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MG Midget and Sprite Technical - Shock absorber valves

I have a set of shock absorbers that appear to be in good order apart from some problems with the O rings on the front valves. Does anyone have a source / specs for these O rings?
Dominic Clancy

Very probably a standard size and material (nitrile rubber?). I don't know what size though off the top of my head.

I have the rear shocks off my car at the moment, let me see if I can figure out what size it is on the rears, I would have thought it likely that the front is the same.

Cheers,
Malcolm
Malcolm Le Chevalier

As it's an old British application I would have guessed they would be using BS standard O rings of which a list is here http://www.par-group.co.uk/sealing-and-jointing/o-rings-and-mechanical-seals/o-rings/bs-o-ring-dimensions/ . The list goes up in blocks of increasing O ring section size so you need to scroll down to see the larger thicker section choices such as the big seal for the valve body to damper casing. Once identified it should be easy to find a UK supplier of the sizes required. Regarding material Parker have an excellent O ring design guide which gives material suitability for the working fluid types http://www.parker.com/literature/ORD%205700%20Parker_O-Ring_Handbook.pdf . You may have to copy and paste that last link.

David Billington

To be sure, you are talking about the o-ring that seals where the valve screws into the body, right?

I have had a look at my rears, closest size match I can find in the kit I have is a 17 x 2.5. But it looks a tiny bit smaller and a tiny bit fatter, say a 16 x 3 or similar.

Malc.

Malcolm Le Chevalier

A problem with O rings is the number of standards around. A mate used to work in a truck air brake company and they used lots of O rings in designs so he was aware of the BS standard and DIN standard, but also a French standard which while metric was slightly different to the DIN standard. That came in useful when rebuilding the rear handbrake calipers on a Lancia Beta which seemed to have the French section O rings, the O ring wasn't in the rebuild kit so he requested some from the German part of the company as a sample in the appropriate EPDM material as being most suitable for brake fluid. A Lancia specialist I spoke to said he just used standard nitrile O rings from a standard selection pack which while not ideal seemed to work. As a static seal anything close is likely to be OK for the main valve to body seal and I seem to recall it get distorted quite a bit, memory vague on any other O rings in the damper valve as I ditched the levers arm dampers decades ago.
David Billington

This thread was discussed on 30/11/2016

MG Midget and Sprite Technical index

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