DJI, Bosch and Specialized have dominated the e-bike headlines in the past 12 months, with each brand releasing high power motors pumping out more than 100Nm of torque. Well now there’s a new one joining the exclusive ‘100 club’: German brand Mahle has just released its M40 motor… and it has one of the best power to weight ratios out there.

With 850W of peak power and 105Nm of torque, the new M40 is punchier than the Bosch CX Gen 5 even after its update this spring, and packs in more power than even the new Specialized S-Works with 720W. What’s more, the Mahle M40 has a claimed weight of just 2.5kg, 500g less than the Specialized 3.1 Brose unit, and 200g lighter than Bosch CX. That’s 340 watts per kilo then the second best power to weight ratio out there.

And I’m sure you all know which motor is top of the pile (or should that be mountain), yup it’s the DJI Avinox motor, at a massive 400 watts per kilo thanks to its 1,000W output and 2.5kg claimed weight.

Forget the power for a minute, the Mahle M40 has got to be the best looking motor out there, with a subtle matt black finish

Mahle M40 need to know

• New high e-bike power motor with 850W power and 105Nm of torque
• Motor weighs 2.5kg, matching that of the DJI Avinox
• Two batteries, a 534Wh option and 800Wh, both at 48volts
• Traction control thanks to precise speed sensor measuring every 5°
• Not available yet in the UK… boo!

The Mahle sensor delivers more data to the motor’s software than conventional speed sensors, and this lets it taper the power when it senses the wheel is slipping

Traction control

Mahle has been making e-bike motors for decades now, but it’s been putting them into hubs for commuter bikes. This is the first proper mountain bike motor for the German brand then, and it looks like the M40’s got more than just raw power in its arsenal too, with a sensor capable of measuring a bike’s speed every 3cm. So while almost every e-bike out there does this every rotation of the wheel, the M40 can measure it 84 times over a single rotation, or every 5 degrees. And yes, before you say it, the DJI does this too.

How useful really is this data though? Extremely useful, if the Amflow PL Carbon e-bike is anything to go by. When we reviewed the bike it wasn’t actually the big power that wowed us most, more the control the Avinox system gives to the rear wheel, working like traction control to prevent us spinning out on the climbs. Mahle has the same thing going on, with a ring mounted to the brake rotor.

The Amflow is a beast on the climbs thanks to its mad power and its control too

“The M40’s adaptive motor response delivers a traction control-like effect,” Alberto Serrano Álvarez told me. “Thanks to its precise sensor suite, the system continuously monitors rear wheel speed, terrain feedback, cadence changes, and instant torque input.”

“When reduced grip or unstable conditions are detected, for example, during rocky climbs or when the wheel begins to slip, the motor dynamically adjusts power output in real time to help maintain traction and control.”

With great power comes great responsibilty to leave the trails rut free

Now that either sounds like some sort of AI nightmare to you, or the best thing since sliced bread. For me it’s an amazing development, techie climbing is more of a chore than a fun challenge and I appreciate all the help I can get.

Mahle M40 batteries

I was worried for Mahle when I saw it had developed a 534Wh battery called the iM5, way less than the current standards set by other brands. Fortunately it had the good sense to build an 800Wh version too, called the iM8, which it reckons will climb 2,500m and cover 150km. That sounds overly optimistic for UK riding, but those kinds of figures are always very subjective.

A choice of batteries means brands could potentially build an SL bike from the M40

Don’t write off the 534Wh battery just yet though, it’s possible brands will use to to develop new SL e-bikes, give the motor and the battery’s weight. We’re talking about a combined motor and iM5 battery weight of just 5kg – Fazua’s Ride 60 setup is just 4.2kg but gets 100Wh less juice.

For reference, the bigger battery weighs around 3.75kg, the same as DJI’s and meaning it has one of the best power to weight ratios of any battery.

Both sized batteries are interchangeable through a dealer, and Mahle says they’re “fast charging” too, but at 3 hours to 80% on the smaller version and 4.5 hours on the 800wh, it looks pretty pedestrian to me.

Colour top tube display is a welcome touch

Display and power modes

The Mahle Head Unit+ is a 1.9in colour screen, it’s customisable so you can see the usual gamut of information that most of us pretty much ignore. I don’t think it’s touch screen though, unlike the Avinox display. That’s blacked up by Mahle’s Trio Remote, a wireless, compact control unit on the bars to let you switch between power modes.

Mahle also says it developed an autohold for its new M40, called Hill Brake it’s there to make pushing up a little easier. The three power modes are snappily called Level 1, Level 2 and Level 3.

How tactile does this bar remote look?

M40 technical jargon

The M40 is housed in a magnesium and will generate a Q-factor of 179 mm, a couple of millimetres narrower than the likes of Bosch and Specialized. Mahle says its compatible with standard ETOR cranksets, allowing integration with a wide variety of crank references already available on the market.

“The chain interface is also designed to support not only high-end aluminum components, but also the new generation of more affordable and durable drivetrain systems. This ensures flexibility for OEMs and helps reduce overall bike cost compared to other systems,” Alberto told me,

“Importantly, there is no need for an external power meter. The M40 includes a fully integrated torque sensor within the motor axle, enabling real-time rider input detection without the need for additional components.”

Head to France and try the new Labyrinth (then tell us all about it!)

Where can I ride a Mahle M40?

There are five launch partners for the motor, and none of them have distribution in the UK. Which is a real shame. Abums, Labyrinth, Messingschlager, Sants, and Titan Racing are all selling bikes with the M40, meaning Labyrinth out of France is your best chance of trying the new motor if you’re using based.

And you thought the M40 was just for cars

We’re expecting new brands to be coming on board Mahle soon though, Mahle said, offering both SL e-bikes and full power. It’s also said the M40 is just the beginning for its e-bike motors, with “the M Series platform, mid-drive unit based… enlarged in the upcoming years.”