I'm in the early stages of restoring a 69 roadster. Just got my frame back and currently doing the suspension.

About to reassemble the ft control arms after media blasting & painting, but got to thinking about whether to polish the ends of the control arm shafts to minimize friction between shaft ends and bushing inner sleeves as the suspension moves. I had been assuming thats where the slip was supposwd to happen. . But then what's the logic behind the cited benefits of delrin bushings reducing stiction if the slip is actually between two metal pieces not between delrin and metal?

I'll actually be using rubber bushings in my setup. Im only mentioning delrin as it's what's making me doubt where the slip is supposed to happen.

 

Actually, with stock style rubber bushings, there is no "slip"in the bushing. Once the nuts/ bolts are tightened, the inner sleeve becomes fixed to the shaft, the outer shell is fixed to the arm and the rubber is essential fixed to both. The movement occurs within the rubber itself. That is why it is important to have the car at ride height when you tighten the bushings. This ensures the rubber in its neutral position when suspension is at its normal position.

 

Delrin has less deflection than Rubber and poly and is a better bearing surface than metal bushings.

 

Neither Delrin or Poly will last long on the street as a substitute for rubber bushings due to not only the braking and acceleration force, but the fact that the control arm makes a very slight arc as it moves up and down.......

Jebby

 

Well. That makes sense, and frankly wasn't at all what I was expecting. The part about waiting until car is at ride height / neutral position made this click for me.

Still leaves me wondering about delrin a little, though. In context of it having less deflection than rubber makes me wonder if the reduced deflection would cause reduced control arm arc length and why that would be viewed as a good thing. Wouldn't it just tear up the bushing or limit the suspension from moving across full range motion as designed? Also if delrin is marketed for these bushings as having lower stiction yet control arm bushing movement is all about deflection (stretch) where is the point of friction that delrin is supposed to improve?

 

The Delrin & poly bushings work differently than the rubber ones. The inner and outer sleeves are fixed and the bushing does slide in the sleeves. That is why Delrin works so well, it is as slippery as Teflon, just more rigid. I still grease them, because of the sliding, even tho they say it is not required, it just makes sense to me. The poly is not as slippery and has a deserved reputation for squeeking. The greasing is necessary there, and still may not prevent the squeeking. And I disagree, Delrin does not degenerate with age. My 35 year old Global West Delrin bushings attest to that, and they had serious use in 1000 autocrosses. But a lot of the poly(urethane) bushings do crumble with age, even after a few years, because the plasticizers inside will continue to crosslink over time, it loses its flexibility and gets very brittle, just as old rubber does. And then it crumbles. Teflon and Delrin do not do that. But Teflon is just too soft to use as a bushing, where the Delrin is much firmer.

I endorse the use of Delrin on the front a-arms, where all they do is rotate. I will never use poly because of the squeeking. Poly is fine for sway bars in my opinion. On the rear I would not use poly or delrin on anything that moves in the C3 IRS. Both the trailing arm and the strut rods need 2 angles of freedom, ie: they rotate as well as twist laterally. The "plastic" bushings do not hold up well when continually "flexed/compressed" during the twisting motion. Stick with rubber in the trailing arm, and either rubber or metal heim joints in the struts rods.

 

This is the absolute truth.

Consider this…

Back in the late 1980s-early 1990s, Herb Adam’s (Pontiac Firebird/Trans Am engineer and later VSE fame) did a test with a third generation F body (Camaro I believe), changing out various suspension components and then measuring the “improvement” each change made. One of the changes was to swap out the stock rubber bushings for polyurethane (might have been delrin, but pretty sure it was poly). The change? It was .01g. That’s probably within the margin of error and considering all of the drawbacks of poly or delrin (harsher ride, potential squeaking, accelerated wear/failure), I don’t know why anyone who has actually looked at this area of the suspension would want to use anything other than rubber for a street application.

As always, this is only my opinion, but I’m basing it on what Herb Adam’s discovered during his own testing and years of engineering experience.

Regards,

Stan Falenski

 

Have you considered SPC adjustable UCAs? Take your pick of LCAs. Delrin is great for this application (and famously awful for the trailing arm bushings and strut rods, which have a complex motion).

 

And that also makes sense. Good explanation.

 

Those are pretty nice, but not in the cards for me due to total restoration budget. Thanks for the suggestion.

