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Front shock absorber bottom bush


Craig

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Can anyone confirm the diameter of a standard front shock absorber bottom bush for a Herald/Spitfire? I have measured the AVO shock absorber, and it measures 25mm / 1", but the replacement bushes I have are only 22mm or 7/8". Cheers Craig16550422223451578704413983322890.thumb.jpg.c496441d5f04e8ff60786a994bd1a49a.jpg

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I can’t help with the “normal” bush diameter, but I can tell you that the AVO design will inevitably and repeatedly fail due to insufficient area to spread the load and too much rotational movement in this application. It rapidly shreds the bushes.

I gave up after 4 bush replacements in about 20k miles, by which time the dampers themselves were shot anyway.

Best path IMO is to bin them and fit something decent. However, if the dampers themselves are still good you could convert to a rose joint (one of the reasons the original bush design is so compromised is that the lower ring is also machined to take a rose joint) or perhaps hunt down a metal cased bush which is a moderate interference fit in the lower ring.

Nick

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Thanks Rob and Nick. I will persevere with the AVOs for now and see if I can get replacement bushes from AVO. The design of the bottom bush arrangement is a bit pants. I wish I had bought Konis now. Definite case of buy cheap, buy twice. 

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18 minutes ago, Craig said:

The design of the bottom bush arrangement is a bit pants.

It’s utterly unfit for purpose. It may survive in a vertical install where it doesn’t have to accommodate any rotation, but not here. You should insist that they send you a set FOC as punishment!

Konis are much better in quality and performance respects. The lack of adjustable spring seats and external rate adjustment is a loss of convenience though.

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I met a local Vitesse owner yesterday who had the same issue with his AVO shock absorber bottom bush, and he managed to improve the situation by fitting a rear leaf spring eye bush (part number C8939) into the shock eye cut down to the required length. Just need to find a spare bush and confirm the outer diameter. Good idea / bad idea?

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Good idea.  I did exactly the same on my Spitfire and it completely eliminated the clonk you get when the AVO plastic bushes wear.  The new rubber/steel-sheathed rear spring bushes have been on there for years now and are still working well. The bush is the correct diameter but is a bit too long. The tricky bit is cutting them to correct length and keeping the cut end square, although I just parted off the end of mine in a lathe. I realise not everyone has access to a lathe so needs to be done carefully with a hacksaw and vice.

Edited by sparky_spit
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