Spring bushes.......

The correct term is polyurethane, this material is much tougher than rubber and can be greased to extend the life of the bush. As rubber cannot be greased, it is normal practise to install Polyurethane bushes when fitting greasable shackles.

Polyurethane bushes act by rotating on the central steel tube in an application like a spring shackle. This rotation will quickly cause wear between the tube and the bush. the greasable bolts usually have holes in the sleeve to let grease between the centre tube and bush. Also as part of the deal unless they are greased they can squeak annoyingly.
I had poly bushes in my Range rover panhard rod. One trip to the Simpson and there was about 1MM play between the inner sleeve and bush.
I changed back to rubber as in that application all the movement of the type of bonded bush is within the rubber in shear, so there is no rubbing wear, but they might be OK in leaf spring shackles where even the rubber has a rubbing rotation wear.
regards Philip A.

Polyurethane bushes can be quite squeaky which is a PITA. Greasable shackles stop the squeak and they also allow the leaf springs to move easily, so are supposed to improve the ride.

Rubber bushes have changed a bit. Many of the ones on later leaf spring vehicles (eg 78/79series) have a steel sleeve, so move pretty freely.

I'm running poly bushes and greasable shackles on my vehicle, but given my time over again, I'd stick with factory bushes.

Thanks for your replies, I had a broken spring hanger in the front and was wondering what to replace it with. I might go with the factory rubber bushes after reading your replies.
Thanks again
cheers
Reiner

I have just replaced the front springs on my hilux all OME and have put in greaseable shacklespins etc and have used rubber bushes as the other ones wear the pins away and eventually when you need to replace the rubber bushes you will have to do the pins as well.The other ones squeak and also do not have the flexibility that the rubber ones do, and yes the rubber can be greased without the grease damaging the rubbers. Regards Steve M

Reiner
Have never been totally convinced re non-rubber shackle bushes for anything except extreme off-road use. Not even 100% convinced then.

A colleague has a 4WD converted Coaster with greatly increased spring travel and axle articulation and the original rubber shackle bushes have survived any number of cross-Australia trips.

Rubber bushes confer useful torsional and other flexibilty, and this reduces suspension component stresses.

As typical life of a rubber bush is at least 100,000 km - what advantage is the claimed added longevity? Greased bushes need regular greasing - this adds to maintenance costs.

I'll buy arguments about more precise axle location - but this can be contradictory to the torsional and other stresses then passed on to other bits.

I vaguely recollect (from my research engineer days) telling a designer that 'an ounce of rubber can be worth a ton of theory'.
Collyn Rivers

Reiner
Should add to my response re rubber bushes - that my comments do not apply to racing cars nor serious sports cars, where rubber can introduce unpredictable steering effects.
Collyn