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  1. #1
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    Is it possible to route v-brake cable under bb?

    Dumb question, but I'll ask anyway;


    I'm building up this frame with v-brakes:




    Unfortunately there are no cable guides on the top tube to run the cable for the rear. I tried some stick on cable guides, but the combination of the weld and anodised finish means they didn't stick.

    I don't really like the idea of cable ties on the top tube (although I may have no choice).

    Does anyone know of a reason not to try touting the cable under the bottom bracket? Obviously there is the movement of the suspension, a lack of guides on the 'seat tube' and the sharp bend for the cable to take under the bb as issues to consider.



    Is this a stupid idea? Or should I give it a try? Any other cable routing suggestions welcome.

  2. #2
    251
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    These guys may have some ideas:
    Specialized FSR MAX backbone
    Dave
    Blog / Strava

  3. #3
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    If it were me I'd be worried about rock damage to the brake cable. Maybe I'm wrong but just seems like a bad idea to run on the downtube.

  4. #4
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    Quote Originally Posted by 251
    These guys may have some ideas:
    Specialized FSR MAX backbone
    Thanks, though those bikes have cable guides on the top tube, and I'm hoping this more generic forum might catch the attention of a wider audience than just specialized people. It looks like it should work in theory, but because I've never seen it done I'm wondering if there's something obvious I'm missing.

  5. #5
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    Quote Originally Posted by Tim-H
    If it were me I'd be worried about rock damage to the brake cable. Maybe I'm wrong but just seems like a bad idea to run on the downtube.

    I though the same thing Tim, but that's just how specialized do things:


    And I'm only talking about the v-brake cable, most of these bikes run hydraulic lines down there!

  6. #6
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    ...v-brake cable routing...

    Back a few years ago(probably before you were born) Raleigh,Schwinn,Motobecane etc., used cable clamps with integral cable stops. Check with some of your older neighbors, the local thrift shop, or even a recycling facility for one of the bikes from that era. You should be able to adapt those cable stops to your frame...big and tall

  7. #7
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    Having all those bends in the cable may make the brake's action pretty sluggish. But if you don't want to zip tie the housing to the top tube, it's pretty much the only option you have.

    Edit: you'll still have to zip tie the housing to the seat-tube area, so the cable is not flopping around all over the place. And you need downtube housing inserts to hold your housing snug. Probably a lot easier (with a lot better performance) to just run full-length housing and use a couple of zip ties to keep it tight to the top tube. Put some of those frame patches down first to prevent scuffing of the paintjob!

    Really weird that Specialized would make a frame with canti stops on the rear triangle but no housing stops on the frame...

  8. #8
    Hi.
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    Quote Originally Posted by big and tall
    Back a few years ago(probably before you were born) Raleigh,Schwinn,Motobecane etc., used cable clamps with integral cable stops. Check with some of your older neighbors, the local thrift shop, or even a recycling facility for one of the bikes from that era. You should be able to adapt those cable stops to your frame...big and tall
    That would require using something like a zip tie to hold them to the top tube, with no significant benefit over using full-length housing and just the zip tie (no stops.)

  9. #9
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    I have an old pre-vbrake Gary Fisher HT frame and to install the rear vbrakes, I just housing back to the rear v-brake, zip tied it to the frame and it has always worked fine.

  10. #10
    rebmem rbtm
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    That's strange, the frame looks like it wasn't sold with V-Brake mounts on it.

    http://www.specialized.com/us/en/bc/SBCBkModel.jsp?arc=2007&spid=22219&menuItemId=0

  11. #11
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    Solid housing the entire way IMO. Straight under the downtube, make it come up ABOVE the BB (which would be behind the crankset) and around to the front of the seattube area. Then, just a large loop from there through the hole in the frame the shock uses to the noodle for the brakes.

    This would eliminate enough of the tight turns and allow for suspension travel to be absorbed by the large loop. Not 100% sure it would work, as I haven't seen the extent of how the suspension moves, but it seems logical.

  12. #12
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    Thanks for all the replies guys:

    Cobba, to look at the Specialized website, it doesn't appear that any of the models shipped built up with v-brakes, but a couple of the models state that they are "disc compatible" where most say "disc only". I can't find a picture anywhere showing one of these bikes built up with v's. But the bosses are there, so someone must have considered this scenario.

    Big and Tall, I can't visualise the cable clamps/stops you're referring to. Maybe if you link to a pic? Which era are you referring to?

