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Decided to give my old hard tail a brake bleed while I have nothing else to do, but can't seem to get them feeling right. They're the M780 XT's and the pads are about 1/3rd worn - so plenty of life.
I started by putting the bike in the stand at an angle so the levers are at the highest point. Then removing the pads and installing the bleed block, and then doing the fluid up, fluid down thing using syringes, and finally by flicking the lever to try to release any small bubbles.
In all the levers feel pretty good by this point, nice and solid. So I remove the funnel etc, put the pads back in and reinstall everything. Squeeze the levers and initially the lever comes almost back to the bars, but after a couple of pumps starts to feel better (pistons moving out a little?), more lever travel than I'd like but I'm guessing that's down to the worn pads.
I hang the bike up for the night, and next day come back and the lever is almost back at the bars again - but after a couple of pumps returns to a better position. Do I still have air in it? I've bled them this way several times now over the past few days and can't believe there's any more air left in there - what happens when the pads move out, do they leave a vacuum in the master cylinder? could this be causing it? Anyone got any ideas?
An there are no leaks, I've checked.
How do you hang the bike up?
Is it both brakes?
Did you change *all* the fluid, or just add a bit?
What fluid did you use?
Do a Marshy bleed:
Yep do a marshy bleed rather than messing with syringes. Also loosly cable tie the levers back to the grips overnight to allow air up.
Bike is hung up vertically by the back wheel - both brakes are affected, but the rear seems to be worse than the front - but I'd also say tht has slightly greater pad wear. Didn't change all the fluid, just a top up.
I've done a Marshy bleed too and made no difference.
When doing the lever/cable-tie thing, do you leave the cap off the master cylinder? or do you have to install the bleed funnel with a bit of fluid in there?
I don't, but I don't see why that wouldn't work, especially if there is a lot of trapped air. Raise the front of the bike to ensure no low points of brake line.
Also loosly cable tie the levers back to the grips overnight to allow air up.
This does not allow the air up in the way that people think, it closes the port into the reservoir so it actually keeps air in the master cylinder. What I think it does do is, if you cable tie them tightly, is to compress the air bubbles and makes it easier for them to travel up to the master cylinder. When you release the lever, the port into the reservoir opens and any air in the master cylinder will be pushed out into the reservoir.
Tap the brake lines. Tie wrap the levers back with the cover off. Leave it like this over night.my maguras did the same until I bledwith the levers on max reach. You could also try unbolting the calipers and them up high will tapping them and the lines