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  1. #1
    pile rider
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    Q's: replacing v brakes with disc

    i have a 2001 rockhopper comp and need a new wheelset. i was looking around and found a great wheelset for cheap, but is disc only. i also found some avid BB5 disc brakes for cheap that could replace my v brakes since i'm getting new wheels anyway. would i need anything else besides the rotor, caliper, and mounting hardware if i get the disc only wheels? would i have to upgrade anything else on my bike before getting disc brakes? could the cable used for my v brakes be used for the disc brakes also?

    sorry about the newbie questions, but i can't find an answer to these specifically. thanks in advance!

  2. #2
    On MTBR hiatus :(
    Reputation: Speedub.Nate's Avatar
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    Assuming you have disc tabs on your frame and fork (being a 2001 Specialized, I have no doubt you're OK in that department), that's all you need.

    One tip: I know the BB5s are a great price, but spring for the BB7s. BB5s lack an important pad adjustment feature, and use a non-standard pad.

    On the cable, if you really want to be cheap, you can re-use your rear cable for the front disc. Your existing front cable will be too short for anything, and the rear will be too short for a rear disc.

    But don't be a cheap-ass, since you're going to have to cut the cable and housing down to fit the new installation. Spring for some new stuff. It's only a couple more bucks.
    Last edited by Speedub.Nate; 06-07-2007 at 01:19 AM.
    speedub.nate
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  3. #3
    local trails rider
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    If your frame and fork have attachmets for disk brakes, you will be OK.
    Check that the hubs are compatible with the rotors. Shimano has their own system for rotor mounting.
    The V brake cables are too short.
    I thought BB5 comes with cables but I am not quite sure.

  4. #4
    dru
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    I'd even spring for hydros. I've got shimano br555s and I love them. I have seen them brand new for 125 bucks on ebay. They are a great brake.

    Drew

  5. #5
    meh... whatever
    Reputation: monogod's Avatar
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    Quote Originally Posted by dru
    I'd even spring for hydros. I've got shimano br555s and I love them. I have seen them brand new for 125 bucks on ebay. They are a great brake.

    Drew
    if you get cable disc brakes, get bb7's. PERIOD. dont screw around with anything else. they are simply the best cable disc, and quite frankly better than some hydros.

    i agree that the 55's are a great entry level disc system and they're really easy to adjust. (if i recall they dont use shims... i HATE shims!)

    or pony up a few more bucks and get a nice used set of juicy 5 or 7's. either will offer vastly increased feel and performance over the 555's for just a little more cabbage.

    used set of juicy 7's: http://cgi.ebay.com/AVID-JUICY-SEVEN...QQcmdZViewItem

    brand new set of juicy 5's: http://cgi.ebay.com/AVID-JUICY-5-HYD...QQcmdZViewItem

    brand new bb7's: http://cgi.ebay.com/New-Avid-BB7-Bal...QQcmdZViewItem
    "Knowledge is good." ~ Emil Faber

  6. #6
    dru
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    shims

    the 555s use shims which put me off at first too. I have found that they are only used for ballpark alignment, the pistons do the rest. You can run them way inside or out, shim wise, and the return springs and pistons compensate with the correct clearance on both sides of the disc. A buyer needs to be aware that there is a separate front caliper for post mount and for ISO.

    Drew

  7. #7
    meh... whatever
    Reputation: monogod's Avatar
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    i stand corrected on them being shimless. shoulda known better since shimano makes most of their brakes (even xt/xtr) with shims.

    shims are used for more than ballpark alignment. if proper parallel caliper/pad alignment is not achieved the pads will rub and improperly engage. this causes accelerated wear and increased fluid temp, which then reduces braking feel and response.

    yes this can be corrected and compensated for to a certain extent by dialing the pad distance out, but that simply increases lever response time and decreases actuation point and feel. these adjustments should be used to fine tune rather than make the initial alignment. these adjustments also have no affect on the parallel adjustment.

    proper alignment is even more crucial with single piston brakes such as the 555 since only one pad is actually moving to make contact with the rotor. one pad must float a minute distance away from the rotor while the piston on the other side causes the pad on that side to move thus clamping the rotor between them. the less slop and more preciseness at the lever one desires, the more critical initial proper alignment becomes.

    on floating mount (non shim) systems initial alignment is easy, just loosen the caliper mounting bolts, grip the lever, and tighten down the bolts. then fine tune the pad float.

    its not that shimmed systems suck, i just dislike having to take the time to set them up when a much better method is used by the majority of other brakes on the market.

    i guess shimano always has to be different...
    "Knowledge is good." ~ Emil Faber

  8. #8
    dru
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    single piston?

    Sorry, I don't think you're entirely familiar with the 555. It has a dual piston caliper, with one on each side of the disc. That is why the amount of shims used is not super critical. One piston simply protrudes more than the other if the shims are incorrectly set.

    Drew

  9. #9
    meh... whatever
    Reputation: monogod's Avatar
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    Quote Originally Posted by dru
    Sorry, I don't think you're entirely familiar with the 555. It has a dual piston caliper, with one on each side of the disc. That is why the amount of shims used is not super critical. One piston simply protrudes more than the other if the shims are incorrectly set.

    Drew
    went to the parts bin in the shed and yep, youre right, theyre dual.

    this lessens the importance of pad/rotor spacing a tad over a single piston caliper, but the caliper/rotor parallel alignment is still just as critical and for the same reasons cited.
    "Knowledge is good." ~ Emil Faber

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