rear suspension design help needed

[wedged]

If i keep the lower parallel to the ground, then i would need a steeper angle on the upper bar. i think.

[Bryce]

Originally Posted by wedged

If i keep the lower parallel to the ground, then i would need a steeper angle on the upper bar. i think.

Yes, if you wanted a higher A/S. For a street car build it to 50 to 100% and make it adjustable. For a drag car I would build it from 90 to 150%. Leaf spring cars have well over 100% but have wheel hop issues, where they cant put the power down. My 65 drag mustang has leafs and slapper bars. I lauch with the front wheels off the ground and I only have 300 hp.

[wedged]

I just spent some time messing with the CAD drawing. I dropped the upper forward mount point a bit and ended up with the instant center at 50". I guesstimated where the center of gravity would be, then drew the anti squat line. What resulted was interesting. The instant center was directly on the 100% line.

Then i went over to the mocked up truck and fired up the FARO ... I wish. I grabbed a tape and held in place to see about where the front pivots points would be. The upper would be outside of the inner edge of the rear tires, making the frame kind of interesting. It would either need to stay low and pass under the upper bar or go really high over the bar. If I shortened the upper bar to about 18" OAL, it could land on the frame rail with the frame a width that would fit between the tires. Of course the lower bar would then be about 20" long. I'm going to think this over a bit before I make a decision on what way to go.

[64pontiac]

Not that I know as much as some on suspension design, but one thing I have found is that IF you have to go with a shorter upper link, you can overcome crazy pinion angle changes and binding by making the attachment point on the housing farther back from the axle centerline than the lowers. It seems when I am playing around with suspension worksheets that a similar ratio as the arm length helps. My 3 link on my 64 has a super short upper link, but is mounted farther back from axle centerline and I have NO pinion angle change over the whole sweep, and Im on bags. I also punched in everythign into the suspension calculator, and I still have acceptable antisquat and roll centers, which are all adjustable.

If you are going for Air ride later, and have a narrow frame, huge rollers, and tight fender clearance stay away from a panhard if at all possible. you will probably touch the tire to the fender on full air-out otherwise.

A watts linkage or sliding wishbone are ideal, as a triangulated 4 link works great for coilovers but tends to bind on air ride systems.

I know you probably have figured everything out, but just wanted to chip in my half cent.