At the core of e-MTB technology is the mid-drive motor.
Neatly packaged into your e-MTB’s bottom bracket, these compact electric drive motors are elegantly engineered to be unobtrusive, powerful and reliable.
As power is released from the battery pack residing in your e-MTB’s downtube, it allows the mid-drive motor to spin and surge additional torque into your pedal stroke.
With e-MTBs surging in popularity, there are now more mid-drive motors than ever before. Here we keep you up to date on the latest technology, and which is best.
- Best e-MTB: our pick of the best e-mountain bikes available this year
- Best budget e-MTBs: great e-mountain bikes that won't break the bank
The best e-MTB motors
Shimano’s conservative product development strategy has often befuddled followers of the Japanese component brand.
But for those who have the required patience, Shimano’s greatest advance is the new EP8 mid-drive motor. Reacting to the trend of riders wanting lighter e-MTBs, the EP8 can be powered with a variety of battery packs. It is also wonderfully compact and light.
Showing awareness of the possible heat build-up issues that can influence an e-MTB when used at peak assistance in sweltering conditions, the EP8 has a casing with cooling fins.
Shimano’s drivetrain design experience shows in the standards this new EP8 mid-drive motor adheres to. It spaces custom cranks at a 177mm Q-factor, with available arm lengths of 160mm, 165mm, 170mm and 175mm. Shimano is one of the very few mid-drive motor suppliers capable of offering an ultra-short 160mm crank.
Software and adaptability make the EP8 intuitive to use, with the motor’s output characteristics adjustable on the move thanks to Shimano’s SC-EM800 computer. There is also a terrifically clever ‘Walk Assist’ mode. If you are pushing up severely technical terrain, the EP8 motor will provide 2.5mph of rolling assistance.
Shimano's display screen and handlebar controls are also noticeably refined with an unobtrusive setup that offers easy use whilst also remaining tucked away to avoid damage.
Bosch is a huge engineering conglomerate, and its cycling division has not been shy of deploying resources into the e-MTB space.
The company’s latest Line CX mid-drive motor is potent and sophisticated. With a peak torque output of 85Nm, it will effortlessly assist you up the steepest climbs.
All that pedal-assistance is of no use if it cannot be meticulously modulated. To ensure the Line CX unit is always assisting, there is a highly-sensitive sensor configuration. Capable of 1,000 data measurements per second, and with its output harmonized by a 32-bit microprocessor, the Bosch Line CX drive unit delivers a predictably linear response.
Bosch’s engineers and software programmers have done especially well calibrating the Line CX’s high cadence responses when climbing over technical terrain in the lowest gears.
Yamaha has an enviable background in motorcycle design, and the Japanese company now offers an updated e-MTB motor.
Although the PW-X2 mid-drive system isn’t light at 3,060g, it delivers a generous helping of pedal assistance. When running at its 80Nm peak torque output, the PW-X2 motor offers a 360 per cent ratio of rider input to actual drivetrain torque.
Yamaha offers a choice of three energy sources for its PW-X2 system, depending on your range requirements. The available battery sizes are 400Wh, 500Wh and 600Wh. Range extenders are the latest innovation amongst second-generation e-MTB systems, and Yamaha offers 250Wh and 500Wh plug-in power packs for the PW-X2.
If you enjoy the technical climbing sections that an e-MTB is capable of clearing, Yamaha’s PW-X2 is a great choice. It has an abundance of power even at low cadence and relatively predictable linearity in its torque delivery.
The sheer scale of Giant’s business has allowed the Taiwanese cycling brand to invest in its own mid-drive motor technology.
Working with Yamaha, it has produced the SyncDrive range, with its Pro model representing the peak of current Giant e-MTB development.
A six-sensor system interprets your requirement for pedal-assistance and delivers 80Nm of torque, as required. The multiplication factor of Giant’s SyncDrive Pro mid-drive motor varies from 50 to 360 per cent of rider input.
Capable of syncing up to 170rpm of cadence, this Giant e-MTB motor facilitates five modes of assistance. The ability to deliver 360 per cent of power at such a high cadence is crucial when climbing really steep gradients.
Thanks to meticulously programmed mechatronic software and a wonderfully comprehensive sensor system, Giant’s SyncDrive Pro gives you all the pedal-assist power, with none of the unnatural e-MTB ride characteristics.
Fazua’s engineers understand that even when riding e-MTBs, weight is everything. The German company’s modular Evation mid-drive motor is incredibly light and compact.
At only 1,920g, it is nearly half the mass of some rivals. Fazua has sacrificed some peak power in the pursuit of low mass (the Evation delivers only 55Nm of torque), but it is targeted at a specific rider.
Whereas traditional e-MTBs require a surplus of battery capacity and mid-drive motor output to assist riders with a relatively low fitness threshold up steep inclines, the Evation wants to enable the intermediate mountain biker.
