Redesign rear coilover suspension

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flyingwedge
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Redesign rear coilover suspension

Post by flyingwedge » Wed Jan 08, 2014 12:10 pm

I just bought a 1970 Chalenger, converted to weird 3 bar coilover. It has front only pivot traction bars,(round tubing), and a diagonal transverse bar, like a 4 bar coilover would use. I "think" easiest way to un-dork, is remove diagonal bar and use as a panhard bar ? I'm looking for minimal changing, with maximum improvement. Car will see about 1% strip duty , 2% track days,and remainder street use. I will likely convert fron suspension to tube SLA with coilovers. Car currently has a 6 point roll bar and subframe connectors. Building a 540" wedge,700-800hp,manual shift TF, 4.56's in rear, mini tubbed. Suggestions ? Thanks :?:

Brian P
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Re: Redesign rear coilover suspension

Post by Brian P » Fri Jan 10, 2014 10:50 pm

What do you mean by "front only pivot traction bars"?

Do you really mean "lower trailing links" and if so, what's taking up the torque reaction in the axle-wrap direction? Does the design properly allow for one-wheel bump without binding?

There are many ways to locate an axle, and pictures would definitely help.

A lot of drag-racing suspensions won't work properly in cornering or on bumpy surfaces ... doesn't imply that they are bad for their intended purpose, but only that they might not work well for something else ...

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Re: Redesign rear coilover suspension

Post by MadBill » Sun Jan 12, 2014 1:15 pm

One of the better compromises for a road race solid axle is 2 lower trailing links, one (offset to the right) upper and a Panhard bar or Watts link for lateral location. Triangulating the lowers would achieve the same end, but with less lateral stiffness and ease of adjusting the roll center height.
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Re: Redesign rear coilover suspension

Post by flyingwedge » Tue Jan 14, 2014 5:26 pm

Ok, It looks like correct term is "ladder bars". I shall investigate if 2 rear bushings ea./etc., shall allow enough lateral movement, without binding. Basic parts look similar to Competition Engineering kit, without the replacement frame tubes. Diagonal bar "binds" on RE. housing, at static ride height. I would like to re-use diagonal, as a conventional panhard bar. I suspect I want to change IC at front ladder bar pivots, to tune rear bite ? Thanks, flyingwedge. :)

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Re: Redesign rear coilover suspension

Post by Brian P » Tue Jan 14, 2014 9:48 pm

What you're seeing appears to be a more-or-less conventional way to do that style of suspension. Is it like this?

http://www.jimmeyerracing.com/images/ga ... ars-lg.jpg

The advantage of a diagonal like that, is that in a two-wheel-bump situation, the whole assembly pivots around the front pivot centerline and there is no side-pull as there would be with a panhard swinging in an arc. Of course, whether that's really an issue or not is open to question. If the diagonal hits the axle housing or drive shaft ... obviously, somebody improperly designed something.

The bad thing about ladder bars in general is that the suspension will bind in one-wheel-bump or body roll, because any difference between right and left suspension movement can only be taken up by the bushings and the flex of the various components. It's almost like having an extremely stiff antiroll bar. It is essentially a drag-race suspension. Changing the diagonal to a panhard won't solve this.

A google search reveals a few articles about using ladder-bar suspensions on the street.

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Re: Redesign rear coilover suspension

Post by Brian P » Tue Jan 14, 2014 10:05 pm

One other small thing. Right now, if you look at the top view of the car, the ladder bars are probably (almost) parallel. If you bring the front pivot points closer to the middle of the car - as close as you can without hitting the drive shaft! - AND you use compliant bushings at the chassis-end pivot points, AND you use a panhard rod (ideally, horizontal at ride height and as long as possible), it essentially converts your "ladder bar" suspension which doesn't work in corners, to a "truck arm" suspension which does work ... every NASCAR uses that rear suspension design.

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Re: Redesign rear coilover suspension

Post by flyingwedge » Wed Jan 15, 2014 11:21 am

Thanks Brian, Similar to your picture, but more cheesy. I like the idea of a long panhard,(less lateral arc), that can be tuned for lateral bite. Raising/lowering the front pivots, IC, will help tune the forward bite ? More of a trick, may be balancing front/rear, for corner burning. Cheers, flyingwedge. :)

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