Lubrication of Polyurethane Wishbone Bushes

[Laurence7]

I have a feeling that this one's been asked in the past, but I'll ask again anyway.

In the past, I've used red brake rubber grease to lubricate the polyurethane suspension bushes (seemed like a good idea at the time), but I suspect this stuff may not have either the pressure-load capability or the lubricity (nice word!).

On other forums I've seen people recommending copper-slip grease, but I'm not sure that's a good idea if its mineral-based (Polyurethane doesn't like mineral oil apparently).

Other sources suggest that either silicone grease or synthetic-based lithium grease is the thing, but some of these are very 'thin', so may easily migrate out of, or get washed out of, the bearing.

Yet another source suggests that a high-tack grease is what is needed, to ensure that the grease stays where it's needed.

Can anyone offer any informed advise please?

Laurence

[splitpin]

That takes me back ............ they're self-lubricating aren't they .............. just like the ones in the swinging arm pivot of my then new Suzy GT750 that had them .............. yep, the ones that were shot in about two minutes flat, which got replaced (by me and most everyone else at the time) with proper phosphor-bronze ones.

Luckily, they don't get worked so hard in a nicely widely triangulated wishbone pivot.

Rather than following variable 'I use, whereas he/she uses' folklore, I'd be inclined to have a word with a technical boffin at someone who actually makes them, for example, Powerflex 01895 460033

[BertBert]

I dont think the bushes need lubricating. I'd put copper slip on the bolt where it goes through the metal sleeve, but not anything on the bushes themselves.

Bert

[Laurence7]

BertBert said:

I dont think the bushes need lubricating.

Ooh, not sure about that Bert. I'd agree if we were talking about a rubber bush, but a polyurethane bush works very differently.

A rubber bush is effectively bonded to the inner sleeve and the outer housing and works by torsion of the rubber as the suspension arm articulates.

With polyurethane, the bush is essentially 'rigid' and, as the suspension arm articulates, the bush runs on the crush tube, which is rigidly clamped to the chassis structure. Since polyurethane isn't self-lubricating, some kind of lubricant is needed between the polyurethane bush and the crush tube to reduce stiction and excessive wear.

When you buy polyurethane bush suspension kits for road cars, the kit comes with a little sachet of unidentified magic grease.

The question is - what is the magic grease?

[LCM]

Swap them for PTFE bushes?

[BertBert]

What was I thinking?

This is what you need...
http://cgi.ebay.co.uk/SYNCO-SUPERLUBE-MULTI-PURPOS...

ETA I wouldn't worry about it staying in. It's not in a long-life environment and could easily be refreshed.


Bert

Edited by BertBert on Sunday 29th May 11:31

[splitpin]

Although that seems about right (fully synthetic / silicone / waterproof), for the sake of a phone call if I was going looking to go more high tech than 'Fairy Liquid Plus CG and/or WD', I'd still check it out with someone like Powerflex.

Pretty sure the stuff that the pros use is specially developed for this particular usage; incredibly 'sticky', kind of halfway between a heavy grease and a non-setting sealant.

I think that would be the quickest and most sure-footed way - I had a quick stroke through Dow Corning's Lube Products Spec List the other night and as one might expect, the range of what to use for what is totally mindblowing.

[BertBert]

I agree, but it's not a high tech environment! There's plenty of references on the net to lubricating poly(urethane) bushes.
Bert

[Laurence7]

BertBert said:

This is what you need...
http://cgi.ebay.co.uk/SYNCO-SUPERLUBE-MULTI-PURPOS...

...so I looked up Synco website and found this compatibility chart...

http://www.super-lube.com/files/pdfs/Super_Lube_Co...

I'm happy with that!

Thanks guys

[BertBert]

Excellent!