This year marks 30 years since Yamaha Motor launched the "world's first electrically power-assisted bicycle." The company celebrated in style last month with the launch of a special-edition YDX-Moro 07 eMTB, and is now keeping the party going with its lightest drive unit.
We offered an abridged history of Yamaha's ebike journey in our coverage of the special anniversary model, but to quickly summarize – after starting with bikes rocking gas engines in the 1970s, engineers took advantage of advances in electronics to prototype an electric pedal-assist model in the late 80s.
Three years later, a production version featuring a 235-W motor, torque sensing and a 12.5-mile battery went into limited production across a few prefectures in Japan before going nationwide the following year. Yamaha officially entered the US market in 2018, and has been pumping out impressive builds ever since. They're not exactly budget-friendly, but they are reliable and built to last.
The flagship PW-XM drive unit is reported to be the lightest in the pack, tipping the scales at 2.6 kg (5.7 lb) thanks to magnesium housing designed especially for this unit, and leveraging the company's manufacturing know-how from the production of the R1M Supersport motorcycle. The liberal use of magnesium also allowed for improvements in heat dissipation to be made for cooler running.
The 250-W motor is said to have the highest torque-to-weight ratio in the whole range, can produce 85 Nm (62.6 lb.ft) of torque "even when under high loads for long periods" and is reckoned the perfect fit for premium eMTB applications.
An auto assist mode allows riders to focus on the trail and not have to worry about manual switching between the five available power modes. Zero Cadence Technology powered by a proprietary sensor system provides instant torque for a responsive ride up to 25-km/h (15.5-mph). And the new drive can also play nice with any of Yamaha's existing displays and batteries.
Ebike manufacturers using chassis designs built for Yamaha PW-X3 and PWseries S2 drives now have a third option, as the new PW-XM is fully compatible with the motor brackets on such frames.
The PW-XM eMTB drive is available to ebike builders now, so we should start seeing the first in the wild soon. Pricing information has not been revealed.
Source: Yamaha