Rear Suspension Help

[69fbodyproject]

For all of you people running 3 link rear suspensions, I am wondering how you determined the lenght of your bars and angles for the geometry. I am still mocking up the body on the frame rack, but we are starting to figure out where suspension mounting points are going to be and how we are going to package this suspension in the chassis.

[MrQuick]

for some its packaging, for some its geometry for others its a known ratio.

You can experiment with the lengths here.

compliments of member Terryr

http://mysite.verizon.net/triaged/fi...kV1.0bBETA.zip save on your hard drive.

[Norm Peterson]

The angles are what determine the geometry. This includes the PHB @ centerline or Watts link main pivot height. Picking appropriate targets for anti-squat and roll steer percentages gets you started.

The lengths determine how fast the geometry changes as the suspension moves. Longer = slower changes = generally better = tougher to make fit. I've heard that having the upper about 70% as long as the lowers is a good place to be, but there's a good bit of room from there if it's a mainly street driven car that you're building (the new Mustang UCA is barely over 45% of the LCA length). FWIW, the UCA:LCA length ratio affects the anti-squat rate of change but does not affect roll steer.

Getting it (and whatever additional structure is needed to carry the link loads) to fit will depend on whether you're going to cut the car up to fit the new suspension in without compromising the geometry at all, if you're willing to give up geometry and/or link length to fit up to the existing chassis with minimal change there, or if you'll compromise all three (link angles, link lengths, amount of chassis rework) to end up with something in between.




Norm

[69fbodyproject]

Since I am working with a truck, I have all the room from the back of the cab, back to the centerline of the diff. We are going to be using a Watts link. Looking for imput on what type of bar lengths I should be looking at. As for cutting the frame, we are fabricating our own so that is not a concern

[BillyShope]

If you're interested in also cancelling driveshaft torque effects, see Pages 18 and 40 of my site:
http://www.racetec.cc/shope

[iou1choke]

Since it sounds like you are looking for a measurement to get you started, why not just extend them up to the back of your cab? Measure that length and figure out what 70% of that length is.... that will determine your upper bar length. Then make sure you have clearance for the upper bar through-out travel. If you do, then start playing w/ your geometry, mounting points and/or frame design. You have lots of freedom w/ trucks to do it right and can end up having a fairly neutral feeling link suspension IMO.