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  1. #1
    mtbr member
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    Hayes problem, need some help

    On my DH bike I have Hayes HFX-Mags and they work fine. Stock lines, 8" rotors, and GRC levers. I can bleed these and they just keep going strong.

    NOW on my other bike I have Hayes HFX-Mag's as well, but started noticing something odd. The rear brake line moves when I apply the brake. It moves like you can hold it and feel it move. I have bled the system more than once and seem to get air bubbles no matter what. I can't lock the rear up or anything if I try to. It gets close but just not there. There are new pads and a new rotor out back and the pads have been burnt in.

    Are hydro lines suspose to move like that when you apply the brakes? Should I try a new line and see if that fixes it? It is starting to drive me nuts. To the point where I've thought about just buying another rear brake OR finding a different set of brakes all together.

    Any ideas?

  2. #2
    newly converted MTBer
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    Are you noticing any performance loss since the hoses started moving? Ideally, of course, the idea is that the hoses transfer 100% of the energy from the lever to the brake, but this is never the case in reality. since fluids are incompressible, it will find the path of least resistance to go from high pressure to low, evening out the distribution of pressure. This usually means that the liquid will try to maintain the volume you have displaced at the lever in the master cylinder, by moving to some place (the pistons) where the volume can be made up for. Once all that volume is maxed out, and pressure is still applied, some energy is transferred evenly to the walls of the hose and other components in the system, causing it to want to straighten out in a last ditch effort to find more room.
    in other words, it's perfectly natural. If it bugs you that it wiggles around, you might try tethering it to your frame.
    Last edited by pcroxford; 06-20-2007 at 11:40 AM.

  3. #3
    mtbr member
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    So night 3 now, trying to bleed rear brake, non-successful.

    I pump fluid through the caliper, I watch for bubbles at the lever, when no more bubbles come out I close the caliper bleed hole, go make a mess and remove the hose that is in the lever. I leave it full of fluid so I can make sure everything is done as far as the bleed goes. Does that seem right? Should I not fill the lever up so much with fluid?

    I am still getting a funny lever feel on the rear brake. My other bike which also has HFX-Mag's feels fine.....my Dirt/4X type bike has the same HFX-Mag's on it and the front is butter, the rear sucks. I can't even lock the rear up or come close to it and the lever feels funny (nothing like my other bikes)

    Are there any tips/tricks/hints to bleeding rear brakes?

  4. #4
    mtbr member
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    It's easier if...

    you remove the caliper from the mount and hold it in your hand while you bleed. That way you can rotate it around to let gravity work the air back into the bottle or out through the master cylinder. I've done thousands of Hayes bleeds and removing the caliper always make the bleed better.

    You'll hear from several "Experts" in other brake threads that you only need to push fluid through and not draw the bubbles out of the caliper with a vacuum into the bleed bottle. Just pushing fluid through does not work with Hayes. I prefer the Hayes squeeze bottle. I find that using a syringe pushes the fluid through the system too fast resulting in the fluid blowing right past bubbles in the caliper nooks and crannys. It's not about how much fluid is pushed through the brake it's about taking your time and getting the brake in the correct orientaion so you'll get a good bleed.

    The MC bleed position differs between the HFX9 and the MAG. On the 9 you just flip it up so the bleed port area is pointing straight up. On the Mag you need to raise the front of the bike up and turn the handlebar to get the MC pointing up at a 45 deg angle upward. Any other position and you'll trap air in the system.

    Hope this helps.

    When in doubt, follow the Mfg. instructions. They do know more than anyone on any forum about the correct ways to service and install their products.

    (former brake guy)

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