[icckart]

I've installed an UMI 1055 (dual roto-joint) OHB, and have an issue:

Initially, I had A LOT of noise, clearly coming from the PHB. A quick forum search showed that MANY people were running into similar problems. I general, the response was "roto-joints are noisy". Maybe, but I think I've found UMI's problem, and just spoke with their designer (Ramey Womer) about it. The issue is that they (UMI) have spec'd their rod-ends (roto and non-delrin "hard" spherical) to make SURE there won't be a clearance issue for the LOWER range - meaning the PHB will ALWAYS fit with the stock bolt. UMI spec's (confirmed with a real-time CAD drawing check while I was on the phone with them) for inner joint diameter is: Nominal = 0.560" MINUS 0.000" PLUS 0.010" - basically, they're erring on the "too big" side of the range, to make sure it will never NOT fit. So, per UMI's specs. their joint ID can be as large as 0.570"

The problem is Ford's STOCK bolt is nominally 0.540" (at least mine measures at that). I measured my STOCK PHB (both joints, both sides - all within 0.002") at 0.550" - but the new UMI 1055 is: 0.564" (per UMI, that's within their spec'd range). With the STOCK PHB, the STOCK bolt has a little "slop". With the 1055 there is A LOT of play - to be expected, since it's nearly 0.015" larger ID. That may not SEEM like a lot, but it IS. The PHB is in constant motion - so it's going to "slap" around (and make noise) on the stock bolt.

UMI said they don't offer bolt kits (like they do for LCAs and other products) for their PHBs, because the nut end varies so much (i.e. they use the SAME roto-joints for both Ford and GM PHBs). I told them they should SUPPLY the proper bolt with their PHBs, and let the stock "funky" flag-nut (in the Mustang case) be re-used. That way they could keep the tolerances much tighter.

This would certainly explain why some forum posters notice a lot of noise, and others don't. Right now, I'm relying on the 129 lb-ft torque spec. to "clamp" the rod-end faces tight enough to keep them from moving. It works for now - but it's not going to last long. There's way TOO MUCH force on the PHB for that clamp force to keep it from moving.

Note that it only takes A LITTLE play to make A LOT of noise. I initially found this when the jam nut on one side wasn't REALLY well tightened well (now with blue Loctite too).

UMI seemed responsive to the feedback, but don't really have a solution for me. I'm thinking about buying a pair of good quality bolts (stock ones look really crappy anyway), to use with the stock flag nuts. Actually, it IS possible to get a wrench on the back sides of the PHB mounts, so I probably could buy a bolt-nut combo (personally, I'd prefer that option). It'd be a little more hassle to install (but I've already wasted >2 hours finding the problem for UMI).


Anybody else run into this? If so, what did you do about it?

 

[Guest]

I have Spohn Del-Sphere lower control arms that were initially very noisy but their preload is adjustable. They come with a neat tool that can be used to disassemble for maintenance and also to adjust the preload to eliminate the noises. I did this adjustment twice and it has been months since I heard a single sound from them. I bet the Roto-Joints have something similar.

 

[icckart]

Yeah, the Spohn ones look exactly like UMI's roto-joint. Wanna bet they get them from the same manufacturer?

Anyway, that's NOT the problem. I do have the tightener tool - and did re-tighten the roto-joints. All that does though is compress the Delrin inner bushing more. Indeed (and others have posted this), that COULD be a source of noise - particularly if the bearing cap completely unscrews (although they now have a set screw to prevent this).

I actually tightened mine to the next "stop" (set screw position) - just in case. It's probably even a bit TOO tight now?!?

None of that will "fix" the inherent problem: The rod-end ID is TOO LARGE for the stock bolts!

 

[CCS86]

Yeah, the Spohn ones look exactly like UMI's roto-joint. Wanna bet they get them from the same manufacturer?

Anyway, that's NOT the problem. I do have the tightener tool - and did re-tighten the roto-joints. All that does though is compress the Delrin inner bushing more. Indeed (and others have posted this), that COULD be a source of noise - particularly if the bearing cap completely unscrews (although they now have a set screw to prevent this).

I actually tightened mine to the next "stop" (set screw position) - just in case. It's probably even a bit TOO tight now?!?

None of that will "fix" the inherent problem: The rod-end ID is TOO LARGE for the stock bolts!

I've been through this whole thing myself with Spohn. These kits aren't well engineered, they're just thrown together. Spohn's own adjustment tool (and the replacement they sent) doesn't even engage the adjuster ring correctly. I had to make a custom tool.

Lucky for them, the clamping force generated by the bolt is, in fact, enough to hold the ill fitted hardware in place. At 120 lb-ft torque on a 1/2" fastener, the clamping force generated is nearly 15,000 lbs. Even if the coefficient of friction between the spacers, bolt, frame, etc. was say 0.6 (it's likely higher with the local deformation), that is still enough clamping force to pull over 2 lateral G's in the car before it slipped.

I'd double check the torque on the mounting bolts, and the joint adjusters themselves. Even when mine were tight enough to need a long screwdriver to rotate by hand, they clunked. Spohn has no adjustment spec whatsoever. They tell me "as tight as you can get with a ratchet". You've got to be effing kidding me. What a bunch of clowns.

I have a feeling the joints need a high preload, followed by some spirited driving, then a retorque, to settle down. I think the delrin cups deform to fit their housing, but only after they've had some abuse.

 

[Guest]

I have a feeling the joints need a high preload, followed by some spirited driving, then a retorque, to settle down. I think the delrin cups deform to fit their housing, but only after they've had some abuse.

Pretty much what I experienced. Torqued, drove around for a week, re-torqued. It has been quiet since at least early summer.