Problems with SuperPro bushes

[manga_blue]

I'm struggling with these things and I'm wondering whether others have had the same issues. It's all about them getting too tight to turn freely during alignment and operation.

I've had a full set of offset Superpros in the car for 2 or 3 years. When we tried to corner weigh the car a few months ago we found it impossible because the bushes were bound up so tight that raising and lowering spring perches was having almost no effect on the weights at the wheels. i.e. the control arms were pretty much locked onto the bushes.

This week I've pulled all the steel inners out from the poly (which took a reasonably major effect with a puller) and regreased them with the special poly grease (the nasty sticky white stuff). When I pushed them back in I found I could only hand push them about 3/4 of the way, then I used multigrips to test that they turned and to push them home. They were pretty bloody stiff at that stage, even with fresh grease.

After they've sat there for a day we've found that we can't adjust alignment properly because some of the bushes are bound up again. We can't turn the inner steel bushes to get the offsets in the right axis. Even putting a bolt in and using the hex head to do it requires some effort.

The car is in a race shop that does historics and open wheelers. They say bushes should turn freely enough to turn with finger pressure if you can grip a little of the end. They also say they have had the same issues with nolathane on the other race cars. If they can't get them to turn freely enough so they can finish the alignment then they want to take them out to turn down the inner steel sleeves. Alternatively even if they do manage to set alignment they say the suspension can't work effectively while the bushes are so tight.

Has anyone else been there, done that?

[greenMachine]

I am confused. I have been running Superpro adjustable bushes in the GM for years. My only problem was the opposite of yours.

First up, the movement of the bushes (rotation to move the inner suspension pivot point) has absolutely nothing to do with the movement of the suspension (ie the movement of the suspension arms as the car travels over bumps, or rolls while cornering). The suspension bolts should not bind or seize in the bush, that suggests a bent bolt, or one that is the wrong size.

The bushes in my cars have been modified to prevent them rotating, as I have experienced them rotating so that instead of the offset suspension bolt providing neg camber, it rotates inwards under load (on the racetrack) to give me positive camber (and an embarrassing amount of toe out!). I have put a few dabs of weld on the face of the bush so that when the suspension bolts are tightened up this beds into the inner face of the housing and has proved 100% successful in preventing unwanted rotation.

I have just done a wheel alignment on the racecar, and we had to drop the inner end of the suspension arm, knock the bush out enough to grip it with multigrips and rotate the bush that way. It did require some effort. If yours can be spun with your fingers, I would expect you will experience the unwanted rotation under load that I experienced. A mod along the lines of my weld blobs would be an absolute must in this case.

I would not be machining anything just yet. I would first get to the bottom of why the suspension is binding/seizing, and fix the real problem, rather than do something that may have no impact on your real problem. My guess is that the difficulty in rotating the bush to get the alignment right has nothing to do with the binding of the suspension. As well as bent/wrong bolts, I would check the correct washers too. I am assuming the car has had no accident damage, hit kerbs etc, anything that might affect the alignment of the suspension mounting points?

Frankly, the line the people you are using doesn't sound convincing to me, and I wonder about their competence with an MX. Is there any way you can get the car to a shop that knows its way around an MX, preferably one that handles competition cars? Even if you could bring them a suspension arm and the relevant bolts they may be able to diagnose the problem ...

[manga_blue]

Thanks for the response, GM, sorry, not making myself clear enough here. When they were new then I had that problem (more of a minor nuisance really) with the whole steel inner turning too easily when you relased the cam bolt's adjusting nut to adjust with the cam. Now I've got the exact opposite.

The way these are meant to work is that the poly crush tubes are locked to the control arm housing by friction and compression while the steel inner is locked to the chassis mounts by the pressure of the bolts pinching the brackets onto the ends of the steel. All the rotation of the control arm then occurs between the knurled inner surface of the poly bush and outer surface of the steel inner.


We just don't seem to be able to get that "unrestricted pivoting" anymore. It's binding up instead - making it almost impossible to move for alignment work and restricting free pivoting of the control arms.

PS: using original undamaged bolts and undamaged washers. No issues between bolts and steel inners, just between steel inners and crush tubes. 1 lower control arm inner bush locked solid, 4 others extremely tight, 3 OK.

