rear suspension

[Dave Severson]

I have noticed on some of the drag car type rear suspensions that a few manufacturers are starting to use a torsion bar and link setup mounted on the frame rails and connected to the rear end housing. It is really nothing more than a rear stabilizer bar with some adjustability built into it.

I am considering a similar set up on the back of the Ranchero in an effort to get the torque to apply an equal amount of hook on both rear tires instead of slightly unloading the left rear. With the car setting on individual wheel scales, I hope to be able to play with the chassis preload, etc.

Any thoughts on the subject would be appreciated. My ultimate goal is to get the car to launch straight and hard and keep both tires hooked throughout the process. I have done this before by preloading the right rear a bit, but should I be able to do the same thing by adjusting this torsion bar to transfer the torque at compression of the coilovers. When the car gets on the big end, will the rear suspension be unloaded enough to still provide good stability???

[The Al Show]

I was wondering how it would handle on the road with one side stiffer than the other but my mind doesn't wonder for long before it starts coming up with answers. My thoghts went to my 56 Packard that had torsion bars on all four corners. It would adjust the ride height automatically when you added or removed weight. It had electric motors that would load or unload the bars. If you could find a rear set of bars and motors from an old Packard and wired them seperatley you could change the load on each side from the drivers seat. You could experiment with different amounts of preload by counting how many seconds the switch is on. It would also allow you to lower both sides for cruising.

I just looked up a diagram I have of the Packard system and there's only one motor that loads and unloads all four bars. You would have to find two "levelizer" motors to make it work and it's hard enough to find one. Maybe there's a modern version of this technology available that could be adapted.

[pro70z28]

Originally posted by Dave Severson
I have noticed on some of the drag car type rear suspensions that a few manufacturers are starting to use a torsion bar and link setup mounted on the frame rails and connected to the rear end housing. It is really nothing more than a rear stabilizer bar with some adjustability built into it.

This is the anti-roll bar I built for my "Z". My shocks are 11" apart on center, so I figured I better stiffen it up a little. I haven't heard of using the anti-roll bar for pre-load. But then, this is a learn as I go project so I dunno fer' sur'. I planned to get the pre-load with the four link. From what I understand, they are very effective. This is usually a race set up. But I made aluminum seal housings on my CNC machine for each end of the anti-roll bar, so I can keep the bushings lubed. Hope that will slow wear???

[pro70z28]

Front view shows the linkage a little beter.

[Dave Severson]

Ok Pro, but for the sake of conversation, could the links on the end of the bar be used for a lateral pre-load?? I'm wondering if a bit of pre-load on the right hand side could be used to get some of the lateral movement out of the car and keep it in the groove as you go down the track?? I will be running 36" ladder bars instead of a 4 link on the car.

[pro70z28]

Originally posted by Dave Severson
Ok Pro, but for the sake of conversation, could the links on the end of the bar be used for a lateral pre-load?? I'm wondering if a bit of pre-load on the right hand side could be used to get some of the lateral movement out of the car and keep it in the groove as you go down the track?? I will be running 36" ladder bars instead of a 4 link on the car.

I suppose it would work. It's all adjustable. I won't know for sure how all this stuff reacts to adjustment til' I get it on the road I guess? I have chassis tuning books to get me started in the right direction, but I'm guessing it will be some book knowledge and mostly trial and error. Do you have adjustable rod ends connecting the ladder bar to the housing? I haven't looked into ladder adjustment. There must be a way to adjust some pre-load into the ladder bars? Dunno fer sur.

[Dave Severson]

Yes, there is an adjustable link on the ladder bars. I use this to "soften" the bite a little on hot days or when on the street with street tires. I am wondering about the lateral loading of the tires by preloading one side of the torsion bar???

[pro70z28]

Originally posted by Dave Severson
Yes, there is an adjustable link on the ladder bars. I use this to "soften" the bite a little on hot days or when on the street with street tires. I am wondering about the lateral loading of the tires by preloading one side of the torsion bar???

I can only go by the book on this since I don't have mine on the road yet. According to the Jerry Bickel chassis tuning book, the rear suspension should be adjusted with the anti-roll bar unhooked then reconnected with NO static tension.
Do you have wheelie bars. They recomend adjusting pre-load into the right wheelie bar to sorta' help supliment the suspension pre-load to stop roll off the line and make the car go straight.
So, I guess the answer to your question is No pre-load on the anti-roll bar. Just make the bar as riggid as possible to stop lateral roll. mine has a slight bit of roll because of the linkage connections. I'm thinking I could adjust the linkage ...still loose ....but to the very end of the "lateral travel" of the bar so it shouldn't roll at all sept. maybe for tire squat and a little suspension give. Time will tell. Freind of mine has a gen 1 camaro that runs mid 8's in 1/4. He has no roll bar. When he leaves the line man that thing twists like a pretzel. Bet he would be faster if he stiffened up the back end with an anti-roll bar.

[brickman]

So, may I ask if everyone in this discussion is for 4 bar or ladder bar rear suspension over leaf spring rear suspensions for high performance driving? Will you have to use a panard bar and how critical would it be for the panard bar to be adjustable?

[pro70z28]

Originally posted by brickman
So, may I ask if everyone in this discussion is for 4 bar or ladder bar rear suspension over leaf spring rear suspensions for high performance driving? Will you have to use a panard bar and how critical would it be for the panard bar to be adjustable?

(My opinion only) I would use leaf ...maybe... if it were a cruiser. A lot of this is personal preference. Only you can decide what ride comfort or lack of it you want.


For racing I am using 4 link. Upside it's more adjustable than ladder bar suspension
The down side is it's more adjustable than ladder bar suspension. So it may be harder to tune. Like I said in the previous post I'm learning as I go, so time will tell if I went the right direction.

I would make the panhard bar adjustable. If you raise or lower the ride height you may need to adjust the rear housing back to center. I would use a panhard bar only if you have room. It should be as close as possible to level at ride height. Don't use a short bar. It will mess up the geometry of the rear suspension and end up pushing and pulling the rear housing back & forth when the car goes over bumps. I am using a track locator because a panhard bar in mine could only be about 12-14 inches long. That wouldn't work toooo good.

[Dave Severson]

Bickel's cars definitely work good, guess that ends the wondering. Thanks for the reference, Pro. Guess I will just go back to doing it the way I always have.

Hey Brick, leaf springs would be a better ride on a cruizer that a four bar or ladder bar, but the hook would not be as good with the leafs.