You’re rolling down a long hill on your e-bike, the speedometer passes 20, and the motor goes quiet. Nothing is wrong. That’s the assist cutoff doing its job, and the bike keeps rolling on gravity and your legs.
Most e-bikes in the US stop helping at 20 mph (32 km/h). Class 3 bikes keep going to 28 mph (45 km/h). Past those numbers, the motor adds nothing.
The three classes, side by side
The US sorts e-bikes into three classes. Each one sets the speed where motor help ends and says whether a throttle is allowed. Bosch has a plain-English rundown if you want the maker’s view.
| Class | How the motor works | Motor help ends at |
|---|---|---|
| Class 1 | Pedal assist only | 20 mph (32 km/h) |
| Class 2 | Throttle, works without pedaling | 20 mph (32 km/h) |
| Class 3 | Pedal assist only, speedometer required | 28 mph (45 km/h) |
States tweak this. New York sets its Class 3 limit at 25 mph, for example. Check your own state’s rules before you buy, because a Class 3 bike that’s fine in one place can be off-limits on a path in the next.
your state’s rules
Outside the US it’s simpler. UK e-bikes must stop assisting at 15.5 mph (about 25 km/h).
The cutoff is a ceiling, not an average
Here’s what the class table doesn’t tell you: how fast you’ll actually ride. Stoplights, hills, headwinds and a tired afternoon all pull your average well under 20 mph.
Your own legs still matter a lot. A new rider can hold 10 to 15 mph unassisted at a bit over 200 watts. A trained rider putting out 350 watts can average 25 to 28 mph on flat ground. The motor stacks on top of whatever you bring, up to the cutoff.
Some bikes are capped lower on purpose. Canyon’s city e-bikes assist up to 15 mph, a pace that suits stop-and-go commuting. If I were buying for a short urban commute, I wouldn’t chase a higher cap at all.
What really changes your speed
Watts and torque
Most e-bike motors run 250 to 750 watts. A bigger motor pulls harder off the line and holds speed better on climbs. It does not move the cutoff. The bike still cuts help at 20 or 28 mph to stay in its class.
Torque tells you more about how a bike feels. Bosch’s Active Line motor makes 40 Nm and assists up to 20 mph. Its Performance Line Speed makes 85 Nm and assists up to 28 mph. The second one gets you to the cutoff far faster.
Weight, terrain and assist level
A lighter rider on a lighter bike gets up to speed more easily. Smooth pavement beats loose gravel. Climbs fight the motor, and descents help it.
Tire pressure and wind count too, and a higher assist level drains the battery sooner. Our guide to reading the ebike display shows where your speed and assist level appear, so you can watch both.
Can an e-bike hit 30, 40 or 70 mph?
30 mph
Yes, but not on motor help. Most e-bikes are heavy, so on a steep descent they pass 20 or 28 mph from momentum alone. You just get no assist while you do it. Our piece on how fast a bike can go downhill covers the gravity side.
40 mph
Some machines sold as e-bikes can, with bigger motors and no cutoff. Motors can reach 1,000 watts and beyond, while many states cap e-bikes at 750 watts. Past that line, the law treats the thing as a different vehicle.
I’d skip any listing that promises 40 mph on the road without naming a class. Ask about registration and where you may legally ride it before you pay.
70 mph
That’s an electric motorcycle. It brings a motorcycle’s stopping distance and crash risk, and it doesn’t fit the e-bike classes at all.
Even 28 mph raises the stakes. A good set of ebike helmets and well-adjusted disc brakes matter more as the numbers climb.
Quick answers
How fast can an e-bike legally go?
In the US, motor help ends at 20 mph for Class 1 and 2, and 28 mph for Class 3, with state variations like New York’s 25 mph Class 3 limit. You can always pedal or coast faster than that.
How fast does an e-bike go without pedaling?
Only a Class 2 bike moves without pedaling, and its throttle stops at 20 mph. Class 1 and Class 3 motors need pedal input. If you ride a throttle bike, our tips on smooth ebike throttle control help with jerky starts.
How fast is that in km/h?
Class 1 and 2 assist ends at 32 km/h, and Class 3 at 45 km/h. UK bikes stop at about 25 km/h.
Does a bigger motor make an e-bike faster?
It makes the bike quicker off the line and stronger on hills. The assist cutoff stays where it is.
