Swaybar pre-load question
Thread Starter
Melting Slicks
Joined: Jun 2012
Posts: 3,163
Likes: 6
From: Oceanside California
Swaybar pre-load question
I just installed a Pfadt Heavy rate rear bar. As I understand it, the endlinks need to be adjusted so that they go in easily with the suspension loaded. This would make it so that there is no load on the bar as it sits correct?
I am hearing a lot of clunking as I drive now. I am pretty sure that its just the fact that the heavy rate is not meant for street driving, nor does it help that I have it set to the stiffest setting. But Im getting the car dialed in for a drag race soon so Im leaving it like this for now.
Heres the odd part. When I first installed it, I forgot to remove pre-load by setting the endlinks with the suspension loaded. I set it while the rear was jacked up, then lowered and went for a test drive. After I loosened them and readjusted to remove pre-load the car felt less stable.. Shouldnt I have got better performance after setting them correctly? I mean very noticeably more sway after removing the pre-load..
Any thoughts?
I am hearing a lot of clunking as I drive now. I am pretty sure that its just the fact that the heavy rate is not meant for street driving, nor does it help that I have it set to the stiffest setting. But Im getting the car dialed in for a drag race soon so Im leaving it like this for now.
Heres the odd part. When I first installed it, I forgot to remove pre-load by setting the endlinks with the suspension loaded. I set it while the rear was jacked up, then lowered and went for a test drive. After I loosened them and readjusted to remove pre-load the car felt less stable.. Shouldnt I have got better performance after setting them correctly? I mean very noticeably more sway after removing the pre-load..
Any thoughts?
Race Director
Joined: May 2005
Posts: 15,960
Likes: 21
From: West Norriton PA
St. Jude Donor '08
My guess is that you still have a pre-load on the bars. I would disconnect the links and drive around a bit until the car settles down and then drive in up on some ramps or a 4 post lift and re-adjust the end links so that there is no pre-load on them.
Also your sway bar should move freely when the links are disconnected. I know when I installed the Pfadt bars, I had to shim the brackets out with washers.
Also your sway bar should move freely when the links are disconnected. I know when I installed the Pfadt bars, I had to shim the brackets out with washers.
Melting Slicks
Joined: Apr 2004
Posts: 2,301
Likes: 199
From: Valencia CA
The preload just determines how quickly the bar adds to the stiffness of the suspension. Nothing wrong with running preload.
The clunking may be the play in the bar assembly and end links from not having preload.
The clunking may be the play in the bar assembly and end links from not having preload.
Le Mans Master
Joined: Jun 2009
Posts: 6,528
Likes: 752
From: South Dakota
Maybe I am missing something, but I thought the only preload was for side to side.
The bar itself can rotate in the bushings. The way the sway bar works is when one side suspension moves, it loads the way bar to put pressure on the other side to keep the sides level. If both sides move then the bar just rotates in the bushings and no side to side loading/unloading occurs. So any "preload" if done evenly on both sides only changes the position of the bar in the bushings without any torsional loading on the bar.
In circle track racing we preloaded the sway bar side to side since we were trying to set the car for one direction turning only, but on a street or autocross/road race car they should be set evenly side to side to help turn in either direction.
If there are adjustable end links, they should be set so that they are loose at a normal loaded position, not for preloading purpose, but to make sure the bar is set (centered rotationally) in the bushings so that it can have full rotational travel in both directions .
The bar itself can rotate in the bushings. The way the sway bar works is when one side suspension moves, it loads the way bar to put pressure on the other side to keep the sides level. If both sides move then the bar just rotates in the bushings and no side to side loading/unloading occurs. So any "preload" if done evenly on both sides only changes the position of the bar in the bushings without any torsional loading on the bar.
In circle track racing we preloaded the sway bar side to side since we were trying to set the car for one direction turning only, but on a street or autocross/road race car they should be set evenly side to side to help turn in either direction.
If there are adjustable end links, they should be set so that they are loose at a normal loaded position, not for preloading purpose, but to make sure the bar is set (centered rotationally) in the bushings so that it can have full rotational travel in both directions .
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Maybe I am missing something, but I thought the only preload was for side to side.
The bar itself can rotate in the bushings. The way the sway bar works is when one side suspension moves, it loads the way bar to put pressure on the other side to keep the sides level. If both sides move then the bar just rotates in the bushings and no side to side loading/unloading occurs. So any "preload" if done evenly on both sides only changes the position of the bar in the bushings without any torsional loading on the bar.