 

Just going to add that for a number of years VB&P was selling sub par quality poly that people thought was "Energy Suspension" brand however they were not. These poly bushings hardened and crumbled in short order and gave poly a bad name on this forum. I researched the hell out of this both by searching old threads here and reading up on other car performance forums. It seems certain popular car makes like our corvettes suffer from more knock off chinese crap than others. One problem is many corvette part reseller bundle these crap parts into kits people buy thinking they are saving money when rebuilding... This muddies the waters on opinions since people sometimes believe what they want to support thier decisions right or wrong.

You will find lots of conflicting opinions but most agree delrin is not ideal for street applications. delrin is great and has advantages but they all have tradeoffs. I went with the energy poly which came with my pol control arms https://www.performanceonline.com/19...ntrol-arm-set/ which are assembled and waiting for free time to install. I almost went with rubber since my car is a street cruiser. I had a set of energry poly bushings I already bought before buying the pol arms and they were the same as what came with the arms. they come with the grease and are slotted to hold the grease longer so we shall see how they work out.

 

I guess I do not mind being a myth-buster when it is warranted, and this is one.

This is a too-generalized myth. This is partly true and partly false.

I understand the chemistry and the physics. Many just pass along internet "info".

To quote Paul Harvey, here is "The rest of the Story":

Delrin is ideal for low friction rotating suspension bushings like control arms. It is very low friction. It wears much better than poly. There is rotation only, there is no axial articulation, The compressive forces are not too severe. It is very long lasting there. It eliminates almost 1 degree of negative camber change under load vs rubber bushings. Same with toe-in changes. You can most definately live with them on the street. I did for 30 years. But if you do not corner frequently at .9G or more, why bother. That is where the big impact is. There is only a minor steering impact at normal Gs.

Delrin is not typically available for sway bar frame mount bushings, and poly is a reasonable substitute there. Poly does not wear as well, and must be greased, but at least that location can be easily accessed for maintenance and replacement if required.

For almost any other suspension location neither Delrin nor Poly will last long. All the other locations do more than rotate, they have "compound movements" including severe compression and articulation. This extra articulation destroys the bushings. Neither material will last long under repeated strong compression, that is not what they are good at. This is likely where the myth comes from. This list includes: trailing arm bushings, rear strut rod bushings, sway bar end links, spring eye bolts, shock rod eyes, diff nose mount, subframe connector mounts, and body mounts. The Van Steel diff crossmember locator mount is however a good use of Delrin since it does not move and it is thin. The thicker body mounts are too thick and you will get cold flow, and I believe those are only available in Poly, which has much greater cold flow than Delrin.

There is almost no driver perceptable increase in noise or vibration when used in control arms. And I can guarantee you that the steering feels much more solid and controllable at the limit on a track car. The steering wheel feels more like a razor versus a rubbery mess at 1G. You can feel what exactly what the tire is doing at the road surface so much better. The tire has plenty of rubber to stop most NVH concerns. And there is no "clanking" unlike metal bushings.

Now someone, anyone, give me just one logical reason why Delrin is not superior as a control arm bushing?

Myth Busted.

https://www.corvetteforum.com/forums...rvettes-2.html

 

Oh I totally could be wrong. again im going on videos blogs and forum statements from others.. If you google delrin vs poly you get all sorts of stuff but the general consensus is for street cars rubber or poly is prefered. I do understand the different application points do matter. Ive also read here on more than one occasion where people have claimed to replace thier poly bushing on thier c3s for rubber which they claimed to prefer the ride quality from. This is why I stated opinions vary. YMMV I guess. I would expect the delrin to transfer the most vibration and have the least amount of unwanted play (or wanted play/give depending on application) and maybe I should have considered it further for my car. One things for sure, anything will be better than the 50 year old rubber thats left in there now.

Ridetech claims that the delrin is superior in performance to rubber in all areas except one, ride quality, which does matter to me for my street build as with poly im looking at some tradeoff in ride quality for performance but not full on go cart handling.
https://ridetech.com/why-you-need-de...sion-bushings/

I did go with the vansteel rear axle mounting/lowering kit which I believe uses delrin pucks.

 

There is a very tiny amount of degradation in ride quality. It occurs when you hit a pothole, crack or tar strip. It is a slightly sharper feel. It is not all that noticeable, or bad, and you quickly become accustomed to it. Certainly not what I would call objectionable. It is a very minor tradeoff for the crispness that shows up in the steering wheel. You still have 3-4" of rubber in the tire sidewall. You did not remove that much rubber from a bushing, maybe 1/4"

Go to the autocross portion of this site, and listen to people who have tried all 3, and poly is universally despised. Delrin is the clear favorite for control arm bushings.

 

I was one of those who bought the bushings from VB&P, and coincidentally, we wound up selling the car before the bushings went bad............