Electric Bike Motor Guide
There are many different types of e-bike motor. They all share key design principles, but each have their own unique characteristics. All Tredz electric bikes feature pedal assist motors and that comply fully with UK law*, so you can ride our e-bikes safely anywhere you ride a regular bike. You get a boost to your natural pedalling power when you turn the cranks but this stops while you are coasting.
Motor Power
How much power do I need?
All legal electric bikes have pedal assist motors. That means the motor adds to your natural pedalling power helping you and the bike to move more easily. The amount of power that the motor adds to your natural pedalling power dictates how easy it is to ride.
More power = easier cycling. More powerful motors make it easier to ride. This is especially noticeable when riding up hills. The most powerful e-bikes make it easy to cycle quickly up the very steepest gradients.
This power does come at a cost. More powerful motors are bigger and heavier. They also use more electricity so require a larger battery. This is why more powerful e-bikes are heavier than less powerful ‘lightweight’ electric bikes.
Read our electric bike battery guide to find out more about e-bike batteries.
Why is torque important?
Torque is the number that gives you the best indication of the power that an e-bike will produce. Measured in Newton Metres (Nm) Torque is a measure of rotational force. The maximum torque that a motor produces tells you how much power the motor can add to your natural pedalling power.
The most powerful e-bike motors have a Max Torque of 90Nm. These motors will get you up the very steepest off-road climbs with ease. For Urban cycling 40 Nm is enough for most peoples’ needs.
Power delivery
A crucial aspect of a good e-bike is the software that controls the power. Fortunately, all the big e-bike brands have refined the power delivery of their motors, so they deliver the power smoothly and intuitively as you pedal.
The best e-bike motors sense how hard you’re pedalling and regulate the power accordingly. Pedal hard and they give you more power, ease off a bit and the power eases back too. Motor brands may have a slightly different feel, but all the big players offer very smooth power delivery as you pedal.
Power modes
Most e-bikes offer different power modes that you can switch between as you ride. This allows you to control how much power the motor will give you as you pedal. A higher power mode makes pedalling easier and will allow you to ride up hills faster. Using a lower power mode means will make pedalling a bit harder but uses much less battery power, so you can ride further on a single charge.
Displays and remotes
The power modes are controlled by buttons on the frame and/or a remote switch on the handlebars. Remotes on the bars are most convenient as you can easily shift between modes while you’re riding.
These controls are combined with a display to tell you which mode you’re in and how much battery charge remains. Displays vary from subtle LED lights to full colour screens. Many e-bike displays can show additional information like estimated range, speed and cadence.
* UK law requires that all electric bike motors are pedal assist, have a nominal power rating of 250 Watts, and only offer assistance up to 15.5mph (25Kmh).
Types of E-Bike Motor
The type of motor that’s best for you will depend on the terrain you want ride, your riding style, and your budget. For example, if you want to ride up steep off road climbs as fast as possible then a full power crank drive motor is what you need. But most people don’t need this much power for easy urban cruising, so a lighter weight and more affordable hub drive motor may be a better choice for city cycling over short distances on flatter terrain.
Crank drive Vs hub drive
There are two basic types of pedal assist motor fitted to electric bikes: hub drive and crank drive.
Positioned inside the wheel, hub drive e bike motors turn the wheel directly and allow for a more conventional frame design. Hub drive motors are usually the least powerful but they’re also lighter weight and less expensive.
Crank drive e bike motors, aka mid drive motors, offer more powerful assistance and are positioned in the bottom bracket area of the frame. These add their power directly through the chainset. As they’re centrally positioned e-bikes with crank drive motors are stable and nicely balanced.
Full power vs lightweight
Across all the cycling disciplines two different types of crank drive e-bikes are emerging: full power and lightweight.
Lightweight motors are gaining the upper hand for road e-bikes because you spend more time riding above 15mph on the road. Lightweight e-bike motors make the bike much easier to pedal when the motor isn’t engaged but still offer good pedal assistance on the climbs where you need it most. There is a much more even split with mountain bikes as there are costs and benefits with each system.