In circle track racing we preloaded the sway bar side to side since we were trying to set the car for one direction turning only, but on a street or autocross/road race car they should be set evenly side to side to help turn in either direction.
If there are adjustable end links, they should be set so that they are loose at a normal loaded position, not for preloading purpose, but to make sure the bar is set (centered rotationally) in the bushings so that it can have full rotational travel in both directions .
The bar itself can rotate in the bushings. The way the sway bar works is when one side suspension moves, it loads the way bar to put pressure on the other side to keep the sides level. If both sides move then the bar just rotates in the bushings and no side to side loading/unloading occurs. So any "preload" if done evenly on both sides only changes the position of the bar in the bushings without any torsional loading on the bar.
In circle track racing we preloaded the sway bar side to side since we were trying to set the car for one direction turning only, but on a street or autocross/road race car they should be set evenly side to side to help turn in either direction.
If there are adjustable end links, they should be set so that they are loose at a normal loaded position, not for preloading purpose, but to make sure the bar is set (centered rotationally) in the bushings so that it can have full rotational travel in both directions .
100% Correct.BC
Thread Starter
Melting Slicks
Joined: Jun 2012
Posts: 3,163
Likes: 6
From: Oceanside California
I would be very interested in learning about this stuff. I have never had a tunable setup before. How would you know what to pre-load the bar too?
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Melting Slicks
Joined: Aug 2004
Posts: 3,003
Likes: 89
From: Indy IN
In these cars, since you can jack weights with the spring adjustment screws on each corner of the car there is no reason to preload the bar, but lots of folks do that anyway because that's the way it is done on a lot of other cars.
Thread Starter
Melting Slicks
Joined: Jun 2012
Posts: 3,163
Likes: 6
From: Oceanside California
You put the car on a set of scales and measure wheel weights. You would like the wheel weights in a car with independent suspension to be equal in the back for drag racing. For road racing you want the corner cross weights to be equal to insure the car is balanced and handles the same (doesn't push going one way or is tail happy going the other). In a car that doesn't have adjustable spring perches (like our cars have) you can use the rear bar to jack weight from side to side and equal out the wheel weights.
In these cars, since you can jack weights with the spring adjustment screws on each corner of the car there is no reason to preload the bar, but lots of folks do that anyway because that's the way it is done on a lot of other cars.
In these cars, since you can jack weights with the spring adjustment screws on each corner of the car there is no reason to preload the bar, but lots of folks do that anyway because that's the way it is done on a lot of other cars.
Le Mans Master
Joined: Jun 2009
Posts: 6,528
Likes: 752
From: South Dakota
But doing it with the spring adjustments would require an alignment every time right?... The bar wouldn't change the alignment, only weight on a particular side? Dont get me wrong, if thats the way to do it, Im interested and will look into it. I do have a set of Pfadt's drag specific coilovers on the way too. I'll get much more into all this tuning as I get better parts on the car.
However, if you change the height of the car by spring adjustments or loading one side with the sway bar, the height difference may make a slight change to the alignment. I am not sure how much change they would make or if they are even enough difference to require a new alignment.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
If you alter the rear ride height ANY up or down, it will change the front caster setting.
Changing the overall ride height also affects the alignment camber setting.. So, if you change the spring on one side, you will change caster and or camber on that side.
Bill
Changing the overall ride height also affects the alignment camber setting.. So, if you change the spring on one side, you will change caster and or camber on that side.
Bill
Race Director
Joined: Apr 2007
Posts: 11,152
Likes: 890
From: South Western Ontario
I read about a small bar adjustment making a huge difference in the car handling and it makes me suspect you have some other issue going on.
Either bar or spring adjustments can change the ride height a bit which can affect alignment. It won't be much of a change though if you hardly move it.
Either bar or spring adjustments can change the ride height a bit which can affect alignment. It won't be much of a change though if you hardly move it.
Thread Starter
Melting Slicks
Joined: Jun 2012
Posts: 3,163
Likes: 6
From: Oceanside California
I messed around with adjusting it after a few different drives now. It seems to be better now. I think I am noticing the difference between the front and rear the most. The rear is a heavy rate set on max, and the front is an Eibach non-adjustable. Better than stock I suppose... Just dont want to drop all that money for the front one now!