The motor fitted to an electric mountain bike can make a significant impact on how it rides and, with more motors and eMTBs available than ever in this burgeoning bike category, deciding on the best option can be bewildering.
In fact, ‘which electric mountain bike motor is best?’ is a question we get asked regularly at BikeRadar.
Of course, the answer isn’t clear-cut but, having headed up the new electric mountain bike category in our annual Bike of the Year test (dropping in May), I’ve been testing motors from all the leading brands.
This article will shed light on where each motor from the four main manufacturers (Bosch, Brose/Specialized, Shimano, Yamaha/Specialized) performs best – and where they falter.
There’s a lot to cover, so strap yourself in for the full deep-dive into electric mountain bike motors – or use the links below to skip to the sections you need. I’ve also included a glossary of the key eMTB motor terminology at the end of the article.
- What motor options are available?
- Specifications compared
- Performance – power
- Performance – control
- Performance – efficiency
- Performance – noise
- Performance – living with each motor
- Which eMTB motor is best?
- Glossary – eMTB motor terminology
Electric mountain bike motors – what options are there?
Full-fat electric bikes typically use a high-power motor with between 70Nm and 100Nm of torque and are powered by high-capacity batteries with from 504Wh to 1,000Wh of energy.
I’ve focused my test on the four motor brands typically specced on most full-fat electric mountain bikes: Shimano, Bosch, Brose and Yamaha.
First is the Shimano EP8 motor, officially the DU-EP800, fitted to a host of bikes from brands including Santa Cruz, Yeti, Marin, YT Industries and Nukeproof.
Next is Bosch’s Performance Line CX, fitted to bikes from the likes of Mondraker, Trek, Whyte and Scott.
Then there’s Brose’s Drive S Mag, also known as Specialized’s Turbo Full Power System 2.2 Motor. This system is fitted to Specialized’s most powerful ebikes, as well as models from German brand Rotwild and Spanish brand BH Bikes.
Finally, we’ve got the Giant and Yamaha-developed SyncDrive Pro, also known as the PW-X3. Most commonly fitted to Giant bikes, it’s also available on some Haibike and Raymon models.
While I’ll focus on these models, this isn’t an exhaustive list of ebike motors.
A number of lightweight options exist, found on bikes where, unsurprisingly, there’s more focus on reducing weight, and less on all-out electric grunt.
Lightweight ebikes use smaller, less powerful motors delivering as little as 30Nm of torque but up to 60Nm. They’re usually fitted with lower-capacity batteries that are generally smaller than 500Wh. Bike weights are typically between 13.5kg and 20kg depending on exact specifications.
Here, Fazua’s modular Evation motor, fitted to bikes from Kinesis and Lapierre, goes head-to-head with Specialized’s Mahle-made SL motor, found on the American brand’s Turbo Kenevo SL and Turbo Levo SL bikes.
Canadian brand Rocky Mountain’s ebikes are fitted with a full-fat motor called the Dyname drive system, available exclusively on Rocky bikes.
Panasonic also makes motors, and there’s Shimano’s de-tuned EP8 RS found on the Orbea Rise to consider. There are a host of rear-hub motors, too, but these are less relevant for mountain bikes, and are more commonly found on electric road bikes or electric hybrid bikes.
Again, to avoid over complication, I’ve compared the four most common motors you’re most likely to encounter when considering an eMTB purchase.
Electric mountain bike motor specifications compared
Comparing the headline figures from each of the motors in this test is a good way to initially understand how they could feel out on the trail in any given scenario.
|Bosch Performance Line CX||Brose/Specialized Drive S Mag/Turbo Full Power System 2.2||Shimano EP8||Yamaha/Giant PW-X3/SyncDrive Pro|
|Support||340 per cent||410 per cent||400 per cent||400 per cent|
|Battery capacity||Up to 1,250Wh||Up to 700Wh||Up to 900Wh||Up to 750Wh|
|Waterproofing||IP56||IP56||Self-certified 'fully waterproof'||Undisclosed|
|Smartphone app||Bosch Flow||Specialized Mission Control||Shimano E-Tube Project||Giant RideControl|
Torque, power and assistance
Higher torque and watt figures, or maximum support percentage, should equate to a more powerful-feeling motor, helping riders ascend quicker or with less effort.
