BOSS 302S FLCA Bind

[DocB]

A question for those of you running the BOSS 302S FLCA (M-3075-RA) with the Competition Front Bushing Kit (M-5638-C):

With no other suspension components attached to the arm, and moving the arm up and down within its range of motion, how much "bind" do you have and what do you believe is acceptable?

 

[DocB]

We spent the better part of Saturday on these darn bushings. Had them on and off so many times that we wore out a set of bolts.
Whoever made these for FRPP must have been using a yardstick as a measuring device. This pertains to both the set on the car and a brand new set of arms and bushings in stock, used as a comparative control, on the car and on the bench. Both left and right sides exhibited the same unacceptable bind.
We wound up machining the actual inner delrin bushing and the thrust washer rings on the lathe. Got the force to move the arm up and down from 35 to 14 lbs. Required machining of the inner bushing allows it to move freely now. The consensus was that if we took any more off the thrust rings we might totally remove the preload on the bushing making it sloppy and introduce some toe change.
At this time, the arm does not droop under its own weight, but I am hoping that it will "wear in ", or it will require further modification after my two upcoming events for the season.
As these were installed 3 years ago before I new any better, it just irks me now that big name, high dollar parts are sold as bolt on, engineered, quality controlled, race parts.
Additionally, thinking of others, how is a fella supposed to do this if he doesn't have access to a machine shop and lathes? Rhetorical, but just sayin'.
Hope the above info on the required modifications helps someone in the future before these bushings are even installed.

 

[ArizonaBOSS]

Interesting saga. Didn't really have any data or experience on this question so I didn't comment.
With poly bushings the effort to manually lift the FLCA up or down (for example, when mating ball joint to spindle) isn't much, but there is some slight resistance. The arm will fall down under its own weight if released.

I am assuming you have properly greased your bushings etc before install; don't have any experience with the delrin bits.

 

[Norm Peterson]

Are the bushing sleeve centerlines truly aligned on the same longitudinal(ish) axis? If not and they're slightly skewed, you will get some resistance to rotating the arm about them because it'll be trying to rotate about two slightly different axes. The stiffer the "bushing" material, the more noticeable the effect.

You may be able to diagnose this with a length of round stock of OD as close as possible to the ID of the sleeves.

Norm

 

[DocB]

Norm, centerlines are aligned.
I can truely say that the bind is in the bushing itself because if I SLIGHTLY back off the front lower control arm bolt from spec torque the FLCA will drop under its own weight as the inner bushing sleeve rotates about the bolt.

 

[Norm Peterson]

Basically, some of your bolt torque is still compressing the bushings instead of making joint clamp load. Either the front bushings are still a tiny bit longer than their inner sleeves (at least somewhere) or the chassis-side brackets are being deflected enough under full bolt torque to start axially compressing the bushing material somewhere. If it's the brackets that are getting 'squeezed' into the bushings, it won't be uniformly so. It's even possible that some roughness, sheetmetal bend radius, or other minor unevenness on the insides of the chassis brackets is involved.

Norm

 

[TMSBOSS]

When I have changed bushing on other cars, interference in the bushings was designed in. You assembled the control arms and put the car on the ground then tightened the final bolts on the bushings. Since there is no bearing surface, nothing actually rotating, this affectively centered the bushing. Is this the case with our bushings?

 

[DocB]

No, this is not the case with our race bushings. They rotate about the mating bushing surfaces from lock to lock (max up-down movement) of the FLCA.
Norm, like I said above, I was thinking about reducing the thickness of the fore and aft thrust rings that lay against the chassis (k-member) tabs, but am afraid that it will allow some toe change under heavy cornering.

***We are thinking about adding/welding in some stiffening plates to at least on of the tabs.

 

[steveespo]

Has anyone asked Ford Racing if these are supposed to travel freely or if they are supposed to have resistance from the bolt clamping force. My used set moved fairly free after 3 seasons of use, I just installed a fresh set with a new Ford bolt and the factory torque value and they are tight. Probably 35-40lbs of force to move them. Both bushings are greased with White Silicone Super Lube. There is so much force involved with the car weight and dynamo load that I don’t think this is truly a bind. Would love if a Ford chassis engineer could chime in @Shonuff82


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[Norm Peterson]

Bushings that accommodate all of the required rotation as 'sliding' between the bushing and the inner sleeve are supposed to be able to rotate freely. For that to happen, the sleeve needs to be ever so slightly longer than the bushing. Like maybe 0.01" - 0.02". The amount of toe change from the FLCA moving that small of an amount in the fore-aft direction should be negligible.

If they "freed up" after some amount of use, the bushing material either wore down axially or perhaps cold-flowed over time. Polyurethane is notorious for the latter.

Having difficulties today, losing power because of having a new service panel installed took everything down (like the router).

Norm

 

[Norm Peterson]

Bushing drag is essentially friction damping, which has one value for the static condition and one other value for when the suspension is moving. This typically adds harshness and provides maximum damping when you don't need any damping at all.

Bushings so modified rarely - if ever - squeak.

Norm

 

[Albino500]

Is the FLCA front mounting hole round or slightly ovaled on your K member?

 

[DocB]

I am 99.9% sure it is round and not ovaled. Everything was looked over very carefully.

 

[captdistraction]

did anyone note a gap in the rearward thrust bushing to the arm? I'm concerned this could present an issue under braking:

 

[DocB]

Yes, there is a gap there.

 

[ArizonaBOSS]

Yes, there is a gap there.

I think everyone will agree that a gap is present; the question is is it supposed to be there or not?

 

[Tri-bar]

No gap on mine, When I first put them on. I remember a small gap. Now there is no gap and looks nice a tight. I do run the polly 302R front bushing though in the arms right now. I did a side to side comparison with the 302S bushing. Offset seem to be the same.

 

[DocB]

There should be a gap.
If there was, and is not now, something is moving (and not in a good way).

 

[Tri-bar]

There should be a gap.
If there was, and is not now, something is moving (and not in a good way).

Nope all is fine, just checked to see what it looked like, small gap.