Master Cylinders - Brake | The Moto Store

Master Cylinders

A brake master cylinder does one job: turn lever or pedal travel into hydraulic pressure. When the piston seals inside it wear, the lever goes soft, pumps up after a few squeezes, or slowly sinks to the bar while you hold it. Nine times out of ten that is a seal problem, not a bore problem, and a rebuild kit puts it right for a fraction of the cost of a new assembly. This page carries master cylinder rebuild kits for front and rear brakes on dirt bikes, ATVs, and street bikes from Psychic, SPI, Shindy, and ProX; browse the full list under Master Cylinder Rebuild Kits.

Front and rear kits are not interchangeable. The front master cylinder on the handlebar and the rear one at the pedal use different piston diameters, so kits are sold by position and by model. Check the fitment list on the product page against your make, model, and year, and note whether the kit is for the front or rear before ordering — Shindy and Psychic label this in the title.

Inspect the bore before you buy. Pull the old piston and look at the cylinder wall. Light staining cleans up with brake fluid and a lint-free cloth; pitting or scoring means the seals will fail again, and the whole unit needs replacing. Kits typically include the piston, cups or seals, spring, and circlip; some add the dust boot and reservoir diaphragm, so compare contents if your old boot is cracked.

Finish the job properly. Fresh DOT fluid of the grade printed on the reservoir cap, a full bleed, and a look at the brake lines and brake calipers — a caliper with a seized piston will make a freshly rebuilt master cylinder feel bad on the first ride. Wheel cylinder kits and drum seals live under Brake Repair Kits.

Read our guide to choosing between a master cylinder rebuild kit and a replacement.

Free shipping on orders $50+ (Lower 48).