How to Use a Hydraulic Brake Piston Press

Pump the brake lever to release one or both pistons, and use your hydraulic piston press tool or wide-blade screwdriver wrapped in paper towel to clean, lube, and return them to their respective calipers.

The Park Tool PP-1.2 wedge-shaped Park Tool slides easily into hydraulic disc brake calipers to preset pistons when replacing or aligning pads, or other maintenance procedures. Made from durable tool steel, its ergonomic oversize handle offers user comfort.

Clean the Caliper

Squeaking brakes may be caused by any number of factors, including dirty pistons that do not retract after you release the brake lever. If this is indeed the case for you, cleaning these pistons is a relatively straightforward and can make a significant improvement to how your brakes perform.

Begin by taking off the wheel and locating the caliper (this varies among brake manufacturers), before inserting your Pedro's lever or bleed block with an "x" cut out to prevent one of the pistons from moving during cleaning.

Use isopropyl alcohol to disinfect both sides of the caliper with an appropriate spray. Wipe and dry thoroughly afterward. Afterward, dip a cotton swab in brake fluid that matches your system (DOT for Shimano/Magura or red mineral oil in Campagnolo systems). Apply a small dab to exposed portions of piston on one side, and repeat on the other.

Spread the Pistons

Hydraulic brakes utilize pressure to transfer energy and stop spinning discs by applying friction pads against them. Hydraulic pressure is created through pistons in its wheel cylinders which are powered by pedal action through its master cylinder.

Brake fluid pressure from the master cylinder travels through steel brake tubes to slave cylinders at each wheel, filling them and forcing pistons out to apply the brakes. Because slave cylinder pistons offer greater surface area 'pushing' force than their master counterparts, more force can be exerted upon applying them than with either.

When you release the brake pedal, springs in the master cylinder assembly return piston(s) to their rest positions. A wedge-style piston tool, such as Park's PP-1.2 Hydraulic Brake Piston Press is specifically designed to quickly and safely reset these hydraulic disc brake caliper piston(s).

Lubricate the Pistons

Under normal operation, brake pistons protrude slightly from a caliper in order to compensate for wear-and-tear on brake pads and to allow it to retract when pressure decreases (known as rollback).

Pistons don't usually require any lubrication as their movement against rubber seal is normally kept dry by bleed fluid in a hydraulic system; however, during installation/resetting and bleeding of systems additional lubrication will likely be necessary.

One method is using a special tool, like Pedro's hydraulic piston press; another option is using a flat, wide screwdriver. When employing either approach, be sure to protect both hands as the airflow could scatter dust around you during work.

Reset the Pistons

Hydraulic disc brakes utilize pistons in each caliper that push against the rotor to create friction and slow or stop your ride, with these pistons retracting back into their respective bores when you pull on the lever. As they recess further into their bores they also protrude out slightly more to account for wear on your pads; if this doesn't happen they could be stuck together and need pushing apart.

Resetting caliper pistons requires using either your hydraulic piston press tool or wide-blade screwdriver wrapped in paper towel to hold one of the pistons while you pump your brake lever, before cleaning, lubricating and pressing back into place after. Do this process with both pistons until they're back into their proper places.

The Park Brake Piston Press is an ideal solution for this job as it's specifically designed to do it. Crafted from strong tool steel for long-term use and featuring an oversize rubber handle for comfortable operation.