Full Power Motors
Will get you up to the top of the hill as fast as possible so you can save all your energy for the descents.
Full power electric bikes have the most powerful motors. These draw the most power so require high-capacity batteries, some as large as 900Wh. Full power e-bikes are the fastest up hills and tend to have the longest range as they have much bigger batteries.
The downside of full power e-bikes is that they are heavy. This isn’t a problem when pedalling, but if you want to manoeuvre the bike, lift it onto a bike rack or ride tight technical terrain, this extra weight can be a problem. This is where lightweight e-bike come in.
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Lightweight Motors
Feels more like a regular bike but gives you the extra assistance you need for climbing and big days out.
A lightweight or mid-power e-bike still uses a crank drive motor but may have half the power of it’s full-power sibling, but this is still enough to offer a significant boost to your natural pedalling power. As they don’t draw as much power as a full-power e-bike they don’t need as big a battery.
Lightweight e-bikes can be up to 5Kg lighter which makes a significant difference. Lightweight e-bikes tend to feel more like a regular bike when riding, handling is nimbler, but they lack that planted feel that heavy full power e-bike offers.
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Motor Brands
Bosch are the original e-bike motor brand and are still one of the most popular today. They have a range of different motors offering support levels tailored to specific applications. The motors can be combined with different Bosch remote and display units as well as battery capacities. Bike brands will choose the combination of motor, battery and display to suit their e-bike requirements.
All Bosch motors offer 4 support levels, and these are matched to the motor type and bike that it’s fitted to. Most interesting is eMTB mode, a smart support function that tailors the support levels to rider input. This allows for efficient riding without sacrificing high-end performance. The motor characteristics can be fine-tuned using a Bosch app.
City Bikes
Bosch Active Line and Active Line Plus motors are most popular on City bikes. These crank drive motors offer efficient easy pedalling support with Max torque levels of 40 or 50Nm. Bosch also have motor systems specifically designed for cargo bikes. These offer up to 85Nm or torque and are designed to carry heavy loads.
Mountain Bikes
The Bosch Performance Line crank drive motors are usually fitted to e-MTBs. The Performance Line CX motor is most popular and offers up to 85Nm torque. The Race version of this motor offers a sportier ride feel and is designed for those who want to ride as fast as possible. The Performance Line SL motor is their lightweight version which offers up to 55Nm of torque. This motor features Sprint mode that offers dynamic support at high cadences to help with steep climbs.
Shimano also produce a range of e-bike motors to suit different applications. Shimano motors tend to be a little smaller and lighter than others while offering comparable support levels. Shimano motors offer three support levels and motor performance characteristics can be fine-tuned in their app.
Some Shimano e-bike systems can be combined with Shimano electronic drivetrains to offer innovative functions that aren’t available on regular bikes. Free Shift allows you to change gear while you’re coasting while Auto Shift adapts intuitively to your pedalling input by changes gear automatically depending on your cadence.
City Bikes
Shimano’s E5000, E6000 and E7000 series motors, offering between 40Nm and 60Nm or torque, are fitted to city and trekking bikes. These offer intuitive support with plenty of power for riding on the road. Shimano’s Cargo bike motors are tuned to deliver more torque at lower speeds.
Mountain Bikes
Shimano’s flagship EP8 motor, offering up to 85Km of torque, is a popular ‘full power’ motor that’s found on many high end eMTBs. Weighing just 2.6kg it is also found on ‘lightweight’ eMTBs when detuned (usually to around 60Nm max torque) and combined with a smaller battery pack. The more affordable EP6 motor offers the same max torque but is larger and heavier than the EP8.
Specialized use their own motors on all their e-bikes. These are manufactured by German brand Brose who are well respected in the automotive industry and make e-bike motors for other brands. Software is equally as important as hardware when it comes to e-bikes, and it is here that Specialized excel.
Specialized e-bike motors are known for their smooth and intuitive power delivery over a wide cadence range. This means you don’t need to adapt your natural riding style to make the most of the pedal assist power as much as you do with some other motors. Gravel and eMTB displays are incorporated into the top tube while city bikes have a more traditional screen. The Specialized app offers useful customization options and features that enable the bike to manage battery capacity depending on how far or how long you want to ride.
