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Thread: new XT brakes

  1. #1
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    new XT brakes

    continued from hijacked thread

    here's where I'm at now, riding yesterday and the front was okay, the back pretty weak. Got the calipers hanging now and when I opened and squeezed I got a couple little bubbles out from the front and none from the back. What's interesting is the back feels much firmer with the block in the caliper, thinking that centering might have been the issue there. The front feels soft even after the squeeze that brought the bubbles out. Weird. Going to bleed the caliper first and if that doesn't do I'll push some oil up and through and see what happens.

  2. #2
    Team Blindspot
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    AW, I had the same problem with a mushy rear. I outlined how I bled it in the other post, but what jogged my memory about what I did was when you said you were bleeding with the yellow block. I did not bleed with the block, just the rotor. Then I pushed the calipers in a bit with the cover off the res. My assumption was the block was too big and the calipers had to travel too far to the rotor after bleeding that they felt mushy due to lower volume.

    This has worked well for me and for Jay's brakes.

    The other thing you mentioned, forcing more oil in the caliper side with a syringe. I've done that too and I think would achieve the same effect as bleeding without the block.(ie, getting more oil volume in the system) I got that tip from Dave at Redstone for ways to tune the shimano brakes even more.
    Astigmatic Visionary

  3. #3
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    I had to give up and give the front to a shop and run my backup brake. The rear was nice and firm all day but then mushed out on my last run. From asking around it sounds like there are places where the air bubbles get trapped in the system. Don't know how that would explain my rear brake.

  4. #4
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    What SW said.
    I did a similar thing to my two sets of XTR brakes.

    I bled them on the bike (OTB would probably been better) and worked with the rotor not the blocks.
    I pushed the pistons in first, then opened up the resivoir and had a bleed bag and wrench on the caliper end.

    I'd squeeze the lever and hold it, while letting fluid out the caliper bleed port, and closing it when the lever hit the bars. Then I'd pump the lever until I could get a bubble or three out of the resivoir, I'd repeat that a dozen times or so, perhaps stopping to tap the caliper and hose and resivoir with the handle of a screwdriver.(working my way bottom up. I'd also keep refilling the resivoir when it got lower.

    After all the bleeding, the biggest help was once I got the pistons to bite the rotor, I'd top off to the resivoir then close it up. That seemed to give it something to press against on the back end and firm up the lever.
    Faster is better, even when it's not.

  5. #5
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    Quote Originally Posted by Bikezilla
    I bled them on the bike (OTB would probably been better) and worked with the rotor not the blocks.
    Pretty much the same as the previous posts except I found off the bike works best and I use the orange pad spacer and some previously contaminated pads which were previously bedded in.
    More bikes than you can point a broken spoke at...

  6. #6
    FM
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    Just a thought, what are you using for mineral oil? In a bind, I recently bled my XT's with generic mineral oil. The viscosity was higher, the brakes felt mushy and lever return was slow, I was not stoked.

    I ended up buying a bottle of pentosin chf7.1 mineral oil, it works perfectly, better than the stock shimano oil and way cheaper.

    Also- I've made a bleed kit for my XT's that works awesome. Two small medical syringes and some vinyl hosing. I fill one with oil and connect it to the caliper, pushing oil up the line. As the master cylinder fills, I pull excess oil out of it with the other syringe (I generally keep going for 2-3 minutes after "no bubbles" just to be sure).The syringes make this all a 5-10 minute mess-free job. A spray bottle full of denatured alchohol is also very handy.

  7. #7
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    Quote Originally Posted by FM
    Just a thought, what are you using for mineral oil? In a bind, I recently bled my XT's with generic mineral oil. The viscosity was higher, the brakes felt mushy and lever return was slow, I was not stoked.

    I ended up buying a bottle of pentosin chf7.1 mineral oil, it works perfectly, better than the stock shimano oil and way cheaper.

    Also- I've made a bleed kit for my XT's that works awesome. Two small medical syringes and some vinyl hosing. I fill one with oil and connect it to the caliper, pushing oil up the line. As the master cylinder fills, I pull excess oil out of it with the other syringe (I generally keep going for 2-3 minutes after "no bubbles" just to be sure).The syringes make this all a 5-10 minute mess-free job. A spray bottle full of denatured alchohol is also very handy.
    I made that mistake once with maguras. Mineral oil for brakes is mineral oil for brakes.
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

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  8. #8
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    Quote Originally Posted by FM
    Just a thought, what are you using for mineral oil? In a bind, I recently bled my XT's with generic mineral oil. The viscosity was higher, the brakes felt mushy and lever return was slow, I was not stoked.

    I ended up buying a bottle of pentosin chf7.1 mineral oil, it works perfectly, better than the stock shimano oil and way cheaper.

    Also- I've made a bleed kit for my XT's that works awesome. Two small medical syringes and some vinyl hosing. I fill one with oil and connect it to the caliper, pushing oil up the line. As the master cylinder fills, I pull excess oil out of it with the other syringe (I generally keep going for 2-3 minutes after "no bubbles" just to be sure).The syringes make this all a 5-10 minute mess-free job. A spray bottle full of denatured alchohol is also very handy.
    Good info FM. I took an extra Sram syringe and designated it for mineral oil. What Dave at Redstone suggested to fine tune lever feel was once you get the whole system bled and closed up, attach the syringe to the calipier and open the bleen valve and force some more oil in. It did firm up the lever a bit.

    I may try your method for bleeding next time. Where did you find the Pentosin??
    Astigmatic Visionary

  9. #9
    FM
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    Quote Originally Posted by S-Works
    Where did you find the Pentosin??
    eBay! Here ya go.

  10. #10
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    Quote Originally Posted by FM

    ten-4. Just bought one.
    Astigmatic Visionary

  11. #11
    Baked Alaskan
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    Quote Originally Posted by FM
    Also- I've made a bleed kit for my XT's that works awesome. Two small medical syringes and some vinyl hosing. I fill one with oil and connect it to the caliper, pushing oil up the line. As the master cylinder fills, I pull excess oil out of it with the other syringe (I generally keep going for 2-3 minutes after "no bubbles" just to be sure).The syringes make this all a 5-10 minute mess-free job. A spray bottle full of denatured alchohol is also very handy.
    I did the same thing, only I used big food injector syringes. Fast, cheap and it works really well, what more could you ask for?
    The red couch has moved from Alaska to Florida...

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