looking for framebuilders willing to do some mods- Mtbr.com
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  1. #1
    since 4/10/2009
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    looking for framebuilders willing to do some mods

    I have a 1980's Trek 420 (4130 True Temper cromo) I want to turn into a belt drive disc brake commuter. Meaning I need new rear drops installed. I'd like to also use an Alfine 8spd IGH on this, which means the rear drops also need to be spread by 9mm (126mm-135mm) in the process.

    I'd also need a fork with disc tabs for this bike. I have the stock fork that came with the bike - could tabs be added to it (I'm sure the tabs could be added easily enough, but what I do not know is whether the fork could handle the stresses from the brake caliper), or would I need a new fork?

    I am talking to a builder now, but I'd like to get 2nd opinions on some of this stuff.

    Here's the drive-side dropout that I'm looking to replace:
    <a href="https://www.flickr.com/photos/[email protected]/6047419067/" title="Trek 420 project bike by mtbikernate, on Flickr"><img src="https://farm7.static.flickr.com/6061/6047419067_93ec5087bc.jpg" width="500" height="333" alt="Trek 420 project bike"></a>

    I got most of the parts off of the frame today, and I don't see tons of rust on the interior of the tubes in the bottom bracket and seat tube. I'm just not sure what the appropriate threshold for rust would be that would make the mods I want impossible for this frame.

  2. #2
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    Where are you located?

  3. #3
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    With belt drive you need to have very stiff chain stays or you will get a popping noise. I don't think that bike is going to handle it.

    Tim

  4. #4
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    This sounds like a cool project, but I think it might be financially in your interest to look at other frames. If you were doing the mods yourself for fun/learning/experience it would be one thing, but I don't see how a builder can do those mods and not price it similarly to some low-price new frames. I.e. Vassago Fisticuffs (these were on sale for <$250 previously) or other Taiwan steel frame (these are still great quality). Your Trek frame is prob worth $80-100 on CL anyways?

    Rim brakes and chain drive IGH would still work well, however, I think commuters benefit from discs similar to your initial inclination.

    Re: fork -- I think you'll need a new fork, the disc forces on the L leg will be too great and you will have tracking problems.
    Too many bikes, not enough time.

  5. #5
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    Forget it.

    The belt has requirements (chainstay stiffness, sprocket clearance, etc) that are going to necessitate basically rebuilding the rear end of the frame. Once that's all done and it's repainted, you'll end up having spent more than getting a new bike.

    -Walt

  6. #6
    since 4/10/2009
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    Quote Originally Posted by Walt View Post
    The belt has requirements (chainstay stiffness, sprocket clearance, etc) that are going to necessitate basically rebuilding the rear end of the frame. Once that's all done and it's repainted, you'll end up having spent more than getting a new bike.

    -Walt
    I've been reading about that. I'm talking to a builder about this stuff and he's willing to do the work. We haven't talked labor costs for all of it yet. Depending on the things that need doing and how much they'd cost, some plans might change but we'll see. I've got an e-mail off to Gates Corporation to find out if they can give me more details about the chainstay stiffness needs so I can talk to the builder about what he can do to get it up to spec.

  7. #7
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    Universal Transmissions GmbH

    PDF down on the right. Also check the Alfine clearance drawings also down on the right. The Alfine has a very narrow belt line and the belt will run right off the cog if the belt line is off even a tiny bit.

    Tim
    ps i have a belt drive /Alfine bike. Not a big fan of the combo for various reasons and will be switching to a Rohloff very soon.

  8. #8
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    Tim - will that be chain/Rohloff or belt/Rohloff? I saw your thread where you attempted to stiffen the stays on the Raleigh.
    Too many bikes, not enough time.

  9. #9
    since 4/10/2009
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    Quote Originally Posted by TimT View Post
    Universal Transmissions GmbH

    PDF down on the right. Also check the Alfine clearance drawings also down on the right. The Alfine has a very narrow belt line and the belt will run right off the cog if the belt line is off even a tiny bit.

    Tim
    ps i have a belt drive /Alfine bike. Not a big fan of the combo for various reasons and will be switching to a Rohloff very soon.
    Thanks for that link. Very helpful. I may have to be satisfied with only having disc tabs installed and going SS chain for this build, but I will make sure the builder I'm talking to has the described measuring device before making a final decision and shipping my frame off. Seeing the actual max deflections does make it look like this frame would require at minimum a good bit of reinforcement to get up to spec for belt drive.

    I don't live in a terribly hilly area so SS would work if it turns out in fact to be my best option.

    I would be interested to hear about how you became an un-fan of the Alfine/belt combo. I have done some reading about the gear ratios on the Alfine 8 having odd spacing. Does it have to do with that by chance?

  10. #10
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    Nate
    http://forums.mtbr.com/frame-buildin...ct-617192.html
    Link to my Alfine/29er/belt drive build.

    Linnaeus
    It will be a belt drive. I just ordered a pair of Blunt SL's to build the new wheels Monday.I should be able to mount them on the test bike and work out how I want the cables to route....If I can finish working on my stupid house I'll finish the new frame........sigh.

    Tim

  11. #11
    since 4/10/2009
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    Ok, Tim - that clears up your issues regarding Alfines and belts. I really don't want to have to go through what you did to get your chainline issues dealt with. I think I'll keep this a SS. Your work with the foam is interesting. Not sure about the trial and error process involved AFTER spending the money on the belt drive system, though.

    I will see what the framebuilder has to say about those documents you linked me to earlier (I sent him the frame flex link this evening).

    There are certainly some concerns here that need to be addressed. I do have to say, though, that I sorta wish I had taken at least one of the welding classes my high school offered. Framebuilding is a pretty cool process and something I might pursue later as an expensive hobby.

  12. #12
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    Nate
    Most local community colleges have night time "trades" classes. See if yours has a welding class. Take it. Most of the instructors I've met are very cool and let the students barrow the equipment (after class) for extra credit projects.


    Tim

  13. #13
    since 4/10/2009
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    Quote Originally Posted by TimT View Post
    Nate
    Most local community colleges have night time "trades" classes. See if yours has a welding class. Take it. Most of the instructors I've met are very cool and let the students barrow the equipment (after class) for extra credit projects.


    Tim
    That will have to wait for now. Not gonna happen when I'm trying to finish a master's thesis. ;-)

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