UMI control arm roto joints vs poly

Discussion in 'The whoa and the sway.' started by TTNC, Jul 23, 2020.

  1. TTNC

    TTNC Well-Known Member

    I've been considering swapping out all my stock control arms for UMI pieces as well as their front and rear sway bars, control arm and chassis braces, etc. I already have Viking coil overs at all four corners. I've read that UMI recommends for a street car to go with the rear control arms that have a polyurethane bushing at the chassis end and their proprietary delrin "roto joint" at the axle housing end. I think I also read on here a recommendation that you use spherical bushings (which I guess is what UMI dubs their "roto joint") at both ends of the arm.

    UMIs explanation is that the control arms with both bushing types will be a good compromise between road noise/harshess and good handling, whereas having the roto joints at both ends will be noisier/harsher.

    I'm looking to understand just how dramatic of a difference it is between the two options. I did ask UMI this question and they just restated the above about it being a good compromise. Also they stated opinions vary. Looking for opinions here.
     
  2. Skyhawk

    Skyhawk Well-Known Member

    I personally think the umi stuff is not as good as the HR parts.
    Plus buy from a vendor that supports the buick clubs and events.

    The quality is much better also.
     
  3. Ken Adams

    Ken Adams Well-Known Member

    I have UMI suspension parts installed on my GN and am satisfied with their quality plus the improvement in handling. One other thing, UMI parts are made in the USA.
     
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  4. TrunkMonkey

    TrunkMonkey Well-Known Member

    The rod end (Heim style) is the harshest/stiffest and would not be best for daily/street driving due to wear issues of the joint. But provides the best performance of tighter tolerances and motion.

    The delrin/ball (roto joint) is similar in action, but the delrin can be replaced, and the joint itself can be adjusted in it's tolerances.

    The polyurethane bushings offer the "smoothest" ride due to the "give", although they can bind if over-tightened.

    I run UMI on both my '64 (everything) and my '68 (everything except front upper and lower arms, those are still stock).

    I have the roto/poly upper rear arms (to get proper drive angle).

    I have been satisfied with the UMI products, but it is daily street driving, and Florida, so no "Canyon Carving" style driving. Just avoiding blue haired ladies...

    Someone driving fast and furious, might have better input.
     
  5. 1969BSGS

    1969BSGS Active Member

    Nick, I went with the #401417-B Rear Control Arm Kit, My Skylark is a Turbo 350 trans & Looks like you have a 200-4r , I think this is fine for a automatic car, No noises & ability to adjust upper & lower arms for pinion angle... Think you would be happy with this...
     
  6. TTNC

    TTNC Well-Known Member

    Not looking to do any serious corner carving, I just want to fix the lean and not feel like I'm going to slide off the seat sideways when I drive around rotaries and potholes at even low speeds. You go over certain bumps with it and you can feel the rear end wobble side to side. Just looking to tighten the handling and maybe stiffen the frame a bit.

    I'm also hoping that by stiffening up the frame with the control arm braces and shock tower brace that less twisting motion will get transferred to the body shell and that will help stave the common issue with convertibles where the paint cracks on either side of the panel between the top and decklid.
     
  7. Houndogforever

    Houndogforever Silver Level contributor



    I like the way Global West explains how everything moves in these videos.
     
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  8. 72gs4spd

    72gs4spd Well-Known Member

    I currently have stock suspension in the front with poly bushings and Hotchkis in the rear with frame brace . I installed the UMI front and rear Swaybar kit. What a difference it made.
     
  9. Lucy Fair

    Lucy Fair Nailheadlova

    Polyirethane is not suitable for any control arms at all, especially in the rear. I made me a custom set of rear lower and upper arms from 7075 aluminum. I used Spohn roto joonts on the frame side and QA1 hm12 uniballs and there is no noise whatsoever. I live in Poland and our roads are far from smooth. Pamhard has the same configuration except it's made from DOM cromoly tube. Billstein b6 are controlling motion. Now it handles like a dream. I can outrun a lot of European Gt's. I tried the Poly road amd it's a waste of money. I think poly can have its place but rather on drag than road car.
    Hope this will help some.

    Peace,
    Kacper.
     
  10. Oldskewl59

    Oldskewl59 Gold Level Contributor

    I am considering the UMI roto joints. My goal is touring, eventually. All the rear bushings need replaced, one way or the other, and I thought I had settled on Moog rubber. My question is; how do the roto joints hold up over time and miles?
     
  11. Lucy Fair

    Lucy Fair Nailheadlova

    I have about thousand street miles on them and they are still like new, same as qa1 rod ends.

    Peace,
    Kacper.
     
  12. TTNC

    TTNC Well-Known Member

    So we have conflicting reports then. If you ask UMI they'll tell you the arms with poly bushings at one end and roto joints at the other are quieter than the arms with roto joints at both ends.
     
  13. 72gs4spd

    72gs4spd Well-Known Member

    Makes sense to me, but I’m no expert. Question is how much quieter and how much of a performance difference is there? Just thinking out load.
     
  14. 72gs4spd

    72gs4spd Well-Known Member

    Just ordered UMI front control arms with .5 lowers and .9 uppers. Wheels and tires on the way as well.
     
  15. TrunkMonkey

    TrunkMonkey Well-Known Member

    I cannot hear mine squeak at full throttle.... :D
     
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  16. TTNC

    TTNC Well-Known Member

    That question is exactly why I started this thread. I understand it's a hard thing to quantify, but I'm looking for more information than just saying one is better than the other.
     
  17. TrunkMonkey

    TrunkMonkey Well-Known Member

    Possible that as there are three type of applications, poly bushing, roto joint, and rod end (heim type), hope this can help clear up some of the questions.

    I talked with Ramey Womer a while back on all of these. (Ramey is a good guy and willing to help)

    His reply was that the Poly provides the smoothest ride, but may have more "noise", but are best for daily driver, and long term use.

    The Roto joint is the better for both "noise" issues and they can be rebuilt (the delrin layer/lower cost) over lifetime use.

    The "rod end" (cannot call them Heim joints due to trademark) are the best as far as being free from binding, tolerance/tightness and noise, and are better suited for drag/track, but not "daily/street" use due to wear.

    And at the end of it all, the roto joint is the best for street/daily driving, the "rod end" for drag/track or serious road course, and the poly for long term (but might have some noise) and that can be minimized with periodic lube.

    And lastly, since most applications use "nylok" nuts, torque to 65 ft lbs, so no excess binding due to clamping force from the control arm that might occur from higher torque values.

    Hope that helps.
     
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  18. TTNC

    TTNC Well-Known Member

    Thanks, but again with the conflicting reports.
     

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