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Help needed from bicycle experts

  • 08-10-2010 12:55pm
    #1
    decoratinghouse
    Registered Users Posts: 48 ✭


    My son's bike has had problems with the back brake. I'm looking for advice as to whether it is repairable.

    When the brake is pulled, the piece that grabs the wheel doesn't squeeze tight enough to stop the wheel.

    I took it to a bike repair shop. There was also a problem with the saddle so I left it in to be repaired. It didn't work so I brought it back. The guy couldn't figure out what do do with it except charge me more money to change the brake pads. and as this was unlikely to work I left the shop with the bike.

    Any suggestions?


Comments

  • #2
    victorcarrera
    Registered Users, Registered Users 2 Posts: 1,059 ✭✭✭victorcarrera


    IMO the back brake on a bike is of little or no use as your weight is over the front wheel when you brake. Even a light squeeze on the back brake locks up the back wheel.
    It is unusual the bike shop couldnt fix it though.
    However, clean the wheel rim of any oil or mud.
    The quality of brake pad/block is very important.
    Check and oil all moving parts and ensure the cable is not loose, frayed or worn causing it to stretch.
    If the brake lever comes close to the handlebar when actuated the cable is probably too loose. There is usually and adjustment thumb screw at the brake lever or at the brake caliper to tighten it up.


  • #3
    seamus
    Registered Users, Registered Users 2 Posts: 68,317 ✭✭✭✭seamus


    Take a few minutes to examine the brake, pull on the lever and see how it works.

    It would be impossible to say what kind of brakes the child's bike has at the moment. Have a look here: http://en.wikipedia.org/wiki/Bicycle_brake_systems

    If it's a full-size or junior size mountain bike, he very likely has V-Brakes or Cantilevers.

    If it's a bike for a very young child, it's probably just a cheap caliper brake.

    In all cases, they operate on the same principle: The brake is attached to the brake lever by a wire cable. When you pull on the lever, this pulls in cable, and the brake then pulls the two brake pads together.

    Very simply, the brake pads should both grip the rim (the steel part of the wheel - not the tyre!) at the same time and when the brake lever is pulled somewhere between 25% and 75% of it's maximum.

    Don't expect the back brake to stop the bike when it's moving. When the bike is moving, pulling on the back brake should slow it, and really jamming on the back brake should cause the wheel to lock and skid.


  • #4
    decoratinghouse
    Registered Users Posts: 48 ✭decoratinghouse


    seamus wrote: »
    In all cases, they operate on the same principle: The brake is attached to the brake lever by a wire cable. When you pull on the lever, this pulls in cable, and the brake then pulls the two brake pads together.

    Very simply, the brake pads should both grip the rim (the steel part of the wheel - not the tyre!) at the same time and when the brake lever is pulled somewhere between 25% and 75% of it's maximum.

    Don't expect the back brake to stop the bike when it's moving. When the bike is moving, pulling on the back brake should slow it, and really jamming on the back brake should cause the wheel to lock and skid.

    When the brake lever is pulled 100% it doesn't do anything to slow the wheel.

    The guy in the shop said it should be fine as you really only need the front brake. It's years since I have ridden a bike but I remember pulling both levers. Wouldn't you go over the handlebars if you only had front brakes?

    I told him I couldn't let a 10 year old boy out on a bike with only front brakes.


  • #5
    petethedrummer
    Registered Users, Registered Users 2 Posts: 7,604 ✭✭✭petethedrummer


    decoratinghouse wrote: »
    I told him I couldn't let a 10 year old boy out on a bike with only front brakes.

    I'm surprised a fella in a bike shop can't fix brakes. Unless its an ultra cheap bike (or BSO) and the components are not be easily fixable.

    Try another bike shop.


  • #6
    BostonB
    Closed Accounts Posts: 18,056 ✭✭✭✭BostonB


    Go to a decent bike shop. That one you went to is rubbish,


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  • #7
    -Chris-
    Closed Accounts Posts: 12,035 ✭✭✭✭-Chris-


    Can you take a pic of the brakes and post them here?


  • #8
    fishfoodie
    Registered Users Posts: 564 ✭✭✭fishfoodie


    -Chris- wrote: »
    Can you take a pic of the brakes and post them here?

    Good plan Chris.

    It could be a multitude of things, but you'll probably be able to tackle most of them yourself if you've a few basic tools, & if your 10 YO is interested they could probably do it themselves, or at least help ;)

    One possibility is that the brake cable is ancient & corroded & the force required to overcome just this friction, means you get zero force from the pad to the rim when you brake. Its a doddle to fix with just a new brake cable & a little tweaking.


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