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MG Midget and Sprite Technical - Rear Shackle Polybushes

Hi folks, I'm after advice from the collective again.

Do I need to fit crush tubes with poly bushes in the rear shackles?

it's a 1975 1500
N Broomfield

They don't come with any and the rubber ones don't have them
mark heyworth

Not needed because the shackle pins are stepped. The step acts the same way as a crush tube.
Paul Walbran

Aha!

Stepped pins, I haven't yet taken the shackles off so have not spotted that. The instructions speak of crush tubes but the websites don't mention them and I can see that there is a step in the inside tube of the bush with cross hatch grooves, for the grease I guess. Obviously the stepped pin fills this and is directly against the greased cross hatching. Marvellous, I'll get cracking tomorrow. I've read in the archives of having to drop the tank to get the shackle pins out sideways, or taking the whole shackle mount off. My shackles appear to be mounted to slide to the outside, nuts on the inside, so hopefully I won't have that issue. I am very wary of undertaking jobs only to find that I need to do something else first or need a special tool or part. I've stil got to free the jammed adjusters to replace the rear brake shoes/drums.

I got two sets from Midland Sports and Classics to try out.
A set of rubber bushes and a set of Autobush polybushes in Deep Purple (I'm sure there's a pun there). I could not see a choice of colour so I don't know whether these are soft or hard, they seem very close in pliability to the rubber ones, if very slightly stiffer.

I'm not racing it, yet, and I don't want too harsh a ride. But I can't see that changing the rear shackle bushes will have that much effect, I'm not planning on changing all bushes, although I am planning on a 3/4 inch antiroll bar from Frontline and that can be done with polybushes.

There's been a lot of talk on the forums that polybushes make for a harsh ride, it would be good to know where this harshness is mostly evident, front or back. I see there are 4 maybe 5 points at which polybushes can be fitted; antiroll bar, wishbones, spring pads, rear shackles and maybe front leaf spring mount?
Does anybody have any experience, an I'm sure there's somebody, of which point affected the harshness the most? My guess is the wishbones.

Take care
Have fun
Don't die
NigelB
N Broomfield

First, why do you think you want a 3/4" front ARB, whatever size don't get it from shacks-of-sh*te conmen, give a really decent chap a ring and ask his advice on front ARB to suit your set up and needs. You might want to add end stops to the uprated ARB too.

Kim Dear - Magic midget - https://www.magicmidget.co.uk/shop?Collection=Suspension

If you have a bigger ARB you will need to beef up the chassis legs mounts somehow, various methods in the Archives here, or the mounts will pull - guess how I know for sure.

When they (who, those on FB) say polybushes make for a harsh ride which polybushes and when, yesterday, many years back, they're not confusing them with race use or other materials bushes for race cars.

Different manufacturers use different colours and perhaps colour codes to each other often, if they offer different uses there might be a colour range, I don't know Autobush if they don't say different I'd assume they are for ordinary road use and suitable stiffness/harshness, but that's just an assumption, ask the manufacturer to be certain.

MGOC Spares used to do two different colours, IIRC I had the less stiff/harsh of the two and they just seemed a bit more bouncy than the standard rubber bushes that were on before.

I switch again to Super Flex without bounce or harshness over 12 years ago, I assume they're made the same still but you'd have to ask them.
Nigel Atkins

My 2 cents worth-
The bushes will be fine, you might, might just feel it a tiny tiny bit more jiggly but you probably would with new rubber ones compared to the old ones anyway----The colour coding thing has gone out the window unfortunately as some manufacturers started selling random colours to suit their brand--so a proper coded red set for example might not be the same as red ones from someone else who only sell their red ones--some makers still adhere to the coding system but you just never know who's who

3/4" bar is perfect for a midget but as Nigela noted you will have to beef up the chassis mounts for long term life and again your car will feel stiffer/jigglier with that size bar but great choice in my view, perfect size

willy
William Revit

"Take care
Have fun
Don't die" ?

There's optimism for you. 😅
anamnesis

Oh, bugger I missed it was a 1500, still a 3/4" on standard and possibly worn standard front single arm dampers and soft standard possibly squiggly springs, standard tyres and wheels, on a standard car just for road use, sounds a bit OTT to me.
Nigel Atkins

Maybe it's not going to be standard for long.
N Broomfield

Fair enough. All the more reason to talk to decent types like Kim Dear at Magic Midget.
Nigel Atkins

I have polybushes on the front - replacing all the rubber ones. The main adverse effect is more steering kickback, especially on potholes. I got used to it. Steering is generally a lot more precise. I haven't fitted them to the rear, as the ride is quite hard enough as it is.
Les Rose

Even standard, I find Spridget steering pretty precise, even when worn. When I fitted the mk1 version of the FL tele damper kit, with the extra neg camber, it was very twitchy and precise. You get used to anything quite quickly, but anything that makes pot holes more noticable, is definitely something to avoid thee days I reckon. At least the rubber absorbs the impact a little more, and hopefully reduces damage to the k/pin bushes and outer fulcrum/bush in the wishbone.
anamnesis

Gents,

I suppose I'm looking for the line between precise steering and twitchiness, handling like a sportscar or handling like a boat, too hard or too soft, etc etc. I just don't want to waste money doing the front suspension or rear spring front mount to find that it is a step too far.

I think I'll go with the poly bushes on the rear shackles at the moment, report back and take it from there.
N Broomfield

This thread was discussed between 31/03/2022 and 06/04/2022

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.