Brake cut-offs, levers and rotors

A cut-off switch in the brake lever tells the controller to drop assist when you pull the brake. It is a small part and it is the difference between a controlled stop and a motor that argues with the pad. If the kit includes levers, they are part of the configuration. If it does not, the workshop has to add sensors that match this controller, not a random pair from a drawer.

The rotor and the arm

A hub wheel specifies a rotor size and a mount. A torque arm that occupies the same bolt as the caliper is a layout problem to solve on the bench, not during a test ride. Hoses that were the right length for a rim-brake fork are often short once a disc caliper and an arm are on the same blade.

• Confirm cut-off before the first road roll. Spin the wheel in the stand, pull the lever, watch assist die.
• Rim-brake wheels and disc-brake wheels are different products.
• A motor does not upgrade a glazed pad or a spongy hose.
• Cargo and trailers ask more of the same brakes. Budget the brake if the bike already needed one.