If you possess the requisite fitness but lack the time for a three-hour ride, this is the mid-drive motor for you. With its low weight and adequate assistance, it helps to integrate multiple climbs and descents into a shorter overall riding schedule.
Dual-sided torque sensors enable the Evation to deliver a very natural pedal-assistance function.
Specialized has been a spirited early adopter of all things e-MTB. The Californian company’s Levo platform can claim to have shown what is possible with a dedicated e-MTB platform.
From its engineering facility in Switzerland, the Specialized’s e-MTB product team is continuously seeking better performance. Comprehensive rider research showed Specialized that its Levo customers were not always using the full battery or motor capacity.
This knowledge created the opportunity for SL 1.1, a much lighter e-MTB motor. For those who are adequately fit, but use an e-MTB as a tool to ride more terrain in a shorter time, the SL 1.1 is ideal.
Limited to 20mph of peak speed assistance, the SL 1.1 mid-drive motor effectively doubles rider input. For those who are adequately fit, but use an e-MTB as a tool to ride more terrain in a shorter time, the SL 1.1 is ideal.
Due to its lower power rating, the SL 1.1 mid-drive motor retains impressive endurance. Drawing energy from a 320Wh battery pack, it will help you along for five hours of riding.
If all you seek is power, then look no further than this German mid-drive motor. Although TQ has been producing mid-drive motors for many years, mountain bikers only became aware of the company’s potential, thanks to Haibike.
When Haibike integrated the HP120S into an e-MTB concept, everyone had to take notice. With 120Nm of peak torque delivery, this is the most potent pedal assistance you can buy. None of the TQ’s rivals can match it for sheer climbing performance.
This mid-drive motor is quite capable of keeping its 15mph assistance threshold up the steepest of inclines. In fact, the HP120S is so powerful, that inexperienced riders, can quite easily accidentally provoke it into an aggressive wheelie.
The TQ motor might be heavy, at 3,900g, and boldly finished, but if you desire sheer power and climbing speed above all else, this is the best e-MTB mid-drive motor option. All that performance needs to be powered by a relatively large battery pack, with a recommended minimum capacity of 630Wh.
To deliver significant range over varying topography, you will probably need to pair the TQ120S motor with a 1,000Wh battery pack, and that means a notable increase in weight.
One of the most exciting aspects of e-MTB development has been the diversity of new suppliers. Companies that are familiar to mountain bikers in other parts of their lives are now present on their e-MTBs.
Panasonic, the Japanese electronics specialist, has a compact mid-drive e-MTB motor. It is branded as the GXO and has an incredible power-to-weight ratio. Panasonic understands that mass is a crucial issue for mountain bikers, and engineers at the company attempted to make its GXO light but powerful.
There is no arguing with this mid-drive motor’s headline statistics. It produces 90Nm of torque at a total mass of 2,900g. Rider input pedal assistance calculates to a threshold of 300 per cent, which should guide you up the steepest of climbs.
Panasonic's experience in the digital camera market, where it has been producing lithium-ion battery cells for many years, serves the GXO’s purpose well. There are two battery packs for this mid-drive motor, both of Panasonic’s own design: a lightweight 288Wh and a more energy-dense 433Wh configuration.
As a supplier of choice for Tesla’s electric vehicles, Panasonic has some of the best battery technology and cell durability in the world. The GXO’s battery packs should provide excellent durability even after the most intense use.
How to choose the best eMTB mid-drive motor
As a vanguard technology, the mid-drive motor is rapidly evolving. Different engineering teams are all refining their interpretation of the concept.
The decision points should mostly be about the quality of your mid-drive motor’s pedal-assistance and its endurance. Better efficiency allows for a smaller motor and battery pack, which reduces weight, giving you a lighter, more agile e-MTB to ride. One that will feel closer to a conventional mountain bike.
If you don’t require peak pedal-assistance all of the time, one of the lower output mid-drive motors will be entirely adequate. They might only have half the power of a ‘standard’ e-MTB system, but the weight saving is substantial.
Selecting your e-MTB mid-drive motor for its power and potential battery endurance, is easy: you simply evaluate the power output and available battery capacity options.
Where the e-MTB experience, in terms of mid-drive motor choice, becomes more complex is the overall riding characteristics. In slow, steep and technical terrain, mid-drive motors can be tricky. A power surge in one of your climbing gears, at high-cadence, can easily lift a front wheel and unbalance you.
Engineers have recognized the specific challenge of e-MTBs being ridden very slowly, up steep and uneven terrain, and are now deploying more sophisticated control software and sensors. The combination of improved mechatronics on most second-generation mid-drive motors delivers more predictable pedaling-assistance when climbing.
It is worth remembering that the appeal of a large power rating must be considered against the reality of having to ride along with an equally large battery pack to keep it powered.