I have fitted poly bushes to my suspension (all top hat style with metal sleeve through middle). I have been led to believe that the PU is self lubricating. I am a little confused as to whether to apply grease to where the bush contacts the mounting bracket. Plus logic tells me that the bolt through the metal sleeve should be greased (metal to metal contact and all that). Just thought I would check before I grease everything then have to degrease it later !!!

If they are the same as mine (MK) the metal insert is slightly wider than the poly bushes and is clamped when the bolts are tightened. Its the bushes that move not the insert so no metal to metal grinding. Good spray with WD40 or double-T should cover it. Ring your supplier for info (as long as it's not the men in tights cos their tech support is crap)

For the sake of dismanteling in the future, put a thin smear of coppaslip on the bolt so it doesn't sieze in the tube.

This topic has been well covered before, but here goes again.
Bolts should never be used as pivots, it's just plain bad practice. The crush tube through the centre of the PU bushes is the pivot, and as such needs lubrication. The correct grease for PU in this scenario is moly disulphide. It is the colour of pencil lead, and should be available anywhere.
Apply it ONLY to the OD of the crush tube, the ID of the PU bushes, and the outer faces of the top hats of the PU bushes.
It WILL go off,so from time to time, you'll need to dismantle the bushes and re-grease them.
As Viper states, use an anti-seize lubricant on the ID of the crush tube to prevent it from corroding to the bolt. Use it very sparingly, but if the crush tubes are stainless (as they should be) don't bother with the anti-seize.
Torque up the bolt so it clamps the crush tube within the chassis bracket, you don't want the crush tube to revolve on the bolt.
If you have the black rubber (Metalastic) bushes as used in Triumph Heralds, the crush tube will still need to be clamped tight. The rubber merely deforms and contorts, which provides just about enough compliance for the suspension to work.

Thanks chaps, I take your point Rorty about some subjects being well covered however you have to bear in mind that members are joining the forum all the time, so many will have missed threads previous. Maybe theare should be a reference archive for particulary useful or hard to come by information ? But then I guess who decides what goes in it, could get very subjective.

with regard to shock absorbers , how should thses be tightened up ? ie bolted up so that the small amount of movemnt is taken up by the rubber of the bush , with no movement aroun the bolt (as with the metalastic bushes ?)

thanks , Phil

Yes, absolutely...tighten them up (when all is fully laden at correct ride height)

The bonded rubber type ends are NOT bearings and the crush tube in them must be clamped at each end.

Some coilovers DO have bearings, spherical type, but all the movement is contained within the joint, so the same same applies....tighten it up.

As has been covered previously, pivoting bearings are OK....must be designed for the job. Check out my top wishbone design.


pivot design click here

Notice there is a hardened shaft that cannot rotate and the pivoting parts are fitted with bronze bushings so they can rotate.

Hi Alan,

I'm going the 'inboard' route as well. I hope you don't mind but I've used your design as the basis, just modifying it to my specific application. What are you using for your castor bushes. Are standard stainless steel washers okay or should they be of a specific material.

Thanks in advance,

Martin

Martin,

I'm using an aluminium or steel spacer machined to fit, or nylon/delrin would be OK.

Yes, I guess stainless would be fine too as you should have the bronze face on the flanged bushings to bear against.

If I was concerned about people copying or being inspired by my work I certainly wouldn't be publishing it on-line...:-)...I'm flattered to be honest...let me know how it works our for you.....

Thanks Alan,

I kinda guessed you wouldn't mind or else, as you say, you wouldn't be posting details on here!! Thought it was the 'honourable' thing to do to mention it though. I'll post some pictures in the photo section and let you know when I've made some progress.

Thanks again,

Martin

thanks Alan for the info on the shockers

Phil

FAO Rorty, or anyone else for that matter...

quote:

---

The correct grease for PU in this scenario is moly disulphide.

---

Polyurethane is resistant to attack from oils and greases (unlike a lot of rubbers) so you could use lithium or moly grease if that's what you have. Copaslip, although it comes in similar tubs to grease, shouldn't be thought of as a lubricant - it's an anti-seize compound.

Cheers,

Eddy