Sensors, pedal assist and e-bike classes

A bike is labeled with a class and you wonder what that has to do with the sensor. The answer is in the wording of the law. Those words describe when the motor may help and where it must stop. Here they are, with the place and date.

This page quotes laws. It isn't legal advice. Rules on classes, ages, helmets and where you may ride differ by place, so check your own state or local rules.

The federal definition, United States

The federal law on low-speed electric bicycles, checked 2026-11-14, defines the term as a vehicle with fully operable pedals and an electric motor of less than 750 watts. It can have two or three wheels.¹

The law sets a top speed of less than 20 mph. That is on a paved level surface, powered solely by the motor, with a rider who weighs 170 pounds.¹

That text is about consumer product safety. It doesn't set the three classes.

The class wording in one state

Some US states use a three-class system. One example is West Virginia Code 17C-1-70, checked 2026-11-14.² It says:

• Class 1 has a motor that provides assistance only when the rider is pedaling, and that ceases to provide assistance when the e-bike reaches 20 mph.²
• Class 2 has a motor that may be used exclusively to propel the bicycle, and that isn't capable of providing assistance when the e-bike reaches 20 mph.²
• Class 3 has a motor that provides assistance only when the rider is pedaling, and that ceases to provide assistance when the e-bike reaches 28 mph.²

The same section defines a throttle as a device that controls the flow of power to the electric motor, for the purpose of propelling the e-bike.²

This is one state's wording. One reference says the classification of these bikes varies greatly, even across local jurisdictions.³ Look up your own state, province or country.

Where the sensor comes in

Read the Class 1 and Class 3 lines again. Assistance comes "only when the rider is pedaling." A bike has to notice pedaling to follow that rule, and that's the sensor's job. One reference says these bikes have a sensor to detect the pedaling speed, the pedaling force, or both.³

Class 2 is the difference. Its motor may be used exclusively to propel the bike, which is what a throttle does.² So pedal assist, driven by a sensor, and a throttle, driven by your hand, are two separate ways to ask the motor for power.

The law doesn't say which sensor type to use. A torque sensor and a cadence sensor can each tell the bike you're pedaling. See what an e-bike sensor does.

The same idea in the EU

Outside the US the wording differs. One reference says standard EN15194 treats a bicycle as a pedelec on three conditions. Over 6 km/h (3.7 mph), assistance only engages when the rider is pedaling. The motor cuts out once 25 km/h (16 mph) is reached. The motor's maximum continuous rated power is not more than 250 W; it can produce more for short periods.³ It adds that the UK has adopted the standard, as has the Australian state of Victoria.³

That's a different rule from the US classes. A bike sold for one place may not fit another place's definition.

What this page won't do

It won't tell you how to change a bike's limits. Class limits come from the law and from how the maker built and labeled the bike. Not sure of your bike's class? Read the label and the manual for your own model, then ask the maker or a dealer.

The way a sensor affects the feel of the help has its own page, on assist levels.