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MG Midget and Sprite Technical - Polybushes

One rear spring is now off, and my as my back is now goosed from removing 40 year old nuts, I am concentrating on the less physical stuff.

To that end, I have ordered a set of orange poly bushes - the 8 top hats and the 4 pads

I believe these are medium hardness - which seems fine, but....

What would be the difference between fitting all the bushes as opposed to fitting just the poly top hats at the shackle and keeping to OE rubber for the pads? My thinking is that the latter approach would retain the cornering advantage, and slightly soften the straight line ride.....thoughts

Secondly, greasing the poly bushes---would dab of silicone grease on the top hat bush on the outer mating face with the shackle be wise? The old rubber ones seemed to prevent the shackle flexing vertically freely....
Mark O

Mark,
When I did mine I used the poly spring pads and it did make a great difference to the cornering and nothing noticeable to the ride. Mind you my rubber spring pads were shot to hell!
I can't see what harm some silicone on the outside of the bushes will do. I recall smearing the whole thing pretty liberally. The only problem is knowing how much to tighten the up-bolts up by, as the pads keep compressing. I worked on advice from here which was "as tight as you can get them with a nine inch or spanner and then a quick tighten up everytime you have reason to be under the back of the car."
Seemed to work well.
Good luck with the rest!
Matt1275Bucks

Cheers Matt - I value the empirical advice over the theory any day. My OE rubber pads are also shot to bits - so comparison may be similarly affected.

Did you also use poly at the shackle?

Mark O

Mark,
I poly-bushed (surely not a verb!) the whole of the rear suspension and it did seem to make a significant difference. Some of this might be due to worn rubbers and some down to the placebo effect of having spent money and a few hours under the car swearing at it (been there done that with shackles and the fuel tank!), but at least I know its all new now and should hopefully last a good few more years spirited driving.
Having been brought up in Aberdeen too, I still have open wallet aversion! I envy you midget motoring on the great driving roads in the area but last time I was up I was shocked at how much development around the city there had been since I left in the mid '80s.

Matt
Matt1275Bucks

I've not seen orange ploy bushes so don't know about them but with others you get small sachets of whatever is required for installation or instruction of what to do/use on packaging or on their web site
Nigel Atkins

Matt

Oil industry still grows apace in Aberdeen. Plenty of jobs and money still around up here to serve not only N Sea but further afield. Corresponding increase in traffic, houses etc, and still the council fails to build the necessary by-pass - despite BP offering to pay for it 30 odd years ago. However that is the subject for a tiresome rant, so yes, out of the city some glorious roads and virtually traffic free most of the time - was certainly very satisfying this summer.

Nigel- bought the bushes via Fleabay from a Mini parts e-shop. They look the job, but no grease supplied.
Mark O

Mark, Its not the City Council refusing to build the bypass - but a series of legal challenges by influential objectors. Worms in a tin can comes to mind!
Guy W

Guy

It is indeed a can of worms, but I do believe that at the time the offer was made by BP to fund it - or at least some of it - the way was pretty clear to simply get on with it. As time went on, folk became much more - objectionable - for want of better words, and progress was indded slowed to allow the lawyers involed to amass enough funds for their holidays in Barbados.

That said, work has now started, so I look forward to driving on it in about 20 years time.
Mark O

Mark, once the big yellow machines arrive, it is well on its way to completion. You are almost there! Unless of course its an Edinburgh Tramway! Generally with big infrastructure projects the pre-construction phase these days usually represents around 80% of the total project timetable. Far too many reports, investigations, assessment, QI's, EIA's, EU approvals, consultations, reviews and more reports are required!
Guy W

With the quality of rubber bushes being so poor nowadays I'd see Poly bushes as a very viable alternative. You can often be offered a classic or sport option, the sport offering a slightly higher shore rating.
We researched the market about 15 years ago and became a Superflex agent several years ago. I have yet to see a better bush, and these come with the correct white grease for lubrication.
One thing to remember , as will all types of bushes is to only finally tighten them up when the car is on its wheels and not still on the axle standds.
Also several bushes are similar between car marques and can be offered cheaper by non specific traders.
This is the range we stock for Minors, but we will soon be holding stock of Midget specific items.

http://www.jlhmorrisminors.co.uk/store/index.php?act=viewCat&catId=21
J L HEAP

Mark,
Aye they were talking about a by pass certainly by the early eighties if not before from memory. Intrigued it's now starting. Anderson Drive was busy enough in my day. Are there still roses up the middle. Somehow I doubt it!
What's the by pass routing ? I presume it's a fair way west and where will they cross the Dee?

