Recently swapped over my disc brake pads, but discovered that the pistons lightly scrape the rotor when not braking, and when I am braking it doesn't make much of a difference and it allows me to pull my lever all the way to the handlebar. Shimano Deore brakes btw

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    You need to bleed the air out of the brake system. See this video youtube.com/watch?v=DsqlEYJeLQU Commented Feb 28, 2015 at 0:50
  • Before you bleed the system, take the pads out again and try pushing the pistons back manually (head of a flat screwdriver, gently, can be effective). Sometimes the pistons get stuck and need pushing back. Could be this will make no difference and you'll need to bleed the system anyway, but if this works, it only takes a couple of minutes.
    – PeteH
    Commented Feb 28, 2015 at 12:03

1 Answer 1


If you can pull the lever all the way to the handlebar while not getting much braking force, then it is very likely that you somehow got air into the system somewhere, and you need to bleed the entire brake system.
Perhaps when you were changing the pads, you pulled the brake lever while the pads were removed, which would allow the pistons to come out too far ? That would let air into the caliper, which would lead to the symptom you described.

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