    Ettore and jtmartino, I had a little play with it this evening and mocked up two options:



    Under the bb but outside the rocker would work but probably likely to catch on my shoe as it's right by the cranks. Threading it through the rocker just seems like a bad idea.




    Tied to the top tube is obviously much simpler, but the way the tube tapers seems to me like the cable tie or pipecleaner would slide down and the cable start flopping about.

    So neither option seems ideal. But I can probably discount under the bb now.

  13. #13
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    Did you try the way I mentioned ? I don't mean to thread thru the rocker ... see attached crappy paint mock. I did a bad job drawing how curved the housing should be, but with the crank on there, the cable can probably make that corner near the BB with a really wide radius. There will be no housing-rub on your frame in the lower sections, because that part won't move. Then the cable will go straight into the brake and suspension movement will not change that angle (cable rub will happen inside the frame gap, however, but I think it'd work). The ONLY spot you'd need to add something would be at the FD-post zone, where you could use a simple ziptie likely . If there is not enough room on the chainring side, you could use the other side as well and I can almost guarantee you'll never hit it with your foot (regularly, anyways).
    Attached Thumbnails Attached Thumbnails Is it possible to route v-brake cable under bb?-snc12201.jpg  


  14. #14
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    Thanks ettore,

    I did try that, but I'm a bit short on cable and housing so the mockup didn't reach as easily that way. The way I've pictured it the noodle would fit into the brake nicely, but your way it didn't quite reach. I could have disconnected at the shifter I guess, but I didn't think of that when I was doing it.

    I'm getting some longer cables which will make it easier to experiment.

  15. #15
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    i dont know if id want to lose a brake line from a rock hit, so what about running the cable like ettore shows, around the rocker, but instead of go underneath the top tube... so your cable runs down the length of the top tube and almost straight into the brake...
    you could use housing to go around the side of the headset tube and maybe a zip tie around the headset and inbetween the top and down tubes...

    Its been a while since i had vee's but more direct wire = better braking right?

    and if i can ask, why not discs? even mehcs?
    2008 Kona Caldera

    "Today I saw my own son use a bicycle as a weapon....
    I seriously thought he was going to rape me"

  16. #16
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    K1lluaA, what you describe sounds like the pic in my earlier post where I've tied the housing on with the pink pipecleaner. Or have I misunderstood?

    Being the idiot I am, I ordered insufficient housing to do the job. I guess v brakes aren't normally routed such a long distance. I should have measured more carefully...

    I didn't take a photo, but the best way that would work in theory is under the bb, bending back in and through the shock mount on the top tube. Looked a bit silly though, and would interfere with the bottle cage location as the cable forms a loop through the middle of the top, down and seat tubes.

    The housing is quite stiff so you have make shallow bends, which is what makes the method drawn by Ettore difficult. I think I'm going to shelve the idea for now, and keep it tied to the top tube.

    Why not discs? Well I don't have the wheels or the brakes so it would be a costly exercise. I bought the frame specifically because it had v-bosses so I could use all the bits from my old bike.

    I do want to go to discs, but I'd like to do it properly, and I don't know much about the different options. i.e. should I get regular qr hubs, or are through axles a better idea? At some stage I'd like a lighter fork, maybe a TALAS, so I don't know if I'll limit myself if I buy a qr wheelset to suit the current fork. Then there's 6bolt vs centre lock, hydraulic vs mechanical...

    Basically I don't know enough about my options yet.
    Last edited by Tubbsy; 09-16-2010 at 10:25 PM.

  17. #17
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    i hope that loads, that is what i was talking about, i dunno if possible, but you would save some housing length and seems to me it'd be a bit safer...i hope that helps.

    blue line is my idea, sorry it didnt load yesterday...

    believe me, i understand the need to use what you have and save cash...
    Last edited by k1lluaA; 09-18-2010 at 12:48 AM.
    2008 Kona Caldera

    "Today I saw my own son use a bicycle as a weapon....
    I seriously thought he was going to rape me"

  18. #18
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    Hi,

    maybe you could try to mount a cable hanger together with the upper screw of the rear shock?

    I found this at http://www.nashbar.com/bikes//Produc...2_174820_-1___

    Don't worry, they are also available in black

    For the front you could attach a hose clamp to the downtube with a similar cable stop. For me this would be the best and shortest way for the cable. Not very elegant but worth a try.



    Rob
    Last edited by oz1um; 09-17-2010 at 10:47 AM.

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