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  1. #1
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    New question here. Loss of braking power!

    Hi all,

    In case you'd rather not read the 'essay' (just the question) then I'll put that first:

    How can I get power out of my brakes again? Should I try a DISC brake cleaner from say Halfords, or do I need to get hold of some isopropyl alcohol - does this really do magic? For the detail if you can be bothered please read below...

    I have Giant MPH 3 hydraulic brakes (apparently a version of Hope C2's), I bought them second hand to upgrade the unbranded hydraulics on a Shogun Paranoid (a bike made by Falcon cycles - if that helps!) I specifically bought those brakes after having used them on a hired Giant XTC a while ago and being very impressed with the power.

    Anyway all was well... for a few weeks... then after a ride in the wet, I found I no longer had the power that the brakes used to give. I had to really squeeze the lever to stop quickly and was unable to lock the rear wheel at all! Previously if I wanted to I could quite easily lift the rear wheel with one finger on the front lever! Anyway I took out the pads and cleaned them with washing up liquid and bike cleaner (Muk Off) and also cleaned the rotor. After a while the rear seems to have regained some of it's power - but by no means all. The front however is still pretty bad. So after sanding the front pads, and still not seeing much improvement, I bought some new cheap pads. And yes... still no improvement although I should add I've only ridden about 5 miles on the new pads.

    OK I'm really sorry for going on so much, and I probably could have summed up my question in two lines, but I like to give detail...! SO MY QUESTION IS, (as above)
    WHAT SHOULD I DO NOW? Should I try a DISC brake cleaner from say Halfords, or do I need to get hold of some isopropyl alcohol - does this really do magic?

    Thanks ever so much in advance, if anyone is still reading.

  2. #2
    mmm
    Reputation: timehoc's Avatar
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    It sounds like you need to bleed your hydraulic lines. Over time, tiny air bubbles will get into the line weakening brake power.
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  3. #3
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    Thanks for the speedy response.

    Despite my limited knoledge of hydrulic systems, I doubt they need bleeding, when I bought them about a month ago I was told they had been bled two months ago, and from what I've read Giants MPH brakes generally go years before needing bleeding. The lever only moves a litte now with the new pads, doesn't it have lots of travel when it needs bleeding? Could be I'm completely wrong - just asking advice!

  4. #4
    Double-metric mtb man
    Reputation: Psycho Mike's Avatar
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    Isopropyl is a good investment....it is cheap and does a good job or getting stuff off rotors (and to a lesser degree pads). If you rode through a slick on a puddle, you may have contaminated the rotors and your pads. I'd start by cleaning the rotors really well with isopropyl and putting in a new set of pads.

    If that doesn't do it, I'm wondering if perhaps you also need to bleed the brakes...you mentioned about upgrading brake lines....if you've done that, perhaps some air got into the system. That would cause a spongy feeling in the lever and seriously kill off power.
    As if four times wasn't enough-> Psycho Mike's 2013 Ride to Conquer Cancer Page

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  5. #5
    mmm
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    Quote Originally Posted by modo
    I bought some new cheap pads. And yes... still no improvement although I should add I've only ridden about 5 miles on the new pads.
    Also, have you properly bedded in the new pads? Weak performance will be expected until they're properly bedded.
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  6. #6
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    Hi,

    what sort of distance would I need to go approximatley to bed in the pads? Is it not like a few miles with say 10 hard brakings? Or is it often much more than that?

    Thanks a lot.

  7. #7
    Are you talking to me?
    Reputation: damion's Avatar
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    Have you read this already?

    http://www.mtbr.com/techtalks/brakes/brakesfaq.shtml



    If so, try strapping the brake levers tight to the bars overnight using zip ties. Make them good, and tight, and let the bike stand overnight. YThis may force any small amount of air to the master cylkinder, where it can be compensated for.
    gfy

  8. #8
    Nightriding rules SuperModerator
    Reputation: crisillo's Avatar
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    I agree with Mike, the pads are probably contaminated... a good clean up and new pads might bring them back to life..

  9. #9
    ...idios...
    Reputation: SteveUK's Avatar
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    Try this for bedding in;

    Wipe rotors with Isopropyl Alcohol and dry thoroughly.

    New or old pads, use a sheet of sandpaper, around 100 grade, and rub the pad against it in a figure 8 pattern. Blow any dust away from the surface of the pad. Do this until th esurface of the pad is flat and 'clean'. If I can't clean a pad by sanding, it gets binned. I won't use any kind of cleaner.
    Refit the pads head outside with a bottle or pint glass of fresh, clean tap water. Get up a head of steam and brake hard. Pour water liberally over the caliper. Pedal off again, this time with the brake applied lightly. As you pedal you're going to feel the pads bedding in to the rotor. Keep going, pulling the brake gradually harder as you have to pedal harder. Do this for 20-30m and then pour water of the caliper again. Repeat a mix of hard stops, water; brake/pedal, water until your brakes are hpow you like them. I can get two Hope Minis bedded in in under 10mins using this method. They'll improve further after a little trail time, but at least you'll have decent braking to begin with.
    .
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  10. #10
    Meh.
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    Quote Originally Posted by damion
    http://www.mtbr.com/techtalks/brakes/brakesfaq.shtml



    If so, try strapping the brake levers tight to the bars overnight using zip ties. Make them good, and tight, and let the bike stand overnight. YThis may force any small amount of air to the master cylkinder, where it can be compensated for.
    Actually, I'm fairly certain that squeezing the lever isolates the MC from the rest of the system.

  11. #11
    Are you talking to me?
    Reputation: damion's Avatar
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    Is that dependant on the system?

    Quote Originally Posted by XSL_WiLL
    Actually, I'm fairly certain that squeezing the lever isolates the MC from the rest of the system.
    My method seems to work on Hayes and Magura models, but maybe I am just getting old.
    gfy

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