Full Power
Specialized Turbo Full Power motors are fitted to all their e-bikes that don’t have an SL tag in the title. The Turbo 2.2 motors offer 90Nm max torque which makes it one of the most powerful. These are found on most or their mountain bikes. Trekking and city bikes feature lower powered versions that offer 50 – 70Nm max torque.
Lightweight
Weighing just 1.9kg the Specialized SL motor set a new e-bike benchmark. Offering 50Nm of torque in a lightweight package, e-bikes with these motors feel much more like regular bikes compared to their full powered counterparts. The original SL motor was quite noisy but newer versions are much easier on the ear.
SRAMs innovative Eagle Powertrain e-bike system combines motor and drivetrain into one interlinked package. The 90Nm motor is made by Brose and like Specialized it’s the software that sets it apart. Power delivery is intuitive, and the system is so neat that motor functions, gear changes and even dropper post actuation is done through the two wireless pods mounted on the handlebars.
The AXS eagle drivetrain offers immaculate shifting under power, and with the Powertrain system you can choose to shift while coasting or allow the bike to change gear for you using Auto Shift. There are just two power modes to choose from, but these are completely customizable within the SRAM app.
Giant’s SyncDrive motors are made in partnership with Yamaha. They have a variety of crank drive and hub drive motors suited to different cycling disciplines. Smart assist technology tailors support levels to both rider input and terrain feedback for smooth power delivery and intelligent battery management. Peak power for the SyncDrive motors varies from 20Nm for the hub drives up to 50Nm for the SyncDrive Life, 70Nm for the Sport and 85Nm for top-of-the-range the Pro motor. You can adjust support level and peak power individually for each for the four power modes using Giant’s RideControl App.
Full Power or Lightweight
Giant offer both full power and lightweight electric mountain bikes, but they approach this in a slightly different way to other brands. The SyncDrive Pro motor is compact and at 2.75kg relatively lightweight. Both their full power E+ and their lightweight E+ Elite bikes use this motor and rely on motor tuning and battery capacity to set them apart. At 400Wh battery capacity on the E+ Elite bikes is half that of the full power E+ bikes but you can still achieve decent range if you use the power modes carefully.
As well as working in partnership with Giant Yamaha make e-bike drive units for other brands like Haibike. The PW-X range offers 85Nm of peak torque and you’ll find this motor on premium bikes. The PW-S and PW-C series motors offer a max torque of 75Nm and 55Nm respectively. Each motor features three power modes, that you can cycle through manually as well as an auto mode that adjusts the power modes to suit rider input and terrain.
TQ are relative newcomers to the e-bike market but have been making electric motors for robots for decades. Weighing in at just 1.85kg the TQ-HPR50 is just about the smallest and lightest crank drive e-bike motor available and is a popular choice for SL eMTBs. It delivers up to 50Nm of torque and is exceptionally quiet thanks to the harmonic transmission design.
Fazua are another company that offer an innovative crank drive design that’s featured on many lightweight e-bikes. The cylindrical motor sits at 90° to the bottom bracket allowing for compact bike design. The drive unit completely disengages when not in use so there is no drag when riding above the 15.5Mph speed limit. There are currently two motors available offering 55 or 60Nm max torque. Both offer three power modes, and these are customizable within the Fazua app.
Hub Drive Motors
The Mahle eBikemotion motors are hub drive units with performance levels to rival lightweight crank drive motors but at a more affordable level. The X35 hub offers up to 40Nm or torque while the X20 gives you up to 60Nm. Both feature an understated control/display unit that makes use of a coloured LED ring to show support levels and remaining battery capacity. You have three support modes to choose from and you can cycle through these using the main display button or a handlebar mounted remote switch.
Other Hub Drive Motors
Other notable hub drive brands include Brompton. Their folding e-bikes use and efficient brushless hub drive motor in the front wheel. Combined with the easily removable battery pack this makes Brompton e-bikes lightweight enough to carry when folded.
