Mahle has unveiled its first mid-mount motor system, the M40. Designed specifically for electric mountain bikes, and delivering 105Nm of torque and up to 850 watts peak power, the compact 2.5kg motor is one of the most powerful mid-drive systems available.
It offers up to 400 per cent pedal support even at high cadences, paired with new high-energy density batteries with up to 800Wh capacity – supporting as much as 2,500 meters of uplift on demanding trails.
Mahle is already a leading name in ebike motors, with its rear-hub systems powering electric bikes from more than 60 manufacturers worldwide. The M40 system combines sophisticated controllers and app-based customisation, with a total system weight of only 5kg.
Mahle’s product management lead, Gonzalo García, explains how the new M40 was developed and what it offers that’s new for the eMTB rider.
“Our DNA is light sports motor systems, but we wanted to develop a mid-drive system, so we can reach the mountain bike segment better. We started with the X35, X20 and X30 hub motors, top-performing systems for road, gravel and urban use. We’re applying the same Mahle DNA to the mid-platform.”
What makes the M40 different from the competition?
What sets the M40 apart from the competition, Mahle says, is its deep experience in developing lightweight, high-performance motors.
García explains that the M40 carries over the company’s signature lightness, weighing only 2.5kg, while delivering sporty power exactly when riders need it: “In combination with our batteries, you can build a bike that is very light at around 18kg.”
García emphasises that it’s not just about power, but the quality of its delivery too. With the M40 system, Mahle has refined both control and responsiveness.
Mahle aims to preserve a natural riding feel, one where “the bike looks like a bike”. This helps riders maintain control and confidence, especially those new to eMTBs.
“By customising the motor, you can have a bike that meets your own power delivery needs. That’s quite unique to Mahle,” García adds.
Industry-leading wheel speed detection
So how did Mahle develop the M40 motor and fine-tune its power delivery to achieve that natural feel?
According to García, the process began with extensive sensor data collection on prototype bikes. “We have a lot of sensors in the bike,” he explains.
“In our prototype bikes, we add even more sensors and record how the ebike performs in a lot of different events.
“For example, we’ll record what happens when tackling an obstacle and flag how the motor behaves, as well as capturing data from the rider, such as their power output.”
This data covers power, speed, terrain, and inputs from gyroscopes and accelerometers, all of which vary significantly between riding on flat ground and climbing steep trails.
A standout feature of the M40 system is its sophisticated wheel sensor, which records 84 data points per wheel revolution. García highlights the precision this provides: “That allows us to identify speed variation over less than 5 degrees of wheel rotation. That’s less than 3cm for a 27.5-inch wheel with a 2.5-inch tyre.”
By closely tracking the wheel’s movements, Mahle can understand how well the rear wheel is connected to the terrain, which directly influences traction and power delivery: “The motor is delivering its power to the rear wheel, so we can understand how the traction is being delivered and react in terms of output. We know what the rider is doing too and can adjust the motor behaviour to match.”
This level of detail exceeds that of many systems currently on the market, some of which may use only a handful of wheel sensor signals.
With such granular data on rider torque, power and speed, the system can even sense changes in terrain, such as when a rider is climbing or on flat ground. García explains: “We can even detect rocky sections, where the wheel won’t be moving stably and the suspension is working, as the speed data will be much more noisy.
“The rider’s pedalling torque will not be smooth, and they may need to stop pedalling to avoid hitting a pedal on a rock. We can use this to give them a little more overrun to pass the obstacle.”
This data feeds into the motor’s control algorithm, which determines when the motor cuts out – a legal requirement that must occur within two meters of the rider stopping pedalling.
García adds: “Depending on the speed, you’ll cover 2m in more or less time – faster on the flat than on a climb. Since you’re working against gravity, you’ll slow down more quickly on a climb too. So our power output and overrun will be different.”
Additional sensors, such as the gyroscope, help detect gradients and turns, enabling the system to avoid providing overrun when it’s unsafe, such as during cornering. Importantly – subject to OEM integration – the user can also customise these settings via an app, since “not everyone has the same skills and experience, and they need power delivery that’s safe for them”.
Mahle has also refined motor disengagement as the bike approaches the 25km/h cut-off speed. Instead of a sudden stop, the power gradually reduces, ensuring a smooth, natural feel rather than a jarring “wall” at the limit.
Automatic hill brake
There’s an automatic hill brake system built into the M40 too, which is activated based on the captured data rather than being button-operated, as with some competing systems.
“We are aiming for an instinctive ride and to be smart in fulfilling rider needs. We can detect that you’re on a steep climb, have zero speed, your wheel is turning back a small distance and you’re only providing a small amount of pedal torque,” explains García.
That’s input to the hill brake, ensuring that you don’t roll backwards and enabling you to start moving forward again, without putting a foot down and without rider input.
More novel functionality to come
Mahle will also carry over its heart rate detection from its hub motors. Pair the M40 with a heart rate monitor and, if your heart rate rises above predefined values you’ve set in the app, the motor will automatically increase the assistance level.
Other inputs, such as suspension data, are being explored as future parameters for the M40´s software, which will learn and adapt to how you ride.
A planned future upgrade will identify how you tackle an obstacle and apply the same output parameters next time it detects a similar condition.
“If you go over a root and always react similarly, the system knows the pattern and knows how you react. Then it can adapt when it detects the same conditions,” says García.
Mahle has a small number of launch partners for the M40 motor system, but expect to see more brands offering M40-powered eMTBs. It’s a motor system that looks destined to become as popular in the mountain bike segment as Mahle’s hub motors are for road, gravel and urban use.
