Rubber or polyurethane bushes

[GavinL]

Recent article in Safety Fast! the MGCC magazine, 17 year old poly bushes fitted to a 1950s MG TF.

[philthehill]

There does seem to be a change in the maintenance of poly bushes over the last few years. Originally it was not recommended to grease or lubricate poly bushes. That seems to have changed latterly as all the good quality bushes that I have bought recently are provided with a pack of lubricant.
In my experience poly bushes do need to be lubricated with - red grease the preferred lubricant but general purpose grease seems to be acceptable.
If the poly bushes fitted to the MG TF had been lubricated there is a good chance they would still be serviceable.

[jaekl]

Shouldn't they be shorter than the rubber bushings they replace? The rubber ones typically are longer than the metal pieces so that they are compressed in order to "clamp" into place. If the poly ones are too long such that excessive clamping pressure is generated, the necessary rotation may be at an undesirable location. Perhaps the ones used here weren't sized correctly.

[philthehill]

Poly bushes used on the Minor do not have a central tube to maintain the distance between the clamping plates.
The space between the clamping plates re Morris Minor is maintained by the shoulders of the pin i.e. Eye bolt pin - bearing surface 1/2" diameter with a 3/8" dia thread either end. The rear spring eye pins are the same 1/2" diameter bearing surface with a 3/8" dia thread either end.
If you change the eye bolt/rear spring eye bushes to the J4 Metalastic bush then the bush comes with a steel centre tube which has to be set to a given specific length to give adequate clamping of the central steel centre tube.
The original BMC rubber bush where it fits into the eye is 21mm long. Only a few of the Poly bushes I have are the same length as the BMC rubber bush
The majority of the 36 NOS Poly bushes I have are of 18mm length where it fits into the eye - so 3 mm shorter than the original BMC rubber bush.