How Pedal Assist Works on an E-Bike

how ebike pedal assist works

What sets e-bikes apart from traditional bikes is the motor. An e-bike’s motor is responsible for powering the bike’s pedal assist system (PAS), which helps propel the bike forward while you’re pedaling.

Different bikes have different levels of pedal assist, varying the amount of pedaling support they can give you. Some bikes also have a throttle assist function, which powers the bike forward even when you aren’t pedaling.

But just how do these cutting-edge features work? Below, we give you the technical details on how pedal assist and throttle assist operate and elaborate on the differences between the two.

What is pedal assist (pedelec)?

Aside from having a hub motor or mid-drive motor, the No. 1 feature that sets an electric bike apart from a regular bike is pedal assist. With pedal assist, the e-bike motor only engages while you’re pedaling, but also amplifies your pedaling power. This type of bike is also called a pedelec (short for pedal electric cycle).

How does pedal assist work?

Pedal assist is controlled via a sensor, which is built into the bike motor’s drivetrain. The sensor monitors how much pedal power you’re providing and signals to the motor how much help to give you based on your chosen PAS level.

The two types of pedal assist sensors are cadence sensors and torque sensors. We’ll go over the differences next.

Cadence sensors

Cadence sensors are the most basic sensor system for a pedal assist bike. A cadence sensor uses magnets installed next to the pedals to determine when you’re pedaling. If the sensor detects that you’re pedaling, it activates the PAS.

E-bikes with cadence sensors are fairly common and affordable. However, they’re also less refined than other options. You may experience a jerkier bike ride, and the motor is more likely to cut out occasionally.

Torque sensors

While a cadence sensor is essentially an on/off switch for an e-bike motor, a torque sensor is a bit more complex. It tells the motor not only if you’re pedaling but also how hard you’re pedaling. Using this, the motor adjusts according to pedal power.

Torque sensors function in two ways. Rear torque sensors rely on a precision strain gauge, which moves every time you push down on the pedal, signaling to the motor how much pressure you’re applying.

Bottom bracket sensors rely on a magnet. Metal shafts between the bike’s cranks — the metal arms connected to the pedals — have a magnetic field. The bottom bracket sensor tracks the magnetic field of the cranks as they move, converting it to a voltage signal and communicating that voltage signal to the motor.

Torque sensors are more complex than cadence sensors. They offer a smoother ride, which makes them preferable. That said, bikes with torque sensors are also more expensive.

Pedal assist vs. throttle on an e-bike

Some e-bikes have only pedal assist, while others have both pedal assist and throttle assist. So, what’s the difference? Here’s what to expect in pedal assist versus throttle assist e-bikes.

Pedal assist e-bikes

With a pedal assisted e-bike, the motor kicks in and helps only when the cyclist is pedaling. The basic characteristics of pedal-assisted e-bikes include:

  • Multiple assist levels. Pedal assist can vary from offering very minimal to maximum support. Although it's easier to cycle with max support, it also drains the battery faster.
  • Sensor-controlled variation. Either a cadence sensor or torque sensor is used to control the PAS. Torque sensore-bikes are usually smoother to ride but more expensive.
  • More flexibility. Pedal-assisted e-bikes don't face the same harsh restrictions as throttle-assisted e-bikes. Some jurisdictions don't allow throttle assisted e-bikes in normal bike lanes, for example.

Throttle e-bikes

With a throttle e-bike, the motor kicks in and propels the bike forward even when the cyclist isn’t pedaling. Here are some key features of a throttle function:

  • On/off function. Most e-bikes have some kind of switch or lever on the handlebars to engage the throttle function. The rider can simply switch the throttle assist on or off.
  • Self-controlled variation. With throttle assist, riders can set how fast they want to go. For example, you can accelerate or decelerate using a thumb-controlled throttle at the handlebars.
  • More legal restrictions. E-bikes with throttle assist generally face more legal restrictions, such as where you’re allowed to ride. For instance, a throttle assisted e-bike may not be permitted on normal bike paths.

E-bikes with both pedal assist and throttle

Class 1, class 2, and class 3 e-bikes all have pedal assist. Class 1 e-bikes, also called pedelecs, never have throttle assist; to engage the e-bike motor, you always have to be pedaling. Higher classes of e-bikes may also have throttle assist.

It’s up to you whether you want an e-bike with pedal assist alone or one with with pedal assist and throttle assist. Each class has its pros and cons. Velotric’s class 2 e-bikes come with a five-level PAS and throttle assist, giving you the best of both worlds.

Pedal assist levels explained

Most e-bikes have different levels of pedal assist. If you choose a lower level of pedal assist, you do more of the brunt work yourself. If you opt for a higher level of pedal assist, the motor does more of the work for you.

Here’s what you can expect from a standard five-level PAS:

  • Level 1. Expect little assistance. This is ideal for conserving battery power. You likely won't exceed top speeds of about 10 mph.
  • Level 2. Expect light assistance, which can be helpful for maintaining the pace in urban areas. Again, don't expect top speeds beyond 10 mph.
  • Level 3. Expect a noticeable level of assistance, enough to help with slight inclines. You might find yourself going at speeds of up to 15 mph.
  • Level 4. The pedal assist will be obvious at this point. It will feel like the bike is almost pedaling itself (although it's not — that's what throttle mode is for). You may reach speeds of up to 20 mph, depending on the motor power.
  • Level 5. This is the most amount of assistance you can get from your motor. Most bike motors cut out at speeds of 20 mph when the PAS is engaged at this level, although some may go as fast as 28 mph.

While a high level of pedal assist can make for a less strenuous cycling experience, beware: This will place more strain on the motor, wearing out e-bike batteries faster. As a result, your bike’s range (how far it can go on a single charge) will decrease.

Other factors that can reduce your e-bike range include a heavier load and a more aggressive riding style (like going uphill). For example, the Velotric Nomad 1 e-bike has a range of 55 miles, while the Discover 1 has a range of 65 miles. The fat tire Nomad 1 is a heavier e-bike, hence the shorter range. However, this is due to its greater power that lets you take on tougher terrain.

Is pedal assist or throttle better for an e-bike?

So, what’s the best electric bike: one with a PAS, or one with throttle assist? Pedal assist and throttle assist each have their pros and cons. With pedal assist, you’ll still be able to get some exercise and help power the bike forward — but you may get tired out faster. With throttle assist, you can relax more — but you’ll drain the battery faster.

Velotric’s e-bikes feature both a five-level PAS and throttle assist. You can switch between functions depending on your needs. For example, engage the PAS at a high level for climbing a steep hill, then cruise with throttle assist on a flat surface.

Velotric e-bikes feature throttle and pedal assist for the ultimate ride

If you want an e-bike that gives you the freedom to choose between pedal assist or throttle assist, Velotric has you covered.

The Discover 1 is a great commuter bike, perfect for city riding. Want to explore the great outdoors? Try the Nomad 1. This fat tire e-bike is ideal for cyclists who want to go off-road (on unpaved bike paths, for example). Both bike models have five pedal assist modes and throttle assist.

Schedule a test ride today to find your electric bike.


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