New rear suspension

[TRoadster]

Here is my new and improved 3 link racing inspired rear suspension. I had to cut off the rear shock mounts in order to position the bottom mounts on the rear end so I have to order a new set from Speedway but other than that and some more cone spacers(only had four) she back to a roller. I'll remount the engine and transmission as soon as I get the tubing for the new transmission crossmember and I'll be ready for the body installation.

 

[old round fart]

Lookin' good! Keep up the good work and you'll get there!

 

[LumenAl]

Here is my new and improved 3 link racing inspired rear suspension. ...

Please don't take this wrong... I truly want to know why you went from a 4 link (is that what you had?) to a 3 link... I'm trying to understand (meaning learn) the benefit of one design over the other...

 

[TRoadster]

Actually, I was running a pair of mid 30's ford rear radius rods before. They bolted to a mounted welded to the housing from the bottom with two 1/2" bolts. If I had been running a ford torque tube then there would not have been any problem with that set up. But I learned later with an open driveshaft, the torque acting on the housing causes the older ford rods to break at the mounts. This of course is not good....having your rearend twist out from underneath your car. I like 4 link rear suspension, but on the track. 4 link still has the tendency to bind on the road. The binding accrues when one side lifts up.(Look up on the web) The 3 link does not bind. The lower two links are free to move up and down. The upper link keeps the housing in position. Road racecars have used this suspension for a while because its easy to set up, simple in design and light weight. I just wanted something different. The three main rear suspension on buckets are 4 link, ladder bar/radius rod and independent.


One thing about the old ford radius rods. I read on another forum that they didn't allow enough up and down movement on the rearend. I can say for a fact that my old suspension was not that way. With the rear half of the frame lifted off the rear spring, I could jack either side of the housing at the tires five inches off the ground and the other tire was firmly planted. If you try this with your suspension and the opposite tire becomes light or lifts off the ground, then you have a binding problem.

 

[LumenAl]

I got it... I can definitely see the advantage of the 3 or 4 link over the radius rods, but now that you explain it, I can see where the 3 link would allow for more movement up and down with less binding on the axle.

 

[LKE]

... 4 link still has the tendency to bind on the road. The binding accrues when one side lifts up.(Look up on the web) ...

... I could jack either side of the housing at the tires five inches off the ground and the other tire was firmly planted. If you try this with your suspension and the opposite tire becomes light or lifts off the ground, then you have a binding problem.

If your four link is built right, it will articulate a long way before binding. easily more than a street car needs. Here is a pic of a car I am building now, with a triangulated four link. That wheel is 14" off the ground, and the chassis still dead flat.

 

[TRoadster]

Triangulated four link is better than parallel 4 link which is more common on t buckets. As you know, triangulating 4 link does not need a panhard or watts link to center the rearend.

 

[LKE]

Even a parallel four bar will give all the articulation a street car needs. The picture above is a T with speedway motors parallel four bar front end kit. That axle is tilted 11.4 degrees. making one hub 12.125" higher that the other. And I stopped there only because the axle was about to hit the front spring perch. And I didn't want to chip the paint. A properly built parallel four bar does not bind. In fact I think it is the best choice for a street driven car. That is why most every chassis supplier uses them. The only reason I use triangulated four links on the rear is to get away from the panhard bar, or complexity of a watts link. On most cars it wouldn't matter, but with the air ride I sometimes use, the 8" of suspension movement combined with the short panhard that fits under a T, shifts the axle sideways to far.
So whoever told you a parallel four link binds up, lied to you. I hope he told you the truth about your three link

 

[LumenAl]

At the risk of total embasement... I dream of movements like this!

 

[donsrods]

Boy, that is a pretty blue.

Don

 

[TRoadster]

LKE. I like your picture. I'm running a similar set up on the front of my car. Question. What type of rod ends do you have on the frame? The reason I ask is because if you notice from your picture, you see the front rod ends are not allowing much movement. It's the rear rod ends that are allowing the front to tilt. I've seen pictures where both front and back rod ends are the bushing type. This I would believe would be ok if one or both ends were urethane. But some rod ends that are nylon which does give as much as urethane. Minimum give means binding. Correct? Anyway, there is a difference between how a front end 4 bar and a rear end parallel 4 bar react since the rear has torque for the engine reacting on it and the front just more or less moves with the road. Of course I could be wrong but I would need to se something to change my mind. One further thing. You have a 500lb engine and tranny sitting on your frame. A better test would be to remove the enging/transmission and retest. That will show if or not if there is a problem. I remember someone a while back with a picture on the NTBA forum doing the samething as you but without any weight on the frame.