Coaster Brake and E-Bike Conversion: What Works

A coaster brake is the most common reason a conversion does not work. The simplest solution is a front motor, because the rear wheel with coaster brake then stays untouched. Rear motors generally rule themselves out, and with mid-drives the coaster brake is often lost unless a suitable variant exists.

Why the coaster brake gets in the way

The coaster brake sits in the rear hub, usually together with hub gears. You brake by pedalling backwards. That only works if crank, chain and hub have a continuous connection.

In an e-bike conversion this interferes in two ways:

• Rear motor: The motor replaces the rear hub. Then there is no coaster brake any more, and the hub gears go too. Hub gears and a coaster brake rule out most rear motors.
• Mid-drive: The motor sits at the bottom bracket and has a freewheel. Back-pedalling often no longer brakes, because the force does not travel back to the hub.

What works, what does not

Coaster-brake variants exist for individual mid-drives, for example for the TSDZ2, and Pendix advertises compatibility. That is an assumption Fabio is still checking. Ask before buying whether your model can be combined with your bike.

The brakes have to be enough anyway

An e-bike is heavier and faster than your old bike. If you rely on the coaster brake alone, braking power is often too weak, and you need extra brakes front and rear. Rim brakes reach their limits with extra weight and speed, and hydraulic disc brakes are best (GIGA). More under brakes.

With a coaster brake at the rear and a new brake at the front you combine two systems. That can work, but test it on every ride.

Options if you have a coaster-brake bike

1. Front motor. The coaster brake stays. In return the weight sits at the front, more in motor types compared.
2. Mid-drive with coaster variant. Only if your bottom bracket fits (measure your bottom bracket).
3. Modify the bike. Fit a rear wheel with derailleur gears and hand brakes. That is a lot of work and often costs more than a used e-bike.
4. Leave it. If no solution is economical, buy used instead.

Safety in daily use

On an e-bike the motor must switch off when you brake. Without cut-off the motor can keep pushing while you brake. That is why you need brake levers with cut-off or sensors, see brakes. With a coaster brake you do not have that lever, so the cut-off has to work through the pedalling motion. Ask the dealer how the kit handles this.

That a conversion counts as tampering and some workshops refuse it hits coaster-brake bikes especially hard (Fahrrad XXL).

Checking your bike

1. Look at the rear wheel. Does the hub have a brake rotor or is there a brake lever on the rear triangle? Then it is not a coaster brake.
2. Pedal backwards. If the bike brakes, it is a coaster brake.
3. Clarify the gearing. If the gears sit in the hub, it is a hub gear. That rules out many rear motors.
4. Ask the dealer. Send bike, hub model and the motor you want. An honest dealer will tell you whether it works.

The configurator takes some of these questions off you. If in doubt, still talk to a workshop before you order.

How reliable is this?

The general statement that hub gears and coaster brakes rule out most rear motors, and that a freewheel in the mid-drive often disables the coaster brake, is an assumption Fabio is still checking. The statement on braking power comes from the source named.

Does a conversion fit your bike?