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  1. #1
    CTB
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    Custom Fox Float Shock Install on 4-Banger Pics

    Hi all. I'm not sure if anyone cares about these bikes anymore, but I thought I'd share my latest project.

    I bought a 2000 4-Banger in May and absolutely love it. What I didn't love was the 2000 SID fork that leaked and flexed, and the SID Dual Air that started to leak as well, so I decided to upgrade both units. Upgrading the fork was easy - all it took was cash. The shock wasn't so easy due to the special mounting system of the 4B

    Below are the results of many hours of fab work and mooching some CNC time from a friend. I now have a 2004 Fox Float RL on my bike, and I have the head-angle adjustment like the earlier coil version of the bike had, with I2I range of about 133 to 146mm (5.2 - 5.7").

    The shock is from a 2004-ish Cannondale Jekyll, which used a trunnion mount. This shock also offers 1.75" of travel (I measured it to be 43mm/1.7"), so according to my analysis (and help from the Linkage software package), I've gone from about 4.1" to 4.7" of travel with this shock. Also, should I decide to do so, this shock can be Pushed in the future if I like it and my design holds up.

    I've only ridden it around my house a bit, but so far it feels like a nice improvement over the SID (which I was never fond of). Now to see if my design holds up under abuse...time will tell!

    Enjoy the pics.













    Last edited by CTB; 10-20-2008 at 01:10 PM.

  2. #2
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    All I can say is -- Beautiful!!!! I'm on a sid and I think it's a great improvent over the Deluxe...the frame feels great with a shock that ramps up at the end of the stroke. Well done.

  3. #3
    CTB
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    Thanks, Jomamad. I've never ridden a 4B without an air shock that builds, but I will in the future as I have another one on the way:



    It'll be interesting to compare how the two feel relative to each other. I'm also looking forward to seeing how this red one feels with slightly more head angle. This shock update was still cheaper and more fun than getting a whole new bike, assuming my design doesn't break.

    Gotta keep these vintage bikes on the trails!

  4. #4
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    both your 4Bangers are looking sexy!!! congrats on the CNC work!
    '11 Jedi
    '01 Straight8
    '01Rocket88< ran over it.. always do a full walk around!
    '00 Homegrown

  5. #5
    CTB
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    Thanks, shwinn8! I don't yet have the HG - it'll be shipped hopefully around Thanksgiving. I'm looking forward to trying it out and seeing how it compares.

    First ride of the new shock should be tomorrow if all goes well...

  6. #6
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    I hope you made some extra trunnion mounts for me.

    Looks very nice, have been considering getting one made for a while now. Currently riding on the basic coil shock, and have a Sid I was going to try to save weight and get more adjustments.

  7. #7
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    did ya get a chance to look in to Risse Racing? there 4banger specific Jupiter 5 worked awesome for me! i haven't ridden a rear air suspension before, how is it on bigger drops?
    '11 Jedi
    '01 Straight8
    '01Rocket88< ran over it.. always do a full walk around!
    '00 Homegrown

  8. #8
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    Quote Originally Posted by shwinn8
    did ya get a chance to look in to Risse Racing? there 4banger specific Jupiter 5 worked awesome for me! i haven't ridden a rear air suspension before, how is it on bigger drops?
    Those shocks are nice, but not cheap. Worried that my frame will crack after spending a pile of money on the shock. Anyone have a good condition 19" front triangle to sell me?

    Have been hoping to buy a cheap used 2" stroke Fox coil shock and get a trunion made for it. There was a Rock Shox on ebay yesterday, but the guy wouldn't ship it across the border.

  9. #9
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    Good scouting work on that. Nice job.

  10. #10
    CTB
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    Quote Originally Posted by Baulz
    I hope you made some extra trunnion mounts for me.
    Heh, no, I didn't, but I do have the CAD data for the part.

    Quote Originally Posted by shwinn8
    i haven't ridden a rear air suspension before, how is it on bigger drops?
    I'm an "in the seat XC" guy, so I don't do bigger drops. Probably not the strong suit of a 4" air bike, though.

