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MG Midget and Sprite Technical - 88G274

For some time now these top trunnions bushes have been coming through with a simple parallel outside dimension rather than tapered as original. End result is a short life due to contacting only at either end rather than all along the bush.

We have tried multiple suppliers (6 at least), but all the same design. In fact two different versions of the same design.

Has anyone found a source of correctly shaped bushes?
Paul Walbran

Poly bush instead?
anamnesis

Ballingalls have them - different part no.though

https://www.ebay.com.au/itm/263355059070?
William Revit

William, They look like lower trunnion bushes??
Bob Beaumont

Agreed.

These are top trunnion.

https://www.ebay.co.uk/itm/204197111532

Also on and ships to Australia.

https://www.ebay.com.au/itm/204197111532





anamnesis

Thanks all. Anam, from what I can see they are the same basically parallel bushes that we have been getting from all over. The main body should be significantly tapered to match the trunnion, as in this shot of poly version.

Yes poly is an option, but we seem to be encountering some poly which is failing very prematurely, quite aside from the cost question.
Paul Walbran

Agreed. I have some NOS ones which have a taper.
Bob Beaumont

Ah yes, I see what you mean now Paul. They don't look right. I didn't look closely enough.

As you say there should be a definite taper. As in this picture of one of my good used spares.

I can't see your pictures Paul. Is it just me?


anamnesis

Undoubtedly me! I nodded off before adding them then got confused. 😂
This was the one, but yours is better.
Paul Walbran

Sigh.
Failed again.
3rd time lucky.


Paul Walbran

Here's a pair from my NOS QH front suspension kit. Makes me wonder how these things are specified and if anyone does any QA on the resulting product, I think I know the answer to that last point already.


David Billington

Interestingly, in our shopping around we have found two different versions of the wrong one, same dims as each other but clearly different in other respects.
Paul Walbran

Paul

The bushes I posted earlier and incorrectly identified on here as lower bushes are in fact upper trunion bushes but an original earlier design
If you're after the flanged and tapered type then Ballingalls have them as well--

https://www.ebay.com.au/itm/265810467673?

Just out of interest you mentioned some polly bushes failing, We've had issues with them here as well, don't know the brand but they always seem to be red ones

If it's for your racer ,have you thought of having some sintered bronze bushes done for it-
Something like these-example only-not to size-

https://www.refast.com.au/smf2408-sintered-bronze-self-lubricating-bush-flan?
William Revit

Thanks Willie, I will follow that up.
The bushes that have failed have been purple. Most recent is an engine stay bush for an MGF. Fitted to customer's car in November last, arrived back this week with bush completely gone.
I am looking for stock. The parallel ones bear on the inner end and the flange with no contact in the middle. Can't be good for bush life.
Paul Walbran

Just checked the link, that's 8G621, which does the mgb top trunnion bush as well as midget inner wishbone.
Paul Walbran

Yep- but isn't 8G621'Z' the flanged type you're after.
I always thought the upper and lower bushes were identical. Can remember buying them in a set of 12 for a Midget to do both upper and lower and can't remember that there was any difference in any of the bushes in the kit-
William Revit

As usual the BBS gets me thinking - I have probably never seen or fitted a correct spec one of these, just the usual rubbish!

Anam mentioned a Polybush version, AH Spares sell these: https://www.ahspares.co.uk/austin-healey/sprite/suspension-front/top-trunnion-polybush-kit.aspx I guess the same query about if these are the correct profile would apply.

I wonder what Colin Dodds of Spriteparts sells?

Cheers
Mike

M Wood

Willie, that's an interesting thought. 8G621 is 7mm longer than 88G274 and iirc the taper angle is less, but shortened to the same length it's dimensions are better than the poor version of 88G274 now present. I will investigate further.
Paul Walbran

Willy

Upper and lower are definitely different on a Midget.

MGB upper are the same as Midget lower (inner).
Dave O'Neill 2

Cheers Dave -
William Revit

I dug out some genuine BMC old stock today. The lower is 7/8" long and the upper is 5/8" - but the most important difference is that the upper has has a rubber shoulder which stands proud and is backed by the rebate of the steel insert, giving an OD of 1-1/8". The lower by contrast just has a tube steel insert , and after the 9/16" tapered section it just runs parallel for the last 1/4". Hopefully the pics show the detail. If the top mounts in poly don't have the top hat of the insert then it's hardly surprising that they fail quickly. Looks to me like someone has just copied the shape of the part into poly without attempting to understand how the bushes function.






David Smith

David, from what I can see the top trunnion bush in that image isn't shaped like the genuine ones I remember all the way back to the early 80s at least right through to only 3-4 years back, as they had quite a taper, similar to the poly bushes in this image. (No doubt in recent years they were no longer genuine)

The problem with a parallel bush in a tapered hole is that it supported at two points and not uniformly. Result is more than intended compliance and reduced like. Good for sales, but not for their purpose.



Paul Walbran

Paul, I ordered the modern bush kit from MEVspares on ebay; the upper bushes are tapered like the originals in my last post ( the camera didn't show the taper very well, trick of the light and angle probably). However i can see two problems with the new ones; firstly the ID of the steel insert is larger and the special bolt is no longer a snug fit but has some slop in it. Secondly the inserts are made in thicker sheet and also protrude slightly out of the plain end so when a pair are fitted they abut on the inserts and need a good heave to get them to close up.






David Smith

Now the lower inners. The original ones are snug on the bolt and the inserts are the perfect length so that when tightened up the shoulder of the located washer fits into the hole in the mounting bracket.





David Smith

Whereas the modern pattern replacements are (like the uppers) a sloppy fit on the bolt, and the inserts are a tad too long so when butted up against each other the special washer does not cleanly locate in the bracket. A really good heave on the ratchet is needed to distort them enough to get the washer to close up onto the bracket, and it's difficult to ensure the step cleanly locates into the hole at the same time. Probably best to shorten the inserts with a file to get them back to the correct dimension.






David Smith

This thread was discussed between 18/04/2024 and 30/04/2024

MG Midget and Sprite Technical index

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