Rear suspension leaf spring bushes

[canuck]

In my time under my car I planned a refresh of the spring rubber bushes. I see signs of cracking rubber but after 15 years of duty not so bad. 

Listening to alot of chatter about poly bushes, their inherent qualities of fit, long life, good ride quality,  etc.  I bought a set a few years ago. 

I decided to compare these Poly bush to OE type rubber bush,  and notice that perhaps these are not as 'proper' as they are made out to be?   

The factory parts list calls up the two bush for the front pin and the 4 bush for the shackle as same part number, #ACA5242. 
The poly kit I have on hand, contains two Purple colour bush for the front pin and four Red colour bush for the shackle. These are differnt size bush, as well as to the OE rubber. I show the flange thickness.



A check fit of the Poly to the shackle doesn't instill confidence.



I understand well the function of the Rubber OE type, snug and flex versus simple fit and pivot of the Poly.  I show this below. After this check fit I think OE type rubber the best option going forward.



The caveat to the rubber type, I have read, is their short life due to poor rubber compound? I discovered there is a new improved version of the rubber compound used for these bush promoting longevity? 

www.morrisminorspares.com/rear-suspension-axle-propshaft-c87/rear-suspension-c89/rear-spring-shackle-bush-high-quality-natural-rubber-4-per-spring-p831378

Have any of you recently fitted new bushes? poly or rubber? regular rubber or upgraded rubber?

Thanks


Bruce

 



 

[vue from the north]

didnt do the job myself got mr gargage to do it after an MOT (the poly ones had gone after 20 years of use / wear)  on the front replaced the lot i bought the green ones off ebay uk& the job was done ok stangely the backs were ok last MOT & have been on as long as the front 1st set 

[ozieagle]

Hi Bruce,

Remember that the rubber bushes need to be longer, so when tightened they compress, to jam in the holes. Poly doesn't need to do this.

Herb

[canuck]

Herb,
Thanks for this. 
Yes you are correct, my 3rd photo shows the compression of the OE type rubber bush. I think this is preferred?

The dimensions of the Red colour Poly bush show that the flange will be doing most of the work once bolted up to the leaf spring eyelet. I don't think this a good thing.   
Remember that this pivot pin has a fixed/precise distance between the shackle plates.



The Green colour bush kit Tim posted above shows all bush to be the same . Although the factory parts list calls up all 6 of these bush to be the same, this Poly kit is supplied 4 of Red colour and 2 of Purple colour.  The Purple colour bush is intended for the front pin application, and is a tighter fit, this I understand. FWIW these Purple colour bushes do fit the rear shackle pin length much better, do join in the middle, all due to the thinner flange.     Note: I haven't fitted these to the car yet. 

Makes one wonder if anyone from the Poly supplier has fitted these bush to a car prior to putting on the market.   

Salut
Bruce

[canuck]

I am still 'putzing' about because I am waiting for some other bits to arrive.

So down the rabbit hole I go.
We are familar with the expression,  'an idle mind is the devils' workshop'? So still being puzzled by these rear spring bushes, I decided to procur the 'new' true rubber bushes, #SUS720MMC  from ESM Spares.
 


Umm wouldn't we know it. These bush differ dimensionally than the OE 'old' rubber bush. The OAL =0.900" the flange = 0.145".

Consequence and as expected these 'new' bush don't compress as much as the OE type. I show this below.



I don't know the effect until I fit them but thought I would share this all the same.

Salut

Bruce



 

[kiwimc]

You've listed the flange diameter Bruce.  For interest can you give the main diameter?

So if I've got it correct, originals grip the eye from within, the shorter or poly bushes squeeze it between the two flanges?

J

[canuck]

John,
I think you are right, actually the dimensions shown is the thickness of the flange (s) not the diameter.  Apologies.

The poly must rely on the flange for cushioning the flex, where the rubber rely on torsion of the compressed bush.

I have a while before I assemble all this. My current thinking is I am in search of a 'metalastic' bush for the front eye. Many contempories of the Riley were fitted this way. 
If not able to find a suitable one I will install poly on the front eye and rubber on the shackle plates. 

B