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Derlin Strut rod bushing?

Posted By: astjp2

Derlin Strut rod bushing? - 12/07/20 03:02 PM

has anyone looked at modifying this mustang strut rod bushing? Its a monoball made from Derlin. A couple of AMX guys seemed to make them work with a little modification. It seems like it might be interesting. Tim

https://opentrackerracing.com/product/racing-strut-rod-bushing-set-1967-1973-mustang/

Attached picture JDs-photos-038.jpg
Posted By: Sniper

Re: Derlin Strut rod bushing? - 12/07/20 03:11 PM

Why not weld up a ball joint sleeve on the K member and use a ball joint instead? Just center the ball up foore and aft in the hole.

The K772 style is available in many heights as well as rebuildable and are very popular in racing.
Posted By: astjp2

Re: Derlin Strut rod bushing? - 12/07/20 04:17 PM

I looked at that, and I found that the hole was too small and ball joints can wear out fast if they get crud in them...maybe a rack and pinion tie rod end?
Posted By: jcc

Re: Derlin Strut rod bushing? - 12/07/20 05:30 PM

When this topic is discussed, not often is it mentioned, what is choice of LCA in play. Meaning, the LCA and the strut are in slightly conflicting arcs, so if both are highly restrained, something has to give or we have bind. The LCA is an easy upgrade for better control and IMO offers real benefits. The Strut upgrade is more complicated, and not sure the benefits are as significant, and if both our chosen, it might make makes worse as bind increases thru greater arcs movement. I sometimes wonder if just another case of monkey see, ......... but then I'm just an alleged liberal arts major......... grin
Posted By: TC@HP2

Re: Derlin Strut rod bushing? - 12/09/20 03:55 PM

This is the problem with a strut suspension as the arc of the control arm will create an effective shortening the strut arm as travel increases. Not ideal but certainly livable if you are running on smooth surfaces without a lot of suspension travel. On something like a dirt track racer, it could become more problematic unless the toe changes are measured and correspond to a desired angle.

The strut bushing being compressed under braking creates toe changes, which can make corner entry feel unstable as the car pitches forward, steering angle increases, and then toe takes you out of the line or requires excessive angle in the steering wheel (all of which will slow you down). A poly or delrin bushing would certainly reduce this impact. However, rubber bushings create less arc conflict through suspension travel as its more compliant and will exert less pull on the control arm. Installing delrin/poly only the backside and putting rubber on the front side might be an alternative to minimize braking changes but allowing less pull on control arm travel. Never tried it or modeled it, just thinking out loud.

I've thought about suing a ball joint in this position as well. You would need to weld in a sleeve to allow the mopar screw in style to live here. Other option is a chevy bolt in style. Of course you now need a threaded strut rod to bridge the gap and a solid, tapered and tapped end for the arm side.
Posted By: jcc

Re: Derlin Strut rod bushing? - 12/09/20 06:43 PM

All excellent points. My thinking on this issue was, a deciding of lesser of two evils, in that the strut, besides any possible "bind" contribution, mainly ,IMO, as you noted, effects toe under braking, and effects it most when braking heavy, which ideally is in a straight line, so we have a possible equal toe out situation ( which actually might be a toe straight more favorable condition if we started with slight toe in?), not ideal, but livable, and thinking braking starts to decline as steering becomes greater on the corner entry, the effect slowly declines, but LCA deflection (camber) from a "soft" bushing, is a factor under nearly every driving condition, not just braking. What am I missing?
Posted By: TC@HP2

Re: Derlin Strut rod bushing? - 12/10/20 02:14 PM

Not missing anything and agree improvements in lower arm motion are bigger net benefits. Delrin in the lower control arm will provide much greater benefit than it will in the strut arm.

Like you describe, braking should be lessening or done as steering input is added. I'd also say the initial stab at the brakes in corner entry creates more pitch than the gradual roll into throttle creates at corner exit. This is why I thought the firmer bushing on the back of the strut may create less change than on the front. But yes, this is fairly minor in the scheme of things.
Posted By: 6PakBee

Re: Derlin Strut rod bushing? - 12/10/20 03:22 PM

Originally Posted by jcc
When this topic is discussed, not often is it mentioned, what is choice of LCA in play. Meaning, the LCA and the strut are in slightly conflicting arcs, so if both are highly restrained, something has to give or we have bind. The LCA is an easy upgrade for better control and IMO offers real benefits. The Strut upgrade is more complicated, and not sure the benefits are as significant, and if both our chosen, it might make makes worse as bind increases thru greater arcs movement. I sometimes wonder if just another case of monkey see, ......... but then I'm just an alleged liberal arts major......... grin


That's the problem I see with replacing the strut cushions with something that doesn't "give". Sooner or later the Delrin bushing are going to wear to get some freedom of movement or the binding that jcc addresses will cause some other kind of failure.
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