Matt1275Bucks

JL Heap - Yes indeed. I believe orange has a shore rating of 75 - about medium - so fine with me. Duly noted about tightening up until weight applied.

Matt - Anderson Drive a nigthmare - naturally - and yes, still fragrant in the summer evenings. The one thing Aberdeen City Council does excel at is the glorious work of their flower arranging department. Duthie Park now magnificently restored

Full details of bypass on web - but yes I believe anotherr bridge over the Dee out W somewhere near Milltimber is proposed - much to the ire of the millionaires living there.

All that said, it remains a fine place to live and work. Quality of life and all that.....
Mark O

Always try and source heat cured bushes as they will have a much longer life cycle. Shore ratings can be a bit misleading in some cases, partly due to the physical sizes of bush for a given use. For example a MK1 Escort has vastly larger shackle bushes than a similary weighted Morris Minor. To compensate for the smaller working surface area of the smaller bush, manufacturers will increase the shore rating, ie Escort rating 75 Minor 95 shore.
J L HEAP

The name polybush has become something of a generic term, like hoover for vacuum cleaner. So beware what you buy or actually get.

A few years ago I bought a full set of blue Polybushes from a reputable supplier. When they came they were all neatly packaged up in sets for the different parts of front and rear suspension. I went ahead and fitted them all, but 2 of the 4 pairs for the front inner wishbone pivots split and crumbled as I fitted them, although they all looked identical. I then noticed that 2 of the plastic bags were differently marked, and didn't carry the same Polybush (capital P) logo and labelling. After a bit of to and fro with the supplier it turned out that they were out of stock from the Polybush manufacturer (in their home town) so had bought in extra stock from elsewhere. It was this other source of polybushes (small p) that were rubbish.

So, be warned. They may all look the same but certainly a while ago there were some rubbish copy ones circulating.
Guy W

Chaps

Duly noted re polybush quality but rather like the springs themselves, very diffcult to spot beforehand. Mine are stamped with the correct part number - which I feel is encouraging - and dimensionally at least, appear to be identical to the OE rubber ones I have just removed.

I would also add that again, as per the springs themselves, poor quality is just as likely to occur when purchasing from alleged reputable larger suppliers as it is from when purchasing with a bit of care from certain auction web sites or the internet directly. Indeed, I would imagine that in many cases the supplier is just the same.
Mark O

Why do they have to be such garish colours? Whats wrong with black , hate the thought that I may have yellow / Purple / Orange / Blue bushes over the car . Who does good quality Black bushes?
R Mcknight

I've gone the other direction.

Top hats are poly and the pads are alloy!

I just figured as the spring and shock are mounted in rubber the transmission of noise etc should be stopped there.
And guess what .... It works!
Just not realy sure what kind of life you get from the alloy pads but so far so good (3000miles and counting)
Onno K

what are "top hats" and "pads"?

If you have put aluminum in place of rubber where the axle is clamped to the springs, the concern would be for spring fracture at the edge of the aluminum pad.


Norm
Norm Kerr

Norm
The top hats bushes are the ones in the shackles and the pads are indeed the ones between axle casing and the spring.

As said it is an experiment but I don't think spring fracture is a real high risk as it isn't a particular hard alloy.
Onno K

I see Moss still lists Nylatron spring pads, which would be harder than polyurethane but softer than aluminium: http://www.moss-europe.co.uk/Shop/ViewProducts.aspx?PlateIndexID=1136

And I have just found this in a thread from 2011: Deborah Evans responding to this comment from Norm Kerr "I can see why racers use aluminum blocks here. Would probably make for a harsher ride in a road car, but a lot less "guesswork" for a racer." [the guesswork being a reference to tightening the u-bolt nuts against rubber]

DE: "They take out any movement of the axle here. The difference when I upgraded from Nylatron spring pads was quite remarkable!"

Jonathan
Jonathan Severn

This thread was discussed between 30/09/2013 and 11/10/2013

MG Midget and Sprite Technical index

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