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  1. #1
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    Bolt Cog to ISO Disk Mount

    I am looking to give the fixed gear thing a good trial, after having a chance to take a spin on a fixie briefly in a parking lot (kinda liked the feeling). I saw on 63xc.com an article on converting a disk hub to fixed gear by bolting a cog to the disk mount and turning the wheel around. Are there any pitfalls with doing this (i.e. stresses on the mount, chainline, etc...). The bike is currently a singlespeed, so I believe the hub is already reasonably centered. Also, the bike has an EBB, so I do have a way of tensioning the chain, plus I could adjust the chainline a couple of mm either way at the BB.
    I would like to try fixed gear as inexpensively as possible.
    Thanks.

  2. #2
    Senior Member abeyance's Avatar
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    As far as doing this, you will be fine.

    I beleive either paul, boone ti, or white industries makes a cog for this exact purpose.

    Stresses on the disk mount from braking is far more than what you can put on the pedals, so don't worry there.

    As far as chainline is concerned, the mm that it is off by doesn't really matter, sure you lose a bit of efficiency, but the chainline is signicantly better than going 22/12 or 44/12 or something like that with standard mtb gearing.

    Like crack, try it once and you are hooked.
    not banned anymore

  3. #3
    LF for the accentdeprived
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    You gotta check if the chainline will work... dunno how disc rears are set up, but it's not hard to modify.
    Don't you worry about stresses. A disc rear hub with a fixed cog bolted on is the strongest cog setup ever made by a long way. Waaaay more bomproof than track hubs, cassettes or anything else.

    Here is a thread with my bolt-on-cog experiences. Boone makes a $$$ Ti cog and there's another option in that thread somewhere. Or drill/have a machinist drill your own. Cassette BMX cogs work.
    Quote Originally Posted by dutret
    Do you deny that you are clueless or do you just think that "moron" didn't need to be tacked on there?
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  4. #4
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    Thanks for the reassurance abeyance. I think the brief parking lot trial was enough to get me hooked, but I do want to give it an extended trial before commiting to either buying a bike, or spending lots'o money on a fixed gear wheel (hub). As the bike in question is a mtb (Gary Fisher Rig), this will give me a chance to not only try a fixie on the road, but possibly on some singletrack (nothing too technical). This will help me in possibly deciding what type of bike to build up as a fixie.

  5. #5
    Banned zelah's Avatar
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    do you ever find yourself looking a thread and not know why on earth you would click it? and not remember clicking it?

    how did i get here

  6. #6
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    Just a quick update. Over the weekend I attempted to drill out a cheap shimano BMX cog, and found the cog to be made of the hardest material known to man. Even using cobalt and masonry bits yielded nothing more than a slight mark on the cog.
    I posted for advice to a local forum catering to the singlespeed crowd, and one member has graciously offered to send me a drilled cog that he no longer had a need for. I'll post back with how my first true fixed gear ride goes.

  7. #7
    ya'll can't mush me vomitron's Avatar
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    I gave mine to a machine shop. I think he did it for $10 in about 2 minutes using a carbide bit. Supposedly, nothing else will work. This was an EAI cog, by the by (3/32).

    Oh, and for anyone considering doing this, I've had this setup for about 9 months now, with an average of roughly 500mi a week, with absolutely no problems (once I got my axle issues solved...should've used a shimano hub). The chainline was simple, and I made a zero dish dope wheel for under $60.
    Last edited by vomitron; 10-24-06 at 05:35 AM.

  8. #8
    LF for the accentdeprived
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    Tsk tsk. You didn't do your homework. I did say in my thread that the Sh DX cog is pretty ****ing hard hardened steel. Even kills a couple of carbide bits if you catch it in a bad mood.

    BTW, Vomitron: did you saw/file/grind off the lip or just turned it towards the hub?
    Quote Originally Posted by dutret
    Do you deny that you are clueless or do you just think that "moron" didn't need to be tacked on there?
    Bike on flickr and on FGG

  9. #9
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    I'd just like to update.

    I posted this question (actually about drilling f$#^%^ hardened cogs) to a local singlespeeders forum, and someone responded that he had a drilled cog he could send me. It turns out he did that to try the fxed gear thing, and liked it so much he bought a proper hub.
    It arrived last Tuesday, and I bolted it up, adjusted tension and chainline, and went for a ride around town. Dang, the thing was a hoot to ride . I was able to remember to pedal on my own without the bike reminding me. I was a bit choppy when slowing down by putting backpressure on the pedals. Total ride distance was about 5 miles, with a couple of small hills.
    On Wednesday, I took it to a local trail system that I ride on a weekly basis (Stony Creek in SE Michigan), for a little dirty play. Hopefully I don't get flamed too badly, but I did ride it on the singletrack. I started with a few miles of doubletrack/fireroads, and then rode a 1 mile stretch of singletrack which is quite flat and basically a beginner/intermediate ride. After that, I rode a few more miles of doubletrack and then on to the park's main singletrack, which has quite a few short climbs, and a very nice flow. I was quite impressed with how I was able to handle the trail on the fixed gear; it seemed quite natural to me. This was helped by the fact that I am very familiar with that trail. I liked the "direct feel" I had with the trail, especially on looser sections.
    I was running a front brake (this is my singlespeed mtb), but I only used it a couple of times on the faster downhill (doubletrack) stretches. My legs were sore for a couple of days afterwards, especially my quads. This was in spite of only doing 2 laps of the singletrack, when I usually do 3~4 laps.

    Druggies talk about getting another "fix". I think that term is quite fitting: I can feel myself getting hooked after just a couple of fixed gear rides.

  10. #10
    Yup pyze-guy's Avatar
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    Quote Originally Posted by bh357
    Just a quick update. Over the weekend I attempted to drill out a cheap shimano BMX cog, and found the cog to be made of the hardest material known to man. Even using cobalt and masonry bits yielded nothing more than a slight mark on the cog.
    Its made of tempered steel I believe and needs to be 'untempered'. Heat it really hot and dunk in cold water. Will drill no problem. Then retemper. Worked for me after discovong how easily cobalt bits were getting destroyed.
    When sadness fills my days
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