Extended Top Fork Bush Mod.

I decided to fit the RGM extended (2.9" long) top fork bush kit (along with the 'Lansdowne' adjustable fork damper kit,-and more on that later) to replace the much maligned (by some!) Covenant conversion kit floating sleeves, just to see what the difference (if any) there actually was between them, as extended bushes (or extra sleeves fixed below the bushes) are supposed to act as a hydraulic buffer to prevent the forks topping out, and it has been assumed that Norton got it wrong, because the original bushes are not long enough to cover the stanchion restriction holes as the forks approach maximum extension, and there have been those who say that the floating Covenant sleeves just can't work.

So I will report that these RGM extended top bushes appear to do ABSOLUTELY NOTHING WHATSOEVER to control the action of the forks!

With SAE10 oil (as recommended by Lansdowne) and the Lansdowne rebound damper setting backed right off, so as not to mask any 'buffer' action the bushes may have, I can say that there is no apparent buffer action at all, and the forks can be made to top out quite hard at each rebound.

I may try some SAE20 oil later to see if that makes any difference, but I doubt it will?

So.....is this whole extended bush/fixed sleeve/floating sleeve buffer stop idea something of a Norton myth after all?

Very interesting. How do the floating sleeves compare, using the same setup?

Debby

debby said:

How do the floating sleeves compare, using the same setup?

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I have no idea. As I have not used the Lansdowne dampers with the Covenant sleeves, and I am reluctant at this time to have to strip and rebuild the forks again just to find out.

Since fitting the Covenant kit some years ago, I always considered that the floating sleeves did do something to assist the original dampers to stop topping out (as I couldn't make my forks top out after fitting them) but as you may have read here previously (or search "Covenant") others have had an opposite view that only fixed sleeves or extnded bushes would work, but apparently, they don't.

LAB ,
I am suprised you've found the extended bushes didn't work for you, they certainly do on my Mk3. I've recently fitted a pair to non-covenant Mk2a and they've worked perfectly.

Perhaps there's a mis-match here; Longer travel dampers that use SAE10 oil, that Lansdowne say don't need the hydraulic stop because they're always in oil, and with the hydraulic stops that require a minimum of SAE20 oil to work.

I'm sure you'll resolve this irritation.

Cash

cash said:

I've recently fitted a pair to non-covenant Mk2a and they've worked perfectly.

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I could say that mine also work perfectly-with the Lansdowne rebound damper adjusted to give adequate damping, as it is the damper that's then acting as the buffer stop.
What amazed me was that with the rebound damping adjustment completely backed off, the extended bushes were having absolutely no affect as a rebound stop. It could just be that SAE10 oil isn't thick enough, but I would have expected at least some slight amount of buffering action even with SAE10? I don't have any SAE20 handy at the moment (and Halfords didn't have any) so this is something I will have to try.

cash said:

Perhaps there's a mis-match here; Longer travel dampers that use SAE10 oil, that Lansdowne say don't need the hydraulic stop because they're always in oil,

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The Lansdowne dampers I fitted are identical in length to the originals, and do not appear to have any longer travel than standard dampers, although I'm sure they could be ordered with longer travel, as they are custom made, and once adjusted correctly the topping out stops, but of course this is due to the action of the damper, and not the extended bushes?

hi lab, do you have a link to the lansdowne dampers or anywhere i can find out more info thx

chris plant said:

hi lab, do you have a link to the lansdowne dampers or anywhere i can find out more info thx

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I intend to open a new topic about the Lansdowne (John Bould) damper kit shortly, but until then, here's some info:

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... 3D1&_rdc=1

hi lab,thx for that,they look promiseing,and compared to other damper mods they are reasonably priced,looking forward to your topic thx