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  1. #1
    Cycles With Children aloKen's Avatar
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    Disc Brake Fork upgrade to Rigid MTB

    Ok, I've got a early 90s rigid steel MTB that I would love to put a front disc brake on. I think I would just need a new fork with disc tabs, and some BB7s.

    So all the forks I can find are "suspension-corrected". Where are the non-suspension-corrected MTB forks with disc tabs? Am I correct in assuming that a suspension-corrected fork would mess up the geometry on my never-been-suspended MTB?

    Any ideas?
    The more I tinker with bikes, the better I understand why it was bicycle mechanics who invented the airplane.

  2. #2
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    Measure your current axle to crown distance and look for something similar.

  3. #3
    Senior Member
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    Also look at cyclocross forks. Despite the fact the the UCI previously banned disc brakes many manufacturers included disc brake mounts.

  4. #4
    coprolite fietsbob's Avatar
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    thing is suspension forks 1st had rim brakes, then disc brakes came on,
    so the 2 are off timeline for an off the shelf short blade MTB fork

    I think it requires a fabrication project and you really need lawyers lips fork tip if the caliper is on the left

    have the ISO tab put in front on the right and that's better.

    spend in country at your local framebuilder.

  5. #5
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    Quote Originally Posted by aloKen View Post
    Ok, I've got a early 90s rigid steel MTB that I would love to put a front disc brake on. I think I would just need a new fork with disc tabs, and some BB7s.
    Pretty much so. Just make sure you get the version that matches the pull of your brake levers.

    Quote Originally Posted by aloKen View Post
    So all the forks I can find are "suspension-corrected". Where are the non-suspension-corrected MTB forks with disc tabs?
    As Fietsbob says, first sus forks began to replace rigids, then discs began to replace rim brakes. It's a bit like trying to find a flatscreen computer that can read floppys.

    Quote Originally Posted by aloKen View Post
    Am I correct in assuming that a suspension-corrected fork would mess up the geometry on my never-been-suspended MTB?
    It's more a question of changing the geometry rather than messing it up. Rideability is not at risk.
    IME they do just fine structurally too, although the head tube will see some more stress.

    Quote Originally Posted by aloKen View Post
    Any ideas?
    Pertty much as already posted.
    Look for the disc brake fork with the shortest axle-to-crown you can find, slap it on and see how it handles. Have disc brake tabs added to your current fork(assuming it's steel) or have a custom fork built for you.

  6. #6
    Cycles With Children aloKen's Avatar
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    Thanks everyone for the ideas. I've looked at 'cross forks, but they're all 700c, so the geometry would also change. This bike is a 26". I'll measure my axle to crown and see what I can find.

    I'm afraid this is a bit like looking for an LCD with a floppy drive. I suppose I could just replace the bike with a rigid 29er, but this seems like such a simple upgrade I hate to replace a perfectly good bike.
    The more I tinker with bikes, the better I understand why it was bicycle mechanics who invented the airplane.

  7. #7
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    Hunt around at LBS's in your area, you never know what may turn up, but it is likely that such a product was never produced. My rough weather commuter is an early suspended MTB (1994) with a rareish headset, a YST roller bearing 1-1/8" threaded which I love and I also love my Ritchey quill stem and Scott AT-3LF bars. I wanted to keep the cantis but change out my RockShox Quadra 10 fork for a suspension corrected(for a paltry 43mm travel) *threaded* 1-1/8" rigid. I figured they just didn't exist, but the first shop I asked at was able to dig out of mothballs a NOS Kona Project 2 with the correct steerer length. It completely transformed the bike, it is so much faster and I can ride it no hands as it tracks so straight. I feel like I got a new bike for $20.

  8. #8
    Pro Paper Plane Pilot wunderkind's Avatar
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    Disc brake rigid forks is available. Just look around. I got one a few months ago to replace my squishy front. Wanted to keep my disc set-up. Patience is key. It was a DMR Trailblade II piece. Boy was it overbuilt.
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  9. #9
    another retro grouch Mr IGH's Avatar
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    Dimension makes 'em for non-suspension bikes, 410mm axle to crown, you can order one and have it next week:
    http://www.universalcycles.com/shopp...3&category=703

  10. #10
    coprolite fietsbob's Avatar
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    The data that counts is axle to fork crown seat, rather than tire size..
    people have swapped disc brake
    26 fat tire wheels and 28'' skinny tire in the same MTB fork before.

    So Crown width .. and so tire width capacity , is a second consideration,
    compare by another measurement.

  11. #11
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    The geometry is going to change as well as the braking power between disc and rim brakes will be different. Unless you already have the parts it would be best to get a new bike and swap your XT parts to that bike, you need a Surly fork or similar $120, brake $60- $100,wheel $100. Specialized has a Hardrock disc for about $450 new and then swap your better parts to that bike and then sell or keep the old bike when rebuilt with the new parts. Also before you invest make sure the rest of the bike is in perfect order so this doesn't cost you several 100 more to complete the project. I hated having one disc and one cantilever brake. Good luck

  12. #12
    Member miSSionary's Avatar
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    To the OP, keep in mind that if you change the fork for disk you will also need a new hub/wheel as the hub will need holes to attach the disk.
    Try to find a Bianchi fork, those are not corrected, they are heavy.
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  13. #13
    Cycles With Children aloKen's Avatar
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    Ok, now we're getting somewhere. I measured my axle-crown distance, it's 390 mm, so that Dimension fork that's 410 shouldn't change the geometry hardly at all I would think.

    Thanks for the link IGH. (BTW, I just put a Nexus-8 on my wife's mixte, she LOVES it!)
    The more I tinker with bikes, the better I understand why it was bicycle mechanics who invented the airplane.

  14. #14
    another retro grouch Mr IGH's Avatar
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    Quote Originally Posted by aloKen View Post
    Ok, now we're getting somewhere. I measured my axle-crown distance, it's 390 mm, so that Dimension fork that's 410 shouldn't change the geometry hardly at all I would think.
    I agree, FWIW It lowers the head tube angle slightly, that's better than having the HA slightly steeper, IMHO.

    Thanks for the link IGH....
    I bought the 700C version of this fork for my commuter (as have a few others on BF). I like my exisiting C&V frame, I just wanted a disc fork, it was worth it to me. A new bike doesn't interest me.

  15. #15
    coprolite fietsbob's Avatar
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    Dimension is a QBP brand, so your local can get them
    [ option of sales tax versus shipping in most states]

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