brake block

brake block (plural brake blocks)

1. (on a bicycle) One of two small blocks fitted to a brake caliper, which rub on the wheel rim when the brake is applied.
2. (rail transport) A block fitted to locomotives or rolling stock, which rubs on the steel tyre of the wheel when the brake is applied.
   • 1959 March, “The 2,500 h.p. electric locomotives for the Kent Coast electrification”, in Trains Illustrated, page 124:

     There are two brake blocks per wheel of the locomotive, and each brake block is actuated by its own cylinder, which obviates rigging (except to the hand parking brake).

   • 1960 February, “The first of London's new Piccadilly Line trains is delivered”, in Trains Illustrated, page 93:

     Braking is by non-metallic brake blocks throughout, two to each wheel.

3. A block (perhaps wooden) used for braking a horse-drawn vehicle.

• “brake block”, in Lexico, Dictionary.com; Oxford University Press, 2019–2022.