-roll) will only reduce the right rear squatting harder than the left rear. You need a good double adjustable shock that will allow you to stiffen the rebound compression. Stiffening up compression will help as well, as it will keep the car from squatting so much to begin with. Being able to tighten the rebound will slow how quickly the car springs back up from a squat condition
01-06-2015, 04:28 PM
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looking into this thread to much. I know for 100% that there is a coilover issue and I address that in the original post as well as others.
What I am talking about here is the rear sway bar and how it operates for drag use. Just trying to get a basic understanding of how the rear sway works and how to adjust correctly.
The rebound and compression for both front and rear has been realized and is being address, just trying to figure out which brand to use, travel length and spring rates.
Thanks
What I am talking about here is the rear sway bar and how it operates for drag use. Just trying to get a basic understanding of how the rear sway works and how to adjust correctly.
The rebound and compression for both front and rear has been realized and is being address, just trying to figure out which brand to use, travel length and spring rates.
Thanks
01-06-2015, 04:53 PM
#15
The only adjustment to a bar is for setting the endlink lengths once installed, and if the bar has multiple end link locations for changing rate. This is determined by how you are using the car. If you are drag racing and not using a front sway bar, you will want the rear bar as stiff as possible to prevent any side to side transfer. This would mean mounting the end links in the position closest to the main bar. For street use, you may want it out on the farthest out position to not bind the rear suspension. Also make sure that witht he suspension loaded that the endlinks "free float" and do not have preload on one side which can cause the car to leave uneven. Otherwise, the bar just kinda sits there and does its thing.
01-06-2015, 06:08 PM
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The only adjustment to a bar is for setting the endlink lengths once installed, and if the bar has multiple end link locations for changing rate. This is determined by how you are using the car. If you are drag racing and not using a front sway bar, you will want the rear bar as stiff as possible to prevent any side to side transfer. This would mean mounting the end links in the position closest to the main bar. For street use, you may want it out on the farthest out position to not bind the rear suspension. Also make sure that witht he suspension loaded that the endlinks "free float" and do not have preload on one side which can cause the car to leave uneven. Otherwise, the bar just kinda sits there and does its thing.