MYRX

I have read that when installing sway bars, one can improve the handling by placing a washer on the bolt between the sway bar bracket and the frame. Is there truth to this? I am not a suspension set-up expert so I really don't quite understand the reason behind this. If there is truth to this, then why don't many OEM suggest this idea with their installation instructions? Can someone confirm and explain.

ryan0

when going to a larger bar, sometimes the OEM bushings grab too tightly.

you put the washers in to space out the clamp, so it doesnt put as much pressure on the bar, and lets it move freely.

ZR1 MK

All bars should have the correct size bushing.
Ive shimmed the bars to remove preload. In my case, due to corner weight adjustment.

Solofast

Changing swaybar bushing stiffness is a way of fine tuning roll stiffness and tuning to your personal driving style. You can do it with the hardness of the bushings, or make very small adjustments by increasing or decreasing the preload on rubber bushings.

It isn't a matter of making it better, it's more a fine tuning trick to be used when the car is close to where you want it to be, but where, for instance, going to a different bar would be too much of a change and you want just a bit more or less stiffness.

MYRX

So, if I purchased a new larger, stiffer sway bar, that came with the correct poly bushings, are you saying I may not need to grease the bushings and add washers? I guess it is the fine tuning part that I am unsure about. (The installation instructions from the supplier said nothing about adding washers, but I was told this from another HPDE colleage). Perhaps this is a fine tune modification I need to experiment with.

TedDBere

Adding washers will make the bar softer by putting a little "slop" into the system. It's a fine tuning thing that some use. Often times they'll cut a washer and put a little hole with a zip tie through it so they can quickly pull the washers out between runs.

But I have enough trouble seeing the course, let alone judging the need to soften the front bar a small amount. lol.

Solofast

First, the bushings should be correct for the bar and if it is greased properly with the correct bushings it shouldn't bind. If it does bind, then shim it until it moves freely but isn't loose in the bushings.

Shimming any bushings to the point where the bar is loose just makes things sloppy and will mess up your transient response.

Rubber bushings generally have some preload and softening or stiffening the preload can be used if you want to make small changes in stiffness. The technique works better on cars where the bushings are clamped tight by the bar as opposed to the bushings that are designed to slip (like on a C5), but it still works to a lesser extent on a C5.

ryan0

so let me get this straight... youre adjusting swaybar stiffness by 'gripping' the bar with a smooth piece of rubber on a slick painted sway bar, on a 3300 lb car?

ZR1 MK

For all practical purposes, forget the shim technique. You wont be able to tell the difference.

drivinhard

why not? it's so easy if he's already got it apart putting the replacement on.

lube your bushings good, install your bushing brackets, and see if the bar rotates freely in the bushings. if it does, put your end links on. If it's very tight, just shim the brackets till you can rotate freely, and away you go. takes 3 seconds.

(this is probably less of an issue with rubber bushings, especially if they are used/somewhat worn).

expect to re-lube from time to time...

Solofast

NO, THAT'S NOT WHAT I SAID AT ALL

Read what I said....

The reason that it works better on a clamped bar design is that there is a lot more vertical preload and softer rubber to work with. In a "slipper" type bar installation, the rubber is usually harder and there is less deflection in the bushings. It is the vertical deflection in the bushings that you are changing and that are effecting the roll stiffness.

Remember from one wheel to the other, a sway bar system is a series of springs, the bar, the end links, and the bushings are all have a spring rate. Changing any spring constant in the system effects the total roll stiffness. These cars have very stiff sway bars, so changing the attachment stiffness has a bigger effect than on cars with soft bars.

fatbillybob

that happens not because of the bushing but because of the length of the endlinks. That's why you detach and endlink during corner weighting and then passively reconnect it at rideheight.

fatbillybob

I dissagree. The bushing is just a tiny part of the wheel rate a bar can give you. I know where you are going with this and yes you could effect the rate but a very small percentage relative to the bar physics. And if the bushing was so sloppy that the rate changed a lot then you just plain old have the wrong bushing...end of story. Bushing tightness on the bar is not a tuning aid. It is a variable that if you don't control yields unpredictable unreproducible results.

redtopz

Basically the way I look at it is the sway bar bushing bracket was designed to properly clamp over the stock sway bar/bushings. When you go to a bigger bar and associated larger bushings, the clamps do not fit properly. If you try to tighten them over the larger bushings/bar they will deflect and squeeze tightly over the bushing potentially causing binding. A washer(s) can be used as a spacer to achieve close to stock clamping force of the bracket over the larger bar/bushing.

*C7*

BINGO..!!!!!!!

Solofast

Simply not true.

I didn't come up with the idea to fine tune roll stiffness with bushing flexability. It came from a very experienced GM chassis and suspension engineer, who over dinner casually mentioned that they did a lot of fine tuning with bushing stiffness and preload and that because of the high overall stiffness of the bars, that there was a lot of motion in the bushings. I just took that bit of info and ran with it.

Our experience with this is that, if done with moderation, the results are absolutely predictable and reproducible. I've been using it as a tuning tool for over 20 years. It works just fine within the limits described. We often make changes between autocross runs, know what each increment in preload will do and it is very consistent.

Unless you have tried it, you have no concept how effective it is or how well it works.

The limits are about .060 inches of reduced preload in the two front bushing bolts of a c5 z with stock rubber bushings. For a C4, since the preload is greater, you can soften about .100 inches of preload on the two bolts. Using one spacer on one bolt will have about half the effect. On a C4 you can add about .125 inches of preload under the bushing to make it stiffer. These are small changes but if you are looking to get a small increment of change, it works just fine.

rustyguns

wow!

ZR1 MK

Thats what I said.
But shims werent needed when I changed from fixed to adjustable links.

ZR1 MK

All my cars that I changed bar size had proper size bushings supplied. The same bracket gets used. Bushing gets same OD with a larger ID. Everything fits perfect.

MYRX

"All my cars that I changed bar size had proper size bushings supplied. The same bracket gets used. Bushing gets same OD with a larger ID. Everything fits perfect. "


My new bar came as mentioned above, thanks for all of the response. My question has been answered.

Hope to see some of you guys in December at the NASA Rd. Atl event.