919 Rear brake help! - Wrist Twisters
 
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post #1 of 8 Old 03-23-2009, 03:49 PM Thread Starter
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919 Rear brake help!

Having alittle problem with my rear brake, I put a new galfer rotor on it and pads over the winter, and bled the brakes. I took the bike out for the first time yesterday and when the bike is stopped, the rear pedal has a firm feel and i can see the piston pushing the pads onto the rotor, however when I'm riding the bike, the pedal goes the whole way down and I have pretty much no rear brakes.

I can't imagine there being air in the line, I spent a good hour bleeding the rear line (I figured it was air in the line). I haven't had the chance to take it all apart, I was wondering if this had happened to someone else and they could narrow it down for me?

Thanks,
Chris

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post #2 of 8 Old 03-23-2009, 04:37 PM
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first guess is you misinstalled an axle spacer, assuming you bled them correctly.

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post #3 of 8 Old 03-23-2009, 04:40 PM
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Originally Posted by Epicsoldier View Post
Having alittle problem with my rear brake, I put a new galfer rotor on it and pads over the winter, and bled the brakes. I took the bike out for the first time yesterday and when the bike is stopped, the rear pedal has a firm feel and i can see the piston pushing the pads onto the rotor, however when I'm riding the bike, the pedal goes the whole way down and I have pretty much no rear brakes.

I can't imagine there being air in the line, I spent a good hour bleeding the rear line (I figured it was air in the line). I haven't had the chance to take it all apart, I was wondering if this had happened to someone else and they could narrow it down for me?

Thanks,
Chris
I've had that happen to me on a dirt bike after a crash , which resulted in a bent rotor. what that did, as the wheel spins the rotor pushes the calipers apart, so when you apply the brake , the calipers have to close the gap before any pressure is applied to the rotor . that's why your pedal goes all the way down, and it only happens when the bike is in motion. If I were you, I'd raise the back and make sure the new rotor does not wobble .The only other thing I can think of, is over heated brake fluid due to excessive use of rear brake

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post #4 of 8 Old 03-23-2009, 05:44 PM
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+1 on bent rotor, but more than likly misalinged, dont know if it is possible but it could be, wheel outa line go back to what you did to it and look at anything that moves when the wheel spins.

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post #5 of 8 Old 03-23-2009, 05:55 PM
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how many times did you do it? did you seat the pads against the rotor before going out on a ride?

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post #6 of 8 Old 03-23-2009, 07:20 PM Thread Starter
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okay I'll have to take the rear back apart I guess , and I put about 40kms on it so far, the pads are touching the rotor, I can see the drag marks on the rotor. What do you mean exactly by "seating" them?

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post #7 of 8 Old 03-24-2009, 11:03 AM
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it's not a seating issue. and you'd see/hear if it was a bent rotor, typically. if you have a stand, spin it on the stand by hand and look/listen to rotor. if the drag changes. spacer/washer issue is still my focus. unless/until new data becomes available.

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post #8 of 8 Old 03-24-2009, 11:16 AM
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Bent or incorrectly installed rotor. If you've got good feel when stopped, but not when moving, the rotor is moving the pads back in.

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