Newbie brakes

Discussion in 'UK and Europe' started by Paul, Mar 26, 2003.

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  1. Paul

    Paul Guest

    Hi, I guess that this is a pretty basic question, but I'm a novice and only just starting to get
    informed around doing my own maintainence.

    My bike has just had a service to check that everything is ok for the summer. The front brake blocks
    were worn and so were replaced.

    There is an occassional scuffing of a brake block against the rim of the front wheel. The wheel is
    aligned and the problem seems to be more about one of the brake callipers not fully returning to
    position after the brakes are applied. This was a problem that occassionally occured with the old
    blocks so I don't think that the change of blocks is a cause.

    I've tried tightening the adjustment screw on the calliper to move it away from the rim a bit, my
    main question really (showing my lack of confidence I guess) is to ask whether I can cause any harm
    experimenting with the adjustment screws.

    Thanks in advance to any experts out there who can help.

    Kind Regards, Paul
     
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  2. Alex Graham

    Alex Graham Guest

    Paul wrote:
    > my main question really (showing my lack of confidence I guess) is to ask whether I can cause any
    > harm experimenting with the adjustment screws.

    No.

    :)

    The return springs in cantilevers (I'm assuming these are what you have, or V-brakes) get knackered
    eventually, especially the front as thats probably the one you use the most.

    Do the brake arms have a wire connecting them whichs hangs off the main cable going to the brake
    levers? If you do, then you have normal cantilevers and the centering can be adjusted by simply
    sliding the yoke (bit connecting the two wires) along the transverse cable (the cable going between
    the brake arms)

    If you have brakes that have long, straight arms that seem to be operated by a single cable which
    goes across the top then you have V-brakes (shimano trademark). These are direct pull cantis (no
    transverse cable) brakes so the only centering control you have is the small screws at the bosses.
    You probably cannot move the brake pads relative to the brake arms, just up and down if you have
    these brakes.

    One possibility is that the brakes have not been loosened since the installation of new pads, so
    you may have to loosen the cable to accomodate the unworn pads. Theres probably an adjuster for
    this at the ends of the levers. Just adjust it so they are loose enough not to rub but tight enough
    for a quick response, and so the levers doesnt bottom out against the bar before the brake is
    properly applied.

    Sorry Ive rambled a fair bit there! Hope you understand what I'm on about :)

    Cheers,

    --

    -Alex

    ----------------------------------
    [email protected]

    http://alexpg.ath.cx:3353/cycling.php http://www.westerleycycling.org.uk
    ----------------------------------
     
  3. Paul

    Paul Guest

    Hi Alex and thanks for taking the time to reply.

    They are V brakes (cantilever might not be the right term for V brake arms, I guessed). The bike is
    fairly cheap and the brakes themselves are Tekro V brakes (run from Shimano Acera combined
    lever/shifter pods).

    I guess that I just need to check the centering. My main concern, being fairly inept at
    maintainance, was fiddling with the brakes which, after all, are fairly important.

    I am also a little unsure as to the optimum distance of block to rim (if there is one), the rear
    brake seems to engage rather more firmly than the front for the same amount of lever pull (this has
    always been the case from day one) and the blocks seem closer to the rim than on the front.

    Thanks again for you reply, Kind Regards, Paul.
     
  4. Alex Graham

    Alex Graham Guest

    Paul wrote:

    > I am also a little unsure as to the optimum distance of block to rim (if there is one), the rear
    > brake seems to engage rather more firmly than the front for the same amount of lever pull (this
    > has always been the case from day one) and the blocks seem closer to the rim than on the front.

    You probably have an cable adjuster where the brake cable leaves the levers. If not then loosen the
    allen bolt on whichever brake arm has the bolt holding the cable in place and pull it a bit tighter
    if you want to move the pads nearer to the rim.

    If your wheels are out of true (when you spin the wheel the rim moves from side to side) then you
    cant avoid setting the brakes further from the rim if you want to avoid rubbing.

    --

    -Alex

    ----------------------------------
    [email protected]

    http://alexpg.ath.cx:3353/cycling.php http://www.westerleycycling.org.uk
    ----------------------------------
     
  5. "Paul" <[email protected]> wrote in message
    news:[email protected]...

    > I am also a little unsure as to the optimum distance of block to rim....

    On my old bike I tended to adjust the blocks with about 3mm clearance, but my new bike has been set
    by the bike shop with almost no visible clearance at all! I was convinced that this would cause the
    blocks to rub the rims, but lifting the bike and spinning the wheels seems to show that there must
    be no contact as the wheel would presumably stop spinning pretty soon if there was any contact. No
    doubt with time the rims might loose some trueness requiring me to open the clearance a bit.
     
