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XTR brake bleeding
#1
Today I'm going to have a go at bleeding my own brakes, ha!

The reason is basically one of the piston caliper disc thingys on the rear brake isn't returning correctly leaving the brake caliper rubbing the disc - they are centred and aligned. I can push the piston back with the 'sailor patented caliper/piston reset tool' (or spatula as its known to his GF!) but as soon as I pull the brake it feels spongy and the piston then doesn't return. Are they knackered?

Is this a job I can tackle myself?

I Have a bleed kit, some dot fluid and some mineral oil and some olive oil.

The first question is: as these are shimano XTR's do I use mineral oil or dot fluid?

Much advice will be required and there will be loads of posts asking inane questions, so be prepared!

I have the bike in the workstand, levelled and ready to go.

just awaiting advice from the collective genius' on here!

Any help and advice is greatfully received.
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#2
you will find it easier and get better results if you bleed using a syringe on the caliper. Half fill syringe, attach then gently pull on plunger to suck air out, then push down and keep repeating until no more bubbles appear. Make sure any pad adjustment/lever reach dials are wound out. Also angle the bike in the stand so that the caliper is higher than the lever.

Regardless of which method you use, from the caliper or the standard add oil to lever and bleed out of caliper its worth de-gassing the fluid first. For this you will also need a syringe, just half fill it, block off the end and pull the plunger a few times until most of the bubbles have stopped appearing (you cant get rid of all of them).

If you dont have a syringe then just follow standard shimano instructions, you should still get a reasonable bleed, just not quite as good. Shimano normally use mineral oil, DOT will ruin all your seals if its a mineral system.
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#3
Okay cool. On the brake lever there is a cap with XTR on it do I have to remove that before/during/commencing bleeding
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#4
[quote="]you will find it easier and get better results if you bleed using a syringe on the caliper. Half fill syringe, attach then gently pull on plunger to suck air out, then push down and keep repeating until no more bubbles appear.[quote"]
OMG, I got so obsessed with removing every last bubble when I used this method :o
It's amazing how much air the fluid can give up...
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#5
[quote="impished"][quote="impished"]you will find it easier and get better results if you bleed using a syringe on the caliper. Half fill syringe, attach then gently pull on plunger to suck air out, then push down and keep repeating until no more bubbles appear.
Quote:OMG, I got so obsessed with removing every last bubble when I used this method :o
It's amazing how much air the fluid can give up...

lol.... it works a treat though doesnt it!
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#6
"jellylegs" Wrote:Okay cool. On the brake lever there is a cap with XTR on it do I have to remove that before/during/commencing bleeding

really need to see a pic but it sounds right yes, under the cap is the fluid reservoir. You put fluid in here, open the bleed nipple on the caliper pull the lever slowly to the bars, close the bleed nipple, release lever slowly, then repeat until bubbles stop appearing out of the caliper. This should give you an ok bleed, especially if you de-gass the fluid first. Just using a syringe on the caliper and forgetting the lever will give better results, especially as it allows you to pressurise the system slightly which the standard method doesnt.

Dont get oil on the brake pads!! In fact its safest to remove the wheel and pads and just space the pistons out with either a proper spacer or piece of wood or spatula etc. Worth attaching some plastic hose to the bleed nipple and bleeding the fluid into a jar, it makes it easier to see bubbles and reduces risk of spilling oil where you dont want it.
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#7
will you be testing it anywhere later?
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#8
Just done the fronts and all appears to be going well. How much air can fluid contain?
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#9
Something I forgot to do before bleeding was push the pistons in. In my very limited brake bleeding experience this is important. As for the piston not returning, I read this part somewhere, push them out and clean around the edges as much as possible with brake fluid / whatever you're using.
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#10
I bled mine from Caliper end also, from memory, I de-gassed the line as much as possible and then removed cap at lever end to force fresh fluid through.

Its actually fairly easy to do, but with the non-shimano kit, can be a tad messy.

Dont forget to clean the f*ck out of surrounding areas if any spillages onto paintwork.
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