Trailing arm pin bushes

[bwaminispeed]

Want to convert my trailing arms to bushes both ends......Don't know who decided to put roller bearings on the one end, but, they are entirely unsuited for the purpose.....

Does the conversion use the same bush both ends, or, is a different size needed to replace the roller bearing???

And, if so, what size is required......

[rpb203]

I believe that the really early trailing arms had the bronze bushes at both ends but it was decided to change one to bearings, not sure when but sure one of the '59 people will know.

[woodypup59]

I THINK - the earlier trailing arms had a smaller bore at both ends.

I haven't got mine to hand to check.

[bwaminispeed]

Yes, I knew that, and, the change to a needle bearing was a bad idea.....Needle bearings are intended for continuous rotary motion, not the very small (almost none existent) radial motion they get from trailing arm movement....

Rather than change the bushing to a needle bearing, they should have fixed the grease channels so both bearings actually get greased when the grease gun is applied, as shown in the Tech posts......

[woodypup59]

Some people have drilled the inner end and fitted a grease nipple there.

[Spider]

The bushes used in the arms, IMO, aren't much good. They are steel backed with bearing material plated on to that. There was a TB for the early cars to drill and fit a grease nipple to the inner end, only, with the hardness of the shafts on the ends, well,,, good luck drilling that where it needs to be drilled.

Proper Bronze Bushes perform way better than these and yes, I agree that in all suspension arms, Bushes are what should be fitted, not needle roller bearings !

The Bearing has a bigger OD than the standard Bush. From memory it's 1-1/16" OD x 13/16" ID x 1.0" long. The only detail I'd like to add is that if going to Bushes, some consideration for a grease path I feel is needed. As a couple of ideas, a spiral in the Bush is possibly the easiest to do, but perhaps a spiral in the shaft with be better ? I feel it should spiral, rather than be straight to ensure when greasing, the grease goes all the way around the Bush instead of a single line, probably on the unloaded side.

[minibitz]

Despite the fact that a needle roller is not considered suitable the thing I have found interesting is that of the umpteen arms I have rebuilt for customers it's always been the bush end that's totally flogged out.

I get the odd one where the needle roller is rusted up due to lack of greasing and I would imagine this to be more of an issue in countries that salt roads during winter, which isn't an issue here in NZ.

[smithyrc30]

Funnily the top arm on the front suspension has two needle bearings.

I would imagine that they generally get the same lubrication schedule as the rears by any one owner, maybe less because they are harder to get at.

They have approximately the same rotation as the rears and yet carry more load consistently than the rears.

They rarely seem to fail.

A lot of effort seems to have been put into increasing the supply of grease to the inner rear arm needle roller when it is rarely the one that fails.

Clearly the inner bearing was an issue on the very early cars because BMC chose to modify it by adding a more costly solution to the assembly. Presumably to reduce warranty costs/failures.

I just disassembled a front and rear hydro frame, both BMC Australia originals (I was told they came from a 1970 car), the front has cracks in the steel around the front cross beam and around the lower suspension arm mounts. The rear is cracked around the inner and outer mounting plates for tharm and rotted where the hydro units sit.

Clearly the car had not had an easy life

The front suspension arm bearings are like new, still had grease on them and the surfaces still intact on the shafts. I have not cleaned the bearings out yet but I do not expect to see issues give the state of the shaft.

The rear inner bearing is fair, the surface of the shaft has visible markings where the bearings have sat, indicating that the grease was not present or had failed. The bush side is mullered. The shaft is worn badly, the bearing almost none existent. There is evidence of grease in the shaft between the grease nipple and the (now blocked) exit hole so it was lubricated at some point in its life. The grease nipple still seals, so water/grit did not enter through that.

Given that we have three other points on the suspension that do not fail as regularly as the outer bush, it would be a high confidence assumption that the location is a significant contributor to the failure rate. At the rear the outer arm bearing sits in all the wheel debris flow and the seal edge is in the same plane as the tyre rotation. The inner has the same vertical displacement from the ground but does not sit in the wheel path.

At the front the bearings are higher off the ground (water ingress through streams and tyre fling off is much lower) and the seal is perpendicular to the wheel axis.

If we rate the failures there would be a one in ten for the front, maybe a four or five for the inner and maybe an eight or nine for the outer.

In terms of load capability, bushes and needle roller bearings have way more capacity than the mini requires as long as they are maintained correctly.

So it's either the location of the bearing and sealing system or the maintenance that kills them or both.

I look at the original radius arm grease nipple cover and wonder if it was extended inboard to cover the seal as well if the rate of failure would go down

[Andrew1967]

Reading this thread and comments with interest.

I have to agree with Minibitz, in that the vast majority of radius arms I've seen and dealt with over the years, the bearing is nearly always perfect or serviceable. Obviously when rebuilding a car to the standards we all do them to now, then the bearing is replaced regardless when fitting a new bush and shaft.

It's the bronze bush that is always the one that's knackered, usually down to poor or non existent greasing.

As Smithyrc mentions, the top bearings arms at the front are rarely worn, so much so, I have never replaced upper front arm bearings and shafts in any of my project cars, as they haven't needed to be replaced. That said, HOY's upper arms were shot (rusty beyond belief and poor shafts), so easiest option was to use a pair of replacement arms with perfect bearings and shafts.

I'm not convinced of the advantages of retro fitting a bush to the inner side of the radius arm, much better would be to modify the shaft as per the Tech post put up by Peter Laidler, if I remember correctly. But even so, it's not the bearing that causes the problem in most cases.

Keep the arms regularly greased, that's the key.

[woodypup59]

This is fairly typical of top arm shafts that I encounter.

As cars get older and scruffier, maintenance tends to wane.

The left end is actually worn down with a step, the other looks similar but just has witness marks from the needle rollers.

I agree that a plain bearing should be better for these applications where there is very little rotation, but I can only think that the bushes and bearing are undersized for the loads encountered in practice. Mixed materials and salty water don't help.

The other thing is that, whilst not actually designed to a life of 5 years like modern cars, the cars have been around for an awful lot longer that Issy, JD et al could have imagined.

After all, who greases their nips every week ?

[Spider]

The issue with the factory bushes in the rear arms is not that they are bushes nor the lube, but that they are cruddy bushes. Not much more than a bit of tin plate rolled up and some brass plating. They also have a poor grease path.

Proper solid bronze bushes are better than these.

What do the use in the Knuckle Joints on Trucks ? Not bearings and not tin plated bushes either.

[CooperTune]

I machine oil-lite bronze bushings for the front uppers and rears for my race cars. I like to take small cuts holding a ice cube to the back of the work to avoid the lube escaping. Cutting grease passages is required but I feel saving the old metal tubes is most important. The plastic ones are not worth installing. I extent the bushings a little and machine a step that engages the tube forming a seal. No grease gets lost in the arms. Steve (CTR)