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A guide to removing, dissassembling and reassembling a Cannondale Super Fatty M Headshok
Please note: I (Sheldon Brown) did NOT write this. I have not worked on one of these forks.
If you get in trouble, don't bother asking me for help, you're on your own!
I'm posting it in hopes that it might be useful to some folks, but I can't give you any assurance of how the job will come out if you choose to attempt it...
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Total cost for me to regrease, put a boot on, install new needle bearings and firm ride springkit and purchase any tools I needed: about $70. It took me about 8-10 hours in total to disassemble, reassemble, disassemble and reassemble again (includes thorough degreasing and cleaning). Admittedly, I do have some tools already, but everything else I needed I use in the general maintenance of bikes and is not Cannondale specific (e.g. hammer, Slick Honey grease, Pedros degreaser, etc).
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http://www.fastglass.net/bike/headshok/repair.html (also has Cannondale technical diagrams in the archive. This was the site that helped me the most -not least because of the clear directions but also great photos. On the downside -and rather worrying for anyone reading it -it does not include reassembly instructions, nor the disassembly of the bearings and races). http://www.bikeparts.com (has some Cannondale Headshok parts as well as proprietary tools such as the castlenut tool ~$35)
http://www.cannondale.com/bikes/tech/headshok.html (Cannondale's own documents for Headshoks)
http://www.cyclingforums.com/showthread.php?t21400 (thread on Headshok disassembly)
http://forums.mtbr.com/showthread.php?p=1332068t (another thread on Headshok disassembly)
Some of the common themes I found in the message boards are:
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Another side note here: find a clean box to put parts in. I wish I could practice what I'm preaching here, but alas, I can't tell you how many times I've put a part down, and the "Small Part Pixies" come out with their magic dust and thieving grubby little hands -spiriting the part away right from under my own eyes. Putting the parts away safely makes it so much easier -I just really wish I could apply that myself!
You should now have the fork in your hands (with brakes removed or protected, right?). The next step is to secure the fork so that you can work on it easily -remember, I said there was only one of me and it can be a one person job:
OK. It's at this point I can proudly proclaim this was an original idea of mine. So much of the stuff I've posted is purloined and gathered from other links, but this one is all my own, so I'm "dead proud" of this. You can use the ends of the zip ties to jam down between the tops of the inner races and side of the tab on the race retention clip, forcing the race back and away from the race retention clip tab. If you do this with two adjacent races, you can then use the flat bladed screwdriver to push up the clip and remove it. Using this method, it took me all of five seconds to get the clip out. A word of caution here: I'm guessing that if you break the retention clip, you could be in trouble, so be gentle. This is also another advantage to using the plastic zip ties as it is less likely you'll brea`k that clip using them.
OK, back to my little cautionary disaster story: I had those three sets of parts described just as above. I put down the outer steerer tube with inflated inner tube on my workbench to start degreasing and cleaning the bearings and inner races. Suddenly, there was a huge "POP!!!!" and then the sound of tinkling glass. My god, someone is shooting out the basement window! No.....the cut off inflated inner tube had split open, now looking like a forlorn floppy black rubber banana skin, and the outer races were randomly strewn inside the steerer tube. I said "Oh dear" and then added other far less than parsimonious words of the English language.
If you recall from my description, I had about 15cm of inner tube extending out of the steerer tube, and when I had pumped up the inner tube in my ardour to secure the races...... well the top bit had deformed grotesquely because of the air pressure, which of course had no tyre wall (or steerer tube) to help contain it. So here's my lesson learnt: use a lesser length of inner tube (about 10cm), and have as little protruding out of the top as possible -this way, the inner tube should not burst. Also, don't be over zealous with the inflation. So, my dilemma now was I'd royally screwed up the order of the outer races. How could I put them back together again in the right place and orientation? All I can say is that in the end, I tried looking at marks on the races and matching them up to marks in the steerer tube. Honestly, I'm really not too sure I put them back in the exact same place, but what I can say is that my Headshok is smoother now or is as smooth as the day I bought the bike. I suppose the moral of the story is that even if you do lose the positioning of the races, don't give up, it's worth guessing and using a bit of detective work to hopefully reassemble them in the right way. And even if you don't put them back in the original places, it doesn't mean the Headshok won't work.
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My experience with this: remarkably, my first re-assembly I did went like butter and I could not resist letting out a whoop of exhilaration and complete triumph. I had no problems at all, and in the end this process was mere seconds in doing. Interestingly, the next time I did it when I was installing new bearings, my outer races slipped, and I had to start again -and of course, now everything had a load of grease on it too which made it a little more difficult.....I uttered a more fitting "D'oh" per Homer Simpson. Still, even so, it only took minutes in total. I put this down to my liberal and very enthusiastic use of electrical tape to secure bearings and races, as well as a gentle squeeze on that inflated inner tube to help secure those top outer races.
Interesting Super Fatty M note here: this connection from the rod to the aluminium cap became loose on my fork when I originally got it. I believe it occurred when I was trying to preload the spring too much, and I think it effectively forced the rod to turn clockwise (as I was looking down on it) thus effectively unscrewing itself from this aluminum cap. Maybe I should have used thread lock on this, I'm not sure. But I'm confident it's tight enough to not have this issue again, coupled with my new knowledge of the mechanical internals.
http://www.cannondale.com/Asset/iu_files/112495_Headshok_Fork_(up_to_2001)_Migration_Check_ Procedure.pdf If you have bearing migration.... what can I say.... start again!
I hope this post has helped. I wish it had been around before I started on my own Headshok servicing as (and I think you can tell) it was a learning experience for me as I went along. I've ridden the Jekyll since, and the fork feels fine, but of course, it may be I've done something terribly wrong -hopefully not -but would welcome any feedback or comments. One last thing I know I did do "incorrectly": you may pick up from the photos that the vent hole is positioned on the left hand side of the fork (a product of my exploding inner tube in that I lost track of it's relative position) -I believe it should it placed to the back of the fork. Since I tested it and it seemed to work (i.e. the boot isn't ballooning out with air pressure!) I'm guessing it's OK and I can hear the air being forced out..... so I made the decision to leave it as is.
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Please note: I (Sheldon Brown) did NOT write this. I have not worked on one of these forks.
If you get in trouble, don't bother asking me for help, you're on your own!
I'm posting it in hopes that it might be useful to some folks, but I can't give you any assurance of how the job will come out if you choose to attempt it...