speedway motors boxed rear control arms

[pagrunt]

It's not complaining. Just an explanation for you yourself to make a decision on what is better.

An OEM rubber bushing has enough give in it where it can twist or rotate the control arm with the axle housing. A heim joint and a roto joint can do the same thing.

A poly can Not. The only way it can is when you force it. This is hard on the bolts, mounts and the arm itself, especially if you have "boxed" it.


3 pages later, I'm thinking, nobody gets it so here is a visual to explain.

This👆is one of the reasons why I have the UMI roto/poly arms. They replaced OE arms with all poly. My car will be a street car but still want it to handle the best way possible. Unlike in the video my lowers have the rotos at the axle end, my uppers are at the frame end. Still not sure if Jr.'s ride will get the same set up or stay rubber.

 

[Ernest]

Those roto joint control arms are great.... so you are implying that the roto joints are one sided, since you placed them where you wanted them specifically, arent they on both ends?

 

[pagrunt]

Those roto joint control arms are great.... so you are implying that the roto joints are one sided, since you placed them where you wanted them specifically, arent they on both ends?

For me, my lowers was shipped with the roto joints at the axle end. I opted for the one roto per arm to add some more articulation that poly would ever offer but keeping some sort of (limited) cushion that I wouldn't get from roto joints. Depending on how things go down the road I could go all roto joints. But I have to get it back on the road first. Before I forget, I got the round UMI uppers & lowers.

 

[Rt Jam]

The axle has to be free to tilt. With a roto joint on either end, it can.

A ladder bar car or a 4 triangulated arm car with poly or solid bushings both have the same problem. They can easily swing the axle in an arc but tilt is a no go. Just like a door. Top moves, bottom moves. Left moves, right moves.

 

[scoti]

The axle has to be free to tilt. With a roto joint on either end, it can.

A ladder bar car or a 4 triangulated arm car with poly or solid bushings both have the same problem. They can easily swing the axle in an arc but tilt is a no go. Just like a door. Top moves, bottom moves. Left moves, right moves.

I always understood the C4L (converging four link suspension for those that don't know) as functional; but not functionally good.

The issue stems from the upper links being required to do two jobs (pinion + lateral movement control) as the suspension travels through its range. The OE stamped arms allowed things to work because of their type of construction (we can agree they're flimsy @ best) & those cushy rubber bushings. Boxed Poly bushed arms might work decent for a car that's MAIN focus is straight line performance. Actual 'touring' style driving requires a better selection of parts.

IMHO, the best ones out there that have no bind restrictions are Detroit Speeds Swivel Links or Speedtechs Articulink. Both allow 360° rotation of the opposite ends (w/o changing their overall length). They are also pricey but they're the best options for a car that's going to be driven harder than the typical grocery store or church drive. Behind them would be any of the spherical joint options. These choices offer the best control of the engineered C4L situation.