Safety & Regulations
Assist cut-off speed
What does Assist cut-off speed mean?
The road speed at which an e-bike's motor must stop helping: 25 km/h (15.5 mph) in the UK and EU, 20 or 28 mph in the US.
The assist cut-off speed is the speed above which an e-bike’s motor adds no power. It is the number that decides an e-bike’s legal class. In Great Britain the motor must not propel the bike above 15.5 mph, according to GOV.UK. EU pedelecs must cut off before 25 km/h. In California, Class 1 and 2 stop at 20 mph and Class 3 at 28 mph.
Can you ride faster than the cut-off?
Yes. The law limits the motor, not the bike. Above the cut-off you can go faster downhill or by pedaling harder, but every extra mile per hour comes from you, and air drag makes each one harder. Our guide to how fast electric bikes go shows the cut-offs side by side.
What happens if you raise it?
Raising the cut-off with a tuning kit moves the bike out of its legal class. Our fastest e-bikes guide shows the legal ways to get more speed.
Also known as: cut-off speed, assist cut-off, motor cut-off, assist limit
Related terms
- Class 3 e-bike A US e-bike whose motor helps only while you pedal and stops assisting at 28 mph (45 km/h). California also requires a speedometer.
- Speed pedelec An e-bike that assists up to 45 km/h (28 mph). In the EU it is a type-approved L1e-B moped, ridden with an AM licence under national moped rules.
- Electrically assisted pedal cycle The legal name for an e-bike in Great Britain: pedals that propel it, no more than 250 W continuous power, and no motor help above 15.5 mph.
- E-bike tuning kit A device or software change that raises an e-bike's assist cut-off speed. On public roads it usually takes the bike out of e-bike law.