Poly bushes

[les]

I’ve noticed there are two types of poly bushes available for the rear spring shackles, maybe more, different manufacturers seem to decide their own specifications, typical of most stuff now. The difference with the ones I’ve got is in the flange thickness, one set (blue) is thinner measuring 2 mm, the other set (red) measures 3.5 mm. Anyone else noticed this ? Both sets bought for the same job.
The original rubber bushes were all the same and of course compressed more easily. I wish I had bought rubber now, although I suppose the rubber would be of inferior quality. You can’t win !

[svenedin]

I hadn't noticed differences with the rear suspension bushes but then again, I have only just recently changed to poly bushes and had no prior experience of them. At the front there are definitely differences in the bushes, especially the tie bar bushes. The Superflex tie bar bushes have a locating spigot whereas others do not. I think the other problem is the colour of the bush doesn't mean anything. It would be great if the colour followed some kind of standard for the Shore rating. I am really pleased with the improvement with poly bushes front and rear. Admittedly this is not a fair comparison. It is not a comparison of good rubber bushes versus poly bushes but of worn out rubber bushes versus poly bushes!

Stephen

[Bill_qaz]

Phil posted some excellent info on bushes
viewtopic.php?p=675996&hilit=Poly+bush+hardness#p675996

[les]

Thanks Bill, my main concern was the difference in flange thickness, the ESM site shows in the rear spring kit regarding the rear shackles, a blue pair and a red pair, I want to know which ones are fitted to the chassis and which ones go to the springs. I’ll have to call them, see if they know.

[svenedin]

Oh I see. I didn’t realise that was your question. Let me see what photos I took when I used this ESM kit….

Stephen

[les]

Ok thanks Stephen

[svenedin]

I did find my pictures but they were no help as I could not see the bushes.

I know you have a van and I am not sure how that differs to the standard set-up

https://www.morrisminorspares.com/rear- ... e-p1238939

With the kit above this is by elimination:

The 4x blue bushes have to be for the rear top shackle mount point (in the chassis) because this is the only place 4 identical bushes are used.

The 8x red bushes are for the leaf springs (which have identical eyes each end and take 2x bushes, in each eye).

Does that sound reasonable? I looked at the van kit and it seems that there are 4x blue of the same size in that kit as well. I am assuming they are for rear shackle top chassis mount point as for a saloon.

Actually I am confused and it is clear that the van rear suspension is too different for me to be of any use here.

I found this diagram for the van rear suspension (it is interactive):

https://www.morrisminorspares.com/catalogue-i30


Stephen

[les]

You can see the bushes for the rear shackles, ( the ones far right and far left ) a pair in blue ( thin flange) a pair in red ( thicker flange) Which go where, —— blue fitted to spring end, or fitted to chassis.

IMG_3330.jpeg (170.46 KiB) Viewed 378 times

[les]

Yes maybe the blue go to the chassis, reds to spring. Thanks for help Stephen, I think van is the same at the rear fittings.

[svenedin]

What's confusing me is the larger diameter blue bushes x4 in your picture. On the saloon all the bushes are the same diameter. Are the spring eyes a different diameter at either end? What are the larger diameter blue ones for?

All I can say is when I did mine with the ESM poly bush kit I am pretty sure I put the blue thinner flange in the chassis. It should be obviously what is right and what is wrong because the shackles have to sit parallel and if the wrong bush is used they won't sit parallel

Stephen

IMG_9182.jpeg (2.84 MiB) Viewed 363 times

[les]

The large blue bushes are for the front of the spring on the van, there is a pin that protrudes from the chassis cross member, this is where the large bush slides over, followed by the spring then the second large bush, washer and nut.
Those plates you illustrate should hit the shoulder of the associated pin when tightened, the variation of the bush flange thickness has a bearing on the ability to achieve this pin shoulder to plate contact. Too thick and the bush is too hard to compress to achieve this said contact.

[svenedin]

Yes exactly. The shackle plates are sitting on the shoulder of the shackle pins but if the bush flange is too thick it would be difficult to achieve this.

Hope our debate about which bush goes where was not a waste of time!

Stephen

[les]

Not a waste of time Stephen. Picture of van front spring location.

IMG_0985.jpeg (200.96 KiB) Viewed 347 times

[philthehill]

The thickness of the flange on a poly bush is not dependent upon the colour or supplier.
I have several poly bushes of different colours and from different branded suppliers and the thickness of the flanges varies.
There is no dedicated poly bush for the chassis and no dedicated poly bush for the spring eye (the exception being the front spring eye of the commercial chassis).
The only parameters being the length of the shackle pin and the width of the chassis rail.
Fit the bushes to the chassis rail and measure the overall length between the flange faces. Fit the shackle plates to the shackle pin and measure the distance between the plates. Compare the two measurements and select the poly bush with the most suitable flange thickness.
When the shackle is fitted there should be stiff resistance (but not total resistance) to the shackle turning.
I have found that in some cases the poly bush has to be spaced with shims.

eye bolt shim.JPG (505.31 KiB) Viewed 324 times

The average flange thickness of the poly bushes I have is 4.5mm. The flange ranges from 3.5mm to 5mm.

[les]

Yes, it’s not as plain sailing as one is led to believe. I phoned ESM and it was suggested that their blue bushes go through the chassis and the red through the spring. Regarding the steel pins, the red (thicker flange) bushes, when assembled are wider than the distance from shoulder to shoulder of the pins, and as I believe the shackle plates should contact these shoulders, the red bushes won’t allow this, unlike rubber they don’t compress enough. A similar thing on the van front, poly bushes won’t compress enough for the castlated nut to go on enough to reach the split pin hole ! Poly bushes are not as clever as they sound. If I could be sure of the quality I’d go back to rubber, also they’re not as harsh, having more give.

[svenedin]

New springs from Jones springs, polybushes front and rear and 4x standard, refurbished Armstrong dampers and I would not call the ride harsh at all. From worn out bushes, springs and dampers it is actually much less harsh. A tremendous improvement as far as I’m concerned and I’m really happy with it all. It was a lot of work and rather expensive but long overdue.

Surely, in the Morris set-up the bushes are really there to provide articulation. They are not there to absorb energy in any significant way. That is what the dampers are for. I think that sometimes people fit poly bushes to a suspension system that is very tired and then complain that the ride is harsh. That would make sense because with new poly bushes the suspension movement is very directly being transferred to the dampers. If these are tired, the result is going to be a harsh ride. The same with tired leaf springs.

I went from a car that could barely go over a speed bump at all without major dramas to a car that feels very pleasant to drive although I still slow right down for speed bumps as the suspension is really not designed for those horrors.

Stephen

[svenedin]

Not a waste of time Stephen. Picture of van front spring location.
IMG_0985.jpeg

Thank you. That's a fantastic picture and now I really understand the differences with the van.

Stephen

[les]

Just an update, finished the bush replacement, both sides. Took me a while, being fussy. However I’m relatively happy with the end result. Mind you I ache now ! Anyone would think I’m getting old ——- oh hang on, I am !!

[svenedin]

Just an update, finished the bush replacement, both sides. Took me a while, being fussy. However I’m relatively happy with the end result. Mind you I ache now ! Anyone would think I’m getting old ——- oh hang on, I am !!

Only "relatively happy"? What's not to be happy about other than the aching?

Stephen

[les]

Well there’s always something that niggles a bit, I was still thinking of the variation in the bushes but like all things you can worry yourself silly if you let it. Must be nice for the folk that can say ‘sod it that’ll do’ —— but we’re not all built that way !!