  11. #11
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    I rode the bike last night for the first real test ride. I'm very happy with how it went! The shock is a nice improvement over the SID I had on there, I used the full travel of the shock twice, and nothing fell apart. I'll check all the bolts tonight to see if they retained their torque. Also, the change to the head angle dialed the handling in to something I like much better. It was a bit twitchy before, but now it is very nice. Woo hoo! A 4B with modern legs rides pretty nicely!

  12. #12
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    I have a sad update for this one. Today my uber-trick setup failed. Happily it wasn't while I was riding it, but rather when I was checking all bolts on the bike to make sure they were still tight. I took my first ride of the year earlier this week after completely rebuilding the bike, so I wanted to check that the fasteners were at torque specs. Sadly, when I checked the shock bolts, one of the sides had stripped-out threads.

    It's back to the SID until I can come up with a new idea. I'm very bummed. I figured this day would come, but I hoped it would have been farther in the future.

  13. #13
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    How about a Helicoil?

  14. #14
    CTB
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    There's not enough meat in there, I don't think, but it's one idea I'm looking into.

  15. #15
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    sorry to hear this, can you post the pic of the thing after it failed to see it?

  16. #16
    CTB
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    It looks just like it does in the pictures at the top of this thread, but now one of the small holes on the side doesn't have any thread in it for the bolts that go through the carbon arm to thread into.

  17. #17
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    I'm thinking it's going to keep doing this due to the side loading of the shock. It really needs a through bolt, which is not possible in this case.

  18. #18
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    Quote Originally Posted by CTB
    There's not enough meat in there, I don't think, but it's one idea I'm looking into.
    Use a time-sert instead. It's a solid threaded bushing and you can bond it in place by thinly spreading JB Weld on the threads before threading it into place. This way the force on the threads are much more evenly distributed and you're threading into a steel insert, not aluminum.

  19. #19
    CTB
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    Bad mechanic, we think alike. A friend of mine is looking into a time-sert design that he thinks will work. I knew all along the 6061 would fail, I just hoped it would have taken longer to do so. Hopefully I'll have a time-sert "fixed" aluminum piece and a new 6Al-4V titanium piece to play with in the next couple weeks. My design is definitely "shady," I know. Not much real estate in there to do what I want, but I hope I can make it work.

  20. #20
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    Quote Originally Posted by Jerk_Chicken
    I'm thinking it's going to keep doing this due to the side loading of the shock. It really needs a through bolt, which is not possible in this case.
    The biggest problem is that it is an M6 bolt that requires about double the engagement length that I have. You know, like the setup that Schwinn actually sold the bike with.

  21. #21
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    Still have that CAD file? Maybe constructing out of higher grade aluminum would fair better?

  22. #22
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    Keep looking, Sandwich, and you'll find this, which I think you'll enjoy.

    The birth of a titanium part - 4-Banger content

  23. #23
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    That is indeed awesome, and I found it after I posted above, but I take it you aren't making any more of those....16hrs of labor plus 200g or so of titanium isn't cheap...unless you love helping random homegroaners on the intertoobz. You ever do or think of steel? Weight would be heavier but an air shock with steel "trunion" would likely be similar to coil shock.

    Nice work on the ti, BTW.

  24. #24
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    Thanks. The 4-Banger frame is a porker already, so I never looked at steel. I'm not a material properties guy, but I'm assuming some form of stainless would work best for corrosion protection. The 6Al-4V ELI Ti we used has the strength of steel and is only slightly heavier than 6061. Very labor-intensive, though.

  25. #25
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    material properties = metallurgist.

    Since the Ti is so tough, how much wear did it create on your carbide cutters?

    When I was designing custom paintball parts, most of the parts were 6061, a few of the other companies ran Ti, but since the cutters would dull faster, material was more expensive, even for low grade Ti, the price increased. Best bang for the buck was 6061.

    Hardwarz

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