Oops! Fix (most) hydraulic disc brakes
Why Bicycles Stack Exchange recommends it
Bicycles Stack Exchange answerers point people to it when someone has pulled the lever with the wheel off and the pads now rub or won't separate.
Recommended by 2 people across 2 different months, 2019 to 2023.
What it is
A roughly one-minute how-to from the Berm Peak channel showing what to do if you squeeze a hydraulic disc brake lever with the wheel removed. It explains that the pistons over-extend, then shows removing the pads and pushing the pistons back in with a simple tool.
What people said
Strong rec peachykeen · 2020-07 · Bicycles Stack Exchange · on “How do I separate hydraulic disc brake pads after pulling the brake while the wheel is off?”
I found this video to be extremely helpful in understanding the problem and solving it: I fixed my similar situation by removing my disc brake pads and pushing against the pistons behind them with a flat head screw driver. Using a credit card (or similar) to push against the pads wasn't enough for me.
Recommends Yossi G. · 2023-06 · Bicycles Stack Exchange · on “Why is my brake lever loose on my hydraulic disc brake i took my wheel off and pressed the brake now the brake lever is loose and touches the grips”
Oops! You should never squeeze the brakes while there is no disk between the pads. There's a plastic spacer available to slip between the pads when you have the wheel removed in order to safeguard against the condition you have created. [LINK] You did not specify whether the pads are contacting the rotor. If this is the case, then you've driven the pistons too close together, past the point where they should compress. Now they won't spring back. What you need to do is force those pistons apart. You need to remove the brake pads and use a thin tool, like a flathead screwdriver to force the pistons back to where they belong. This video demonstrates: Alternatively, you may have some air in the
Cites mattnz · 2019-05 · Bicycles Stack Exchange · on “Disc brakes not separating with force”
You normally need to take the pads out and lever the pistons. The pistons have a tight tolerance and jam easily. Its possible to do it with the pads in but you need a narrow enough tool to get all the way between the pads, that is strong enough to put the force need to retract the pistons. You also risk damage the pads. There cannot be too much fluid unless you bleed the brakes with the pistons extended. The fluid that pushed the pads out will return the reservoir, however this needs a happens quite slowly- you need to apply a gentle force to the pads for a long time rather than a brute force it. Worth watching