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  1. #1
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    New question here. Bike upside down = Bleeding ?

    I now have my first set of disc brakes (2004 XT hydraulics) and have some (probably) stupid questions:

    Question 1:
    Is it true I shouldn't turn my bike upside down? I've heard it might require to bleed the system... I usualy turn my bike upside down when I wash it or when changing a flat. Do I have to start new maintenance practices or am I ok until something goes wrong (air in the lines, which I don't know how that happens yet)?

    Question 2:
    My rear brake has an issue. One pad is a little outer than the other, looks to be touching the rotor but doesn't seem to stop the wheel tough. When I brake, both pads move the same distance toward each other but the problematic pad pushes the rotor a bit, making it flex...

    Will this cause premature wear of the rotor or the pad? Should I just let it be or should I bring the bike to my LBS for a fix? I understand how to fix this according to Shimano's manual but am afraid of opening the oil reservoir on the lever... Now's the time to link both questions: Will opening the oil reservoir make air come into my system? Do I need to add oil?

    I don't mind mechanical fooling around but this would be my first experience with hydraulics.

    DAN.GEROUS.NET : MOUNTAIN BIKING : CYCLOCROSS : ROAD :

  2. #2
    Bodhisattva
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    Dr.J...

    Question 1: turning the bike upside down will not cause air to enter the system. However, if air is already trapped in the system, turning the bike upside down may dislodge that small bubble & cause it to migrate to a place where it does interfere with brake function. So if your brakes were properly setup & bled, you're OK.

    Question 2: the pads will not wear prematurely. On most brake systems it's difficult to get the rotor to align perfectly between the pads. So long as it doesn't rub excessively it's OK.
    Life....the original terminal illness

  3. #3
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    Thanks

    Quote Originally Posted by The Squeaky Wheel
    On most brake systems it's difficult to get the rotor to align perfectly between the pads.
    Or is it to align the pads perfectly around the rotor?
    One piston seems to protrude more than the other, that's why I think I should push it back in, but as I said, I'm a newbie as far as hydraulics go. Thanks for clearing things up...

    DAN.GEROUS.NET : MOUNTAIN BIKING : CYCLOCROSS : ROAD :

  4. #4
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    i just got a bike with 2004 XT.

    It does say in the manual that you aren't supposed to keep the bike upside down, but whatever. i think even if there was an air bubble, you could flip it right side up and pump the brakes a bit, and get the bubble to come up into the resevoir anyways.

    yeah something you can do to even out the pads...

    take out the brake pads, but be careful not to touch them - oil is death to pads. then you can just push the pistons back without opening the resevoir. then you can loosen the post mount bolts so that the caliper can move a little. put the pads back in and depress the the brake to center the caliper on the rotor. while the brake is depressed on the rotor, tighten the post mount bolts. and hopefully the pads should be centered.

    you'll always get some rub tho, it's hard to get rid of entirely..

    you might as well buy a bleed kit and learn how to do it yourself. LBS pricing is outrageous and I work at a shop.

    GL,
    -don

  5. #5
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    Quote Originally Posted by blehargh
    i just got a bike with 2004 XT.

    It does say in the manual that you aren't supposed to keep the bike upside down, but whatever. i think even if there was an air bubble, you could flip it right side up and pump the brakes a bit, and get the bubble to come up into the resevoir anyways.

    yeah something you can do to even out the pads...

    take out the brake pads, but be careful not to touch them - oil is death to pads. then you can just push the pistons back without opening the resevoir. then you can loosen the post mount bolts so that the caliper can move a little. put the pads back in and depress the the brake to center the caliper on the rotor. while the brake is depressed on the rotor, tighten the post mount bolts. and hopefully the pads should be centered.

    you'll always get some rub tho, it's hard to get rid of entirely..

    you might as well buy a bleed kit and learn how to do it yourself. LBS pricing is outrageous and I work at a shop.

    GL,
    -don
    Great tip, but the piston wont go back in unless I push harder than I want to try.

    And I do want to learn how to do the job myself, altough my LBS wont charge me for correcting this particular situation... I have a good relationship with them. I guess they would charge for the whole bleed tough.

    So I'll just have to find a small enough philips screwdriver to open the reservoir and do the job as is described in the Shimano manual. Oh, and a bike stand would be helpfull.
    Do I need the pad spacer described in the manual or can I just, once the piston is back in, put the wheel back, close the thing, pump it to check and voilà?

    DAN.GEROUS.NET : MOUNTAIN BIKING : CYCLOCROSS : ROAD :

  6. #6
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    i'm not 100% sure about this, but if you're just gonna pop open the resevoir cap, push back the pistons, fill the resevoir, and then recap it - then you probably don't need the spacers. i think it's more for if you want to do the entire bleed and pump the levers a couple times to get the air out. someone correct me if i'm wrong here.

    but seriously, i wouldn't worry about pushing the pistons back without opening the resevoir. think about it, all that braking force that the pistons have to put on the pads when you brake - not to mention heat build up. they'll be OK. and it's a hella lot less messy. i had to extert a good bit of force, but not extreme i'd say...

    also, have you ridden a lot with the bike? disc will take some time to bed in so maybe if you just ride awhile, it'll wear down the pads okay. honestly tho, it sounds like you're making a mtn out of a molehill.. disc brakes rub, rotors will warp, your brakes will get contaminated and squeal like a mad pig. don't sweat it if your pistons are just a little uneven. they'll be OK .

    GL,
    -don

  7. #7
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    Thanks don

    Quote Originally Posted by blehargh
    i'm not 100% sure about this, but if you're just gonna pop open the resevoir cap, push back the pistons, fill the resevoir, and then recap it - then you probably don't need the spacers. i think it's more for if you want to do the entire bleed and pump the levers a couple times to get the air out. someone correct me if i'm wrong here.

    also, have you ridden a lot with the bike? disc will take some time to bed in so maybe if you just ride awhile, it'll wear down the pads okay. honestly tho, it sounds like you're making a mtn out of a molehill.. disc brakes rub, rotors will warp, your brakes will get contaminated and squeal like a mad pig. don't sweat it if your pistons are just a little uneven. they'll be OK .
    Well I don't think I need to do the entire bleed at this point. The bike is very new. So maybe riding it a while like this will make things fine.

    I must be making a mountain out of a molehill...

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  8. #8
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    heh, it's all good. it's your baby. i understand. btw, what did you get?just curious
    -don

  9. #9
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    ... and if we just ... Cake

    Quote Originally Posted by blehargh
    heh, it's all good. it's your baby. i understand. btw, what did you get?just curious
    -don
    Gary Fisher Cake 1_DLX. I didn't get to really try it yet because of the snow and too much work, can't wait to hit the trails! SPV does work nicely on the smooth streets tough...

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  10. #10
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    mm

    Quote Originally Posted by Dan Gerous
    Gary Fisher Cake 1_DLX. I didn't get to really try it yet because of the snow and too much work, can't wait to hit the trails! SPV does work nicely on the smooth streets tough...
    Sounds like a basic alignment issue of the caliper vs rotor. Use some washers and play around. I trust myself more than a bike shop so I re-bleed my brakes by myself.
    [SIZE=5]For the love of Oi[/size]

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  11. #11
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    Nice. We've got some Cake's in the shop, and they do look pretty damn sexy. hope the weather clears up for ya there to go out on your ride. I got a Palomino XV about 3 weeks ago, but I'm out in cali so the weather's good.

    lemme know how it rides. i'm curious..

    -don

    p.s. no need for washers since the XT calipers are all post mount anyways.

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