For newer riders or those considering their first eBike, there’s often a lot of confusion surrounding pedal assist systems (PAS) and how they work.
Pedal assist systems offer an on-demand helping hand on hills and flats and allow you to adjust the amount of assistance.
For most of us, once we exit our teen years, we don’t want to work as hard to get where we need to go. eBikes with PAS help you get more enjoyment from riding a bike and still benefit from healthy activity (without breaking a sweat).
Well, unless you want to sweat, of course. There’s a setting for that too. You’re the boss.
Here’s a basic overview of how pedal assist works on an eBike. No worries; no electrical engineering degree required.
What is Pedal Assist?
On a regular bike, you’re pedaling strictly on people-power. Pedal assistance refers to a feature of an electric bicycle that lets the bike “help” you pedal using the bike’s electric motor. This assistance can deliver extra power at different parts of the drivetrain, depending on your bike’s setup.
Most eBikes, like the KBO pictured below, use a rear-hub drive. This means a motor in the rear wheel hub engages to assist your pedaling.
You continue pedaling at the crank, but a pedal-assist bike also spins the rear motor (in the KBO example, which makes pedaling easier because the bike is providing its as well, like a silent partner.
The (primary) alternative to rear-hub systems is mid-drive systems that provide assistance directly at the crank. You’ll typically find mid-drive systems only on higher-end bikes, whereas rear-hub systems are common at nearly all price levels.
A third option of front drive also exists but is less common. As the name suggests, front-hub systems power the front wheel to provide pedal assistance.
Pedal Assist Settings
Most eBikes offer several pedal assistance settings, typically ranging from zero (no assistance at all) to five (highest level of assistance).
You can think of these settings as power levels, meaning each setting tells the electric motor to deliver a specific level of electric power to make pedaling easier.
However, some bikes may offer fewer levels or more levels of pedal assistance.
In effect, a pedal assistance level is just a software switch that tells the motor to provide more (or less) power. Seen that way, an eBike manufacturer could theoretically offer a bike with a hundred power assist levels. PAS isn’t a gimmick, but more levels aren’t necessarily better.
Three to five pedal assist levels are usually sufficient for most riding situations. For example, the KBO Hurricane, a bike built with simplicity in mind, offers just three assist levels. By contrast, the Engwe Engine Pro offers five levels. And the Engine Pro reserves its regenerative engine braking feature for PAS levels one and two when the rider is doing most of the work.
Along with other factors, the level of assist you choose affects your electric bike’s battery life. You’ll get the longest range when using the lowest assist levels.
You’ll also get a better workout when choosing less assistance. Using an eBike on PAS one or two provides metabolic equivalents (MET) approaching those of riding a standard bicycle. METs are a measure of your body’s energy expenditure.
On many eBikes, higher PAS levels of four or five aren’t as useful as you might think in a lot of situations.
For example, with higher pedal assist mode settings, you might find that the bike is powering itself so fast that you can’t pedal fast enough to keep up.
If you’ve ever tried pedaling when going down a steep hill, it’s a similar situation.
You just run out of pedal because of the bike’s speed. Some riders refer to this condition as “ghost pedaling,” and it can be a bit dangerous because fast pedaling with no resistance makes the bike wobbly.
Generally, eBike makers put the PAS controls within easy reach of your thumb so you can change up or down as needed.
But you might find that all the assistance you need is available in the first few levels, especially if you’re a more leisurely rider.
Cadence Sensors vs. Torque Sensors
Some systems, such as Bosch, use multiple types of sensors to measure cadence, speed, and pedal power more than 1,000 times per second. Cadence refers to how fast you’re pedaling or the frequency of pedal strokes, while pedal power refers to torque or how hard you’re pedaling.
But most eBikes use a simpler setup that employs either a basic cadence sensor or a more-sensitive torque sensor. The latter is generally reserved for mid-range and higher-end eBikes due to cost constraints in the budget-conscious sector of the market.
These sensors tell the motor when to assist and — even more importantly — when to stop assisting.
Cadence sensors, the most common system used for low-cost and midmarket bikes, employ magnets to sense when the cranks are turning.
Both cadence sensors and torque sensors can work well. But torque sensors are more responsive, which translates to faster engagement for the pedal assistance.
Pedal Assist vs. Throttle
eBikes can have pedal assistance or a throttle, or both. A throttle lets you power the bike without pedaling at all. But not all bikes come with a throttle.
The lightweight KBO Hurricane, for instance, does not have a throttle. It’s built for a more active riding experience.
A throttle isn’t strictly necessary, and if you plan to use your eBike to stay fit, you might prefer a bike without one. But most electric bikes come equipped with one of two types of throttle: thumb throttle or motorcycle-style twist throttle.
You may find some differences in top speed between pedal-assisted riding and throttle-mode riding. Often, bike makers limit the speed of the bike to 20 MPH when using the throttle, although you might get the bike going a bit faster using pedal assist four or five.
Consider Your Riding Needs Before Buying
Electric bikes come built for different tasks and riding styles. Give some thought to how you’ll use your bike, including throttle and PAS considerations, before making a buying decision.
It’s better to make the right choice the first time. Buying the wrong bike for the way you plan to ride can be a costly experience due to depreciation.
Trading up is common as you become more experienced with eBikes, but it’s wise to invest some time in researching bikes and features to find the one that matches your needs. With the right choice, you’ll enjoy your ride for years to come.
Frequently Asked Questions
Is pedal assist better than throttle?
Pedal assist systems (PAS) serve a similar (but different) use case compared to a throttle. Pedal assistance allows the bike to help you pedal, but you’ll still do some work. Throttle controls, on the other hand, allow the bike to power itself without the rider pedaling at all.
Pedal assistance provides better battery life and gives the rider more exercise.
What does a pedal assist sensor do?
A pedal assist sensor detects whether you’re pedaling, signaling the motor to assist when you are, and telling the motor to stop when you’re not pedaling. Cadence sensors determine whether you’re pedaling by using sensing magnets. A second type of sensor called a torque sensor works by sensing how much pressure (torque) you’re using to pedal. Of the two sensor types, torque sensors usually provide faster and smooter response.