Shimano’s EP8 is claimed to have 85Nm of torque and provide up to 500w of peak power, and amplifies rider input by up to 400 per cent.
Bosch’s Performance Line CX equals Shimano’s torque, also delivering 85Nm, but only offers 340 per cent support. Bosch wasn’t able to disclose the Performance Line CX’s peak power.
The Yamaha/Giant PW-X3/SyncDrive Pro also has 85Nm of torque, matching Shimano’s support ratio at 400 per cent. Continuous power is rated 250w – the maximum allowed under ebike laws – but Giant doesn’t quote peak power figures.
The Brose/Specialized Drive S Mag/Turbo Full Power System 2.2 Motor boasts 90Nm of torque, beating – on paper – the other motors on test. It’s also claimed to offer 410 per cent assistance and 565w of peak power.
If this were just a game of Top Trumps number crunching, the Brose would come out on top. But, as we’ll find out, it’s not as simple as comparing the numbers on a spec sheet.
What modes do each of the motors have?
Each of the motors have pre-programmed modes that the user can switch between when riding. The modes deliver different levels of assistance, usually from low to high.
Shimano’s EP8 has three riding modes: eco, trail and boost, plus a walk mode.
Bosch’s Performance Line CX motor has four stock modes, but depending on which control unit is fitted, the trail mode functions differently. For Purion-equipped bikes it has eco, trail, eMTB and turbo. Kiox 300 bikes have eco, trail+, eMTB and turbo.
Bosch’s eMTB and trail+ modes are reactive to rider input, where torque and power assistance levels are altered on the fly depending on how hard a rider is pedalling.
Specialized bikes have three stock modes – once again eco, trail and turbo – but if the bike is fitted with the MasterMind TCU control unit, it’s possible to change assistance levels in 10 per cent increments rather than switching between three predefined modes.
Finally, the Giant motor has five modes: eco, tour, active, sport and power. The active mode functions similarly to Bosch’s trail+ and eMTB modes, where increased rider input increases the amount of motor assistance.
Battery capacity and run times
Claimed run times can vary greatly and are dictated by a huge number of factors – not only which assistance level is selected or how much capacity a battery has.
Bike and rider weight, tyre compound and pressure, the weather conditions, trail type and smoothness, and how hard a rider is pedalling all influence how long an ebike’s battery can last.
That said, battery capacity is a good general indicator, where larger-capacity batteries will generally provide more range.
The Bosch motor is only compatible with Bosch batteries. The range starts with a 300Wh unit and increases to the headlining 1,250Wh battery. This makes it one of the biggest-capacity batteries.
Unlike Bosch, Shimano’s EP8 motor can be paired with third-party batteries. Shimano has its own 504Wh and 630Wh units, too. SL ebikes such as the Orbea Rise use a 360Wh unit, while Norco’s Range VLT with EP8 motor can be paired with a 900Wh battery capacity.
Meanwhile, Canyon has developed its own 720Wh and 900Wh batteries for use with the EP8 motor on the new Canyon Spectral:On.
Giant’s SyncDrive Pro motor features 625Wh and 750Wh battery capacities, but the Yamaha-branded version of the motor maxes out with a 600Wh capacity.
Specialized’s 2.2 motor is fitted with up to 700Wh capacity batteries, but the Brose version maxes out with a 630Wh unit.
The limiting factor for battery capacity is figuring out how to improve energy densities, where the aim is to fit the more potential energy into the same space without increasing battery size and weight.
Ever-advancing technology means ebike motors are decreasing in size and weight while offering more power and torque. This is a great thing for riders who are beginning to get the advantages of more power without significant weight penalties.
For our motors, the Shimano EP8 is the lightest, weighing a claimed 2,600g.
Next is the Giant/Yamaha motor, tipping the scales at a claimed 2,750g.
This is swiftly followed by the Specialized/Brose unit, weighing a claimed 2,900g.
Finally, Bosch’s Performance Line CX matches the Brose, also weighing a claimed 2,900g.
Given batteries can weigh from 3,150g (Shimano BT-E8035) up to 4,500g (Norco VLT 900Wh) depending on their capacity, the relatively small difference in weight between the Shimano and Bosch motors isn’t a particularly significant factor.