  6. Paul

    Paul Guest

    Hi,

    The wheels should be true as they were both checked and tweaked during the service. As far as the
    brakes go I've probably done my usual of tweaking things to get them 'just right' and messing up!

    I'll have another go and see how things shape up, I can always take it back to the shop again
    (they're pretty used to me turning up after mucking something up!)

    Thanks again for the input.

    Kind Regards, Paul.
     
  7. Call Me Bob

    Call Me Bob Guest

    On Wed, 26 Mar 2003 23:11:50 -0000, "Paul" <[email protected]> wrote:

    >The wheels should be true as they were both checked and tweaked during the service. As far as the
    >brakes go I've probably done my usual of tweaking things to get them 'just right' and messing up!
    >
    >I'll have another go and see how things shape up, I can always take it back to the shop again
    >(they're pretty used to me turning up after mucking something up!)

    The Park Tools site has an excellent collection of pages on bike maintenance here:

    http://www.parktool.com/repair_help/FAQindex.shtml

    Instructions for adjusting your V brakes are here:

    http://www.parktool.com/repair_help/howfix_linearbrakes.shtml

    Good luck! Keep practicing and soon you'll not need the bike shops help with any of your
    maintenance.

    Bob
    --
    Mail address is spam trapped To reply by email remove the beverage
     
  8. Pete Biggs

    Pete Biggs Guest

    Adrian Boliston wrote:
    > "Paul" <[email protected]> wrote:
    >
    >> I am also a little unsure as to the optimum distance of block to rim....

    Set by whatever feels best at the levers to use. Some people like blocks closer than others. But do
    always make sure the levers can't run out of travel (don't hit the bars when squeezed as hard as
    possible).

    > On my old bike I tended to adjust the blocks with about 3mm clearance, but my new bike has been
    > set by the bike shop with almost no visible clearance at all! I was convinced that this would
    > cause the blocks to rub the rims, but lifting the bike and spinning the wheels seems to show that
    > there must be no contact as the wheel would presumably stop spinning pretty soon if there was any
    > contact.

    (or would hear noise)

    Wheel and cable flex/stretch may cause the brakes to rub while riding so allow just a little bit
    more for that - particularly for the rear.

    ~PB
     
  9. Dave Kahn

    Dave Kahn Guest

    "Paul" <[email protected]> wrote in message
    news:<[email protected]>...

    > I am also a little unsure as to the optimum distance of block to rim (if there is one), the rear
    > brake seems to engage rather more firmly than the front for the same amount of lever pull (this
    > has always been the case from day one) and the blocks seem closer to the rim than on the front.

    Some people like to set the blocks as close to the rim as they can. It looks the business but IMO is
    not that critical provided you satisfy two key requirements. Firstly when the brake is fully applied
    there has to be a safety margin of unused travel left in the brake lever; on no account must it be
    stopped by the handlebar. Secondly when you let go again the rim should not touch the blocks at any
    point as the wheel revolves. The rim should also be centred within the gap between the blocks but a
    small error here is not critical.

    As the blocks wear the safety margin of unused lever travel will be reduced. You can restore it
    by turning an adjuster. This will either have a locknut you have to loosen to adjust and
    retighten afterwards, or it will have detents and a spring to stop it moving by itself. When
    there is no more movement left in the adjuster you either need new brake blocks or you need to
    pull more cable through.

    To do this you slacken the cable clamp bolt, turn the adjuster almost all the way back in, hold the
    brake blocks against the rim, pull more cable through and retighten the cable clamp making sure that
    the cable is properly seated and fully trapped by the clamp bolt. Then fine tune using the adjuster.

    You may have noticed that you need more than two hands for this job. You can either buy a special
    tool called, amazingly enough, a third hand, or you can free up one of your own by strapping or
    taping the brake shut while you're pulling and clamping the cable.

    --
    Dave...
     
  10. Al_mossah

    Al_mossah Guest

    You can check for trueness by removing the wheel and re-mounting it the other way. See if the
    rubbing occurs on the same side as currently. If it does, your wheel is probably fine.

    Peter
     
  11. Paul

    Paul Guest

    Thanks to everyone for the thoughts, I did the sensible thing and had it sorted at the shop, it was
    just a case of tweaking the adjusting screws to centre up the blocks and the guy did it for free.

    Thanks again, Paul
     
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