PPS: nice idea about the weld blob too. If I get these things moving normally again I might do that.

[manga_blue]

Edit: The way these are meant to work is that the poly bushes are locked to the control arm housing by friction and compression while the steel inner is locked to the chassis mounts by the pressure of the bolts pinching the brackets onto the ends of the steel.

[greenMachine]

I need to get to bed, before I say too many things that I regret ...

Yes, you are right, if the steel bushes are locked to the suspension mounting points, the poly bushes must rotate around the steel bush (or in the suspension arm housing). And yours are not. Actually, now that I think more about your problem I had this problem with my front ARB, and solved it by taking it apart, cleaning the bar and the inside of the poly mounts, and putting it all back together with fresh grease. Worked just fine ...

Best suggestion I can make at this hour is to take all your suspension apart, clean all the moving surfaces, and then re-grease (with that ugh stuff). Check that none of the steel bushes have become corroded, or gunked up with old grease (which was my problem).

If they worked 'then', there must be a reason why they won't work 'now'... and I can't see that machining the bushes is addressing the root cause of your problem, even if it does remove the symptoms.

Can you ring the people who you got them off, they may have a pointer as to what might have gone wrong. Or give Mania or Carco a call.

Let us know how you go.

[NitroDann]

The poly part is supposed to be locked to the arm, the inner metal tube is supposed to the locked to the bolt, so a bent bolt might help haha.

OP already said he has relubed everything.
The only way out of this that I can see is to subtly resize the metal inner tubes. You already have told us the issue is excess friction there due to a tolerance issue. So, change the tolerance. I cant tell you why this happens, but it is in no way abnormal, a lot of factory bushes have everything locked and the rotation is only achieved through sheer forces torquing the rubber.

Looks like youve answered your own question.

Dann

[tbro]

Hey Phil,

Have a look at the INSIDE of the crush tube.
Easiest way to do this is use a drill bit and it should slide through easily.
Even though the tube is fairly thick unit it will crush inwards onto the cam bolt on torque up.
Try the cambolt and make sure it is a nice loose fit and not binding at all.
As for the welds, weld two blobs onto the inner bush area on the control arm, that will stop the bush moving during suspension roll,
mine are usually about 1 inch long.(big blobs)
The problems your having are a common problem I've encountered on Porkers.
And don't you just love that grease!!!!!
Terry

Hope this makes sence as i'm off my face on painkillers atm

[greenMachine]

Good point Terry, but the bolt/tube(pin) are meant to be immobile in respect to each other. That will help installation, if there is a deformation that can be corrected, but it won't help the movement of the poly bushing around the crush tube/pin.

Can only be swelling of the poly bushing (unlikely?), or corrosion/gunk on the pin. I know you re-greased it Manga, and if the pin was nice and shiny/totally clean when you did that, then I would just replace this bush/pin. One way or another, that should fix it.

[NitroDann]

I think a lot of people have a misconception about how bushes work. Someone should do a writeup.

Dann

[manga_blue]

So my engineer spoke to Fulcrum's engineer ... turns out that they corrected a dimensioning error in the lower control arm bushes about 5 years ago which caused excessive binding.

Interference fit was reduced by 0.2mm so that they rotated more freely. This was roughly the same as my engineer had suggested removing from the steel inners.

Faith in my workshop and in Fulcrum is restored. They've both been good ... so far.

[manga_blue]

and thanks GM, Terry and Dann. Whatever it is I hope the painkillers work.

[greenMachine]

Good result Manga, and interesting information! I wonder if they told buyers about it?

Hmmm, I must check when I put mine in the GM, it was probably around that time ... Did he indicate whether this was just the adjustable bushes, or both the LCA front and rear bushes?

All the best Terry, and get well soon!

[manga_blue]

I checked and found that mine had actually been in for a bit over 4 years. All cleaned up, greased and with the springs off there's almost as much resistance as you'd get from a stock shock absorber. Apart from making it impossible to corner weigh my workshop says it plays hell with shock and spring rates.

Their engineer said that machining the inners was commonly done to overcome binding. Just figuring out now whether to install replacement poly or just machine the inners.