Delrin Control Arm bushing - what should be rotating?

[chr2002ca]

Fellow forum members,

Just received some new Hotchkis lower control arms(1109) for my '69 Camaro. Installed them to the frame this afternoon with factory torque specs of 85ft/lbs. As I move either of the arms up or down, the entire Delrin bushing turns with the arm. Occasionally you'll see the arm barely turn on the bushing, but mostly the entire bushing turns. This means the outside surface of the bearing(made of Delrin plastic) is turning against the frame. That just didn't seem right to me so I called Hotchkis and they said it was normal. He said that I should put grease on the outside of the bearing between the bearing and the frame. I told him the instructions make no mention of that and that the bearing itself will not be able to keep that face lubricated because there are no channels to do that. Besides, shouldn't the bearing be rotating inside the smooth surface of the arm and not against the frame? He also said the bearing should rotate easily by hand inside the arm, but my mine sure as hell don't. I pulled one arm back off and I can barely get the bearing to turn inside the arm while it's clamped in my vice. He also said the bearing would 'eventually wear in", but the only thing that seems like it's going to wear to me is that Delrin plastic surface that's constantly rotating against the frame, and that will get so worn(and then loose) that the bearing will always just turn there instead of the arm turning on the bearing as it seems like it should. I can already see some marks in the Delrin where it was rotating against the frame.

Is this normal? Anybody think the bearing/arm clearance might be off such that it's not allowing the bearing to turn inside the arm as easily as it should? Grease too sticky? What would you do?

Thought I'd check with the guru's here before I proceed any further. :thumbsup:

[GregWeld]

Think of it this way --- the Delrin bushing is going to "turn" against something --- either the inner or the outer or both... but as long as it's not SLOPPY -- it's doing it's job.

[65_LS1_T56]

Yeah, Greg is right, and on the next level, think about it this way: the control arm will rotatate at a given RPM (obviously never a complete revolution or you have other problems...) or some degrees per minute rate. It is better for wear that a smaller diameter rotates rather than a larger one. Smaller diameters have a smaller circumference, therefore have a lower surface speed. In essence, the speed at which the delrin bushing sees the inner sleeve speed is lower than if the bushing rotated in the control arm bore.
Lets just say the arm rotates at 1000 rpm, the inner sleeve to bushing sees that as 262ft/min (at a 1" sleeve OD). If it is the OD of the bushing rotates at 1000 rpm, it sees that as 471ft/min (at a 1.8" bore in the arm). The lower the surface speed, the longer the bushing will last.
Clear as mud? haha, hopefully that makes sense. Of course, it is just my opinion, not gospel.

edit: Isn't there an inner "sleeve" that takes the bolt crush load? From most I've seen, there is an inner sleeve about 1" OD that is on the inside of the Delrin. The bolt that holds the arm in the chassis tightens against this sleeve putting a compressive load on it and not on the bushing. It is
my opinion that the bushing should rotate on the sleeve, not in the bore of the arm.

[chr2002ca]

Yes, the Delrin bushing has an inner metal sleeve that takes the compression of the tightened bolt that runs through it. The Delrin bushing has grooves in it to allow grease to lubricate the inner surface that mates up against this inner metal sleeve, and it has grooves on the outside of it where it mates against the inside of the control arm. Whether the bushing rotates on the inner sleeve surface or on the control arm surface is NOT my concern since those have grease grooves to lubricate them. Where the Delrin bushing does NOT have grease grooves is the outside surfaces visible to the naked eye that mate up against the frame. Those are surfaces that I wonder about because those are the surfaces that are rotating against the frame surface. Yes, I can put some grease on those surfaces now before installing(not mentioned in the Hotchkis instructions), but once they are in, there are no grooves on that surface to keep it lubricated in the future. Additionally the frame surface is not perfectly smooth like the other surfaces, so the Delrin plastic rotating on would seem to wear. It's just strange to me that I'm seeing this plastic rotating against this rougher frame metal and knowing that when I pump grease into the grease fitting the grease is not going to reach that surface. I guess time will tell. I know lots of people are running Delrin bushings so I guess I'm just being paranoid. If, 5K miles from now, I see those bearing surfaces worn out with slop resulting, I'll print out this thread and send it to the makers of those bushings that Hotchkis is using. :yes:

Can't wait to put these new arms to good use along with my other Hotchkis gear.

Thanks for your input gentlemen. :thumbsup:

[Vegas69]

If you wear out those bushings, I'll be the first to shake your hand. :D I like Hotchkis and I think they will stand behind their product. At least that's my feeling meeting John a couple weekends ago. Grease migrates so I think it will end up lubing the bushing to some degree.

[CarlC]

Grease will migrate out as Todd mentions, and it takes very little lubricant to do the job.

The Hotchkis parts have been in mine for quite a while now with more track miles than I can remember. The only thing I've done is periodically re-lubricate the bushings. No problems.

[chr2002ca]

Todd, Carl,

Thanks for chiming in and for the reassurance. I guess it's just another case of me being a bit paranoid. The rest of my Hotchkis gear has worked great so that's why I continue to go to them when I can. I'm sure these arms and bushings will work great also.

Thanks again! :thumbsup: