Overhauling Blue Fleet's Cannondale Lefty DLR 100

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  • Because I don't have enough to do I told Blue Fleet that I could repair his 2002 Cannondale DLR 100 Lefty 'strut'. Apparently it has sat under his bed for the last half decade after the Jekyll 800 frame it was paired with snapped.

    And so it duly arrived.

    The symptoms: it's completely seized. Not locked out. Seized. What's gone wrong? Who knows. Either the damper or the bearings are shot. or something more sinister. I suspect water has got in to it though and rotted the bearings and races. More on those, later.

    Anyway, I'm going to strip it down until I find the culprit and if it's repairable, so be it, and if it's not, in the bin it goes.

    This thread will document the process for shits and giggles.

    Link to full size photos

  • But first...a quick external clean.

  • ha ha brilliant, good luck to you sir. And ooof shamed straight away for it being dirty upon arrival, but thats how you mountain and cross guys like it right?

    I hope this has a happy ending.

  • Hah no shame in a bit of grime :)

  • To get into the Lefty's delicious internals the steerer and clamps have to come off first. You can't do this with the lock-out dial and damper cap in place so those need off first. The red rebound adjuster dial sits on top of all of this so that needs off too.

    It's press fit, so a yank with a pair o pliers and out it comes.

    The lock out dial is also pressfit, so a good tug and that comes off too.

    The damper cap has a bolt fitting but this one screwed off by hand.

    Next there's a plastic insert that sits above the damper proper- it's a loose press fit and drops straight out.

    With all this out of the way you can remove the clamp bolts and slide off the top clamp...

    Remove the frame bumper...

    Then remove the bottom clamp

    We now have a single 'strut' to work on.

  • For a complete overhaul the air filter and boot should be replaced.

    You heard me right: an air filter and a boot.

    More on these later.

    Filter is held on with zip ties. Snip snip.

    Once is slid away you can see the breather holes:

    You can also see the muck in the filter:

    Next the boot. That has small clamps held on with alen bolts

    And another stupid zip tie:

    With the zip ties undone you can slide the boot up and over the lower retainer collar and off the strut.

    Oh dear:



    I think I found the problem...

  • Again, balls:

    This is the view looking down into the strut with all the top-cap and rebound paraphernalia removed. The bolt like thing closes / opens the piston to enable hydraulic lock-out. The spindle above it adjusts the rebound speed. Below them both is a lock ring that holds the damper in place.

    Irritatingly I don't have the tool for the lock ring. I can buy the cannondale one, but it's only useful for forks of this age and is quite pricey.

    Know anyone who could machine me one?

  • Jesus H Christ its fossilised! God that looks grim, more than a bit of Brasso needed there then.

  • Hah, yeah. As suspected the bearings and races are most definitely gone. They can be replaced though. I'll drop Mendon a line and see what's available before I go any further.

  • This has also given me extra terror tremors about what other horrors lurk under my bed, I'm too scared to look.

    That tool looks pretty niche, I guess its not the kind of thing our average lefty owner is likely to have, and just the preserve of a dealer/mechanic. I'm not a member of any mtb forums but you think its worth asking around to see if there's any in circulation?

    Or ideally a friendly mechanic and owner of said weird tool will see this thread and applaud your heroic effort and want to see a Steve Austin style rebuild, if only we had the technology.......

  • Yes - it's a mechanic / dealer tool, and they only used that fitting for 2001-2002. All the others use the standard castlenut tool, that I have (doh!).

    If the races / bearings can be sourced I'll just buy the tool and get on with it.

  • Hey Howard, the parts are still available, but you'll likely need to cut the races down, as the "proper" lengths aren't made anymore, just longer ones.

    Bearings, no problem.

    Seals, no problem.

    Happy wrenching =:)

    Cheers, Craig

    Hurrah. Now to find the kidney tool...

  • In other news, good thing I thought to check the pressure before going further...

    Still got 90psi in it.

    Here's the lower leg cleaned up - yes, that's going to need some work.

  • Update.

    According to the excellent Craig Smith of Mendon Cycleworks USA KT004 is the tool I need. It will open up lefties from 2001 to about 2004, so not as niche as first thought.

    It's irritatingly expensive though.


    i. Buy tool, suck it up.
    ii. Get a similar tool machined
    iii. Bin the poor dear and give up
    iv. Find someone with the tool and borrow it

    I don't like iii - I hate the idea of throwing away something like this, especially as the air spring is still obviously functional. I like the idea of getting something machined to do the job, but I have a suspicion I'd need two tools machined which will end up costing more than the KT004. I like the idea of borrowing the tool, but I tried this with the Castle Tool for Headshoks and had no joy - and that's a more useful tool as it opens up pretty much any Headshok from the year dot.

    Balls. Guess I'll have to pony up.

  • Option 5: improvise a way to twist it with a couple of flat-head screwdrivers? Only viable if it's both robust and not too tightly stuck.

    Also, could you replace it with the modern part you have the tool for?

  • Yes - fudging it is another possibility. I have a super long & sharp pair of needle nose pliers that could be used to try this. However from reading around the general consensus is that it's likely you'll damage the parts in the process and non-consumable spares for this strut are going to be super difficult to acquire.

    It might be possible to replace the lock-ring with something easier to extract but the second part of the KT004 tool plugs directly into the damper cartridge body itself, so even if you were able to get it all out without the tools, getting it back together, and apart again in the future would still be onerous.

    In terms of replacing the innards with something easier to remove in future Cannondale actually designed the damper cartridge system to be swappable so in theory you can put a modern damper in an older lefty that requires only the one generic castle tool to extract. However around 2006 they changed the design to the point where modern dampers can only be fitted to 2006 or newer struts. I'm committed to the damper that's in there now, unfortunately.

    A final option would be to try and create the tools myself. In theory both parts of the KT004 are simply tubes with slots cut into them. The lock ring bit looks quite straightforward as the slots are small and the interlocking surface large - get a tube with the right dia. then cut the slots in with a hack saw. Unfortunately the interlocking surface on the second part of the tool are quite small. I could see it being possible to recreate it with a hacksaw but then it simply rounding off when any force is applied to it. And you'll need some force as the damper is screwed in tight and threadlocked.

  • ii. Get a similar tool machined


  • i - buy tool - secondhand here > http://www.cannondale-parts.de/epages/61­764971.sf/en_US/?ObjectPath=/Shops/61764­971/Products/KT004

    iv - borrow tool - asked on retrobike/mtbr/stw?

    vi - specialist - ask tony nunn at thumbprint tuning > http://www.thumbprinttuning.co.uk/

  • I can buy the tool from a shop down the road - that's not a problem. It's not like the dark days of Cannondale Europe - CSG are doing a great job. They even reply to email ;)

    I can ask around to borrow one - and then get a replica machined. I don't hold out a lot of hope though because I've tried that approach before for more common tools and had no response. But I'll give it a shot :)

    I thought about hitting up thumbprint. It's possible that he might lend me the tool and then I can get a copy machined. I'll drop him a line today, but I'd feel a bit cheeky in doing so.

  • i don't know what line of work you're in howard, but you may have something to offer so that it's not so cheeky


  • I could make his website work on an iPad. 100% flash - party like it's 1999.

  • Link to full size photos

    I dropped Thumbprint a line - waiting for a response.

    Trawling retrobike/STW/Bikeradar today for potential KT004 owners.

  • ^ Repped for dedication!

  • These are great 'forks'. As long as you have access to consumables - seals / bearings / races / boots - they should go on forever.

  • Ah - this is useful. Exploded diagram of how the KT004 works.

    Looking at the diagram, it's possible that should I be able to remove the lock-ring I might be able to use the supercastle tool I already have to unthread the damper.

    I've asked Craig at Mendon about this - let's see if he gets back to me and what he says.

    Edit: OK. Maybe not. It appears that what I assumed was a lock-ring is actually just a driver for the second part of the KT004 tool.

    Anyway, it looks like what ever happens I need to be able to get the lower up into the upper again which means freeing up those rusted bearings. I'm thinking of letting it sit in some plusgas or WD40 for a few days then giving it a whack with a mallet to free them up. Any other suggestions?

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Overhauling Blue Fleet's Cannondale Lefty DLR 100

Posted by Avatar for Howard @Howard