New PW-S2 Motor from Yamaha: Slim is Trendy

Normally, a trimmed-down version colloquially means a somewhat lower-performance version of a device. The new PW-S2 from Yamaha has indeed lost a lot of weight compared to its predecessor. At the same time, however, the mid-motor adds quite a bit of power.

The PW-S2 is smaller and lighter than its predecessor, the PW-ST. This is in line with the trend that other well-known motor manufacturers are also presenting. While the PW-ST weighed 3.4 kilograms, the new PW-S2 now is down to 2.85 kilograms. Yamaha’s top model, the PW-X3, has just 100 grams less.

Size compared between the Yamaha PW-S2 and Yamaha PW-ST

Versatile in use

In contrast, the increase in torque is somewhat more moderate. The former 70 Newton metres are now added to by five. With this performance, the PW-S2 strongly resembles the profile of the PW-ST. The manufacturer therefore expects that the new drive will be used in similar types of ebikes, as was the case with the previous model. Bike manufacturers liked to use it in ebikes for an urban environment, in trekking ebikes and in entry-level models in the mountain bike segment.

However, the real progress of the PW-S2 is less evident in these key figures than in its construction. For example, the ISIS bottom bracket shaft is 22.8 millimetres shorter than before. This leads to greater strength and promotes more efficient pedalling. This will have an effect on all four support levels when riding. Especially in automatic mode, Yamaha promises a “natural and pleasant riding experience”. At the same time, the shaft is long enough to also open up the option of fitting two chainrings on the crank.

More room for integration

Overall, the further development requires less space. The volume is said to have shrunk by as much as 20 percent. This should indeed be reflected in livelier riding dynamics. After all, higher torque meets less mass and a smaller volume. For bicycle manufacturers, this presumably also sounds very advantageous, as they can make their frames correspondingly slimmer and thus just as much lighter.

Pretty small for a big one: The Yamaha PW-S2 fits quite inconspicuously into the frame.

In addition to the attractive appearance, there are new options in terms of frame geometry and the corresponding riding behaviour. For example, shorter chain stays are possible. This is primarily important for e-mountain bikes, as it makes the frame more stable, ensures better contact with the ground and provides the bike with particularly high agility.

Immediately at full throttle

A feature that is already used on Yamaha’s PW-X3 aims in the same direction. It is a function called “Zero Cadence”. Ultimately, this is nothing more than an immediate start of motor assistance from the first time the crank is loaded. This is a great advantage, especially uphill, both off-road and on the road.

Yamaha PW-S2 motor at a glance:

• Type: mid-motor
• Rated voltage: 36 V
• Rated power: 250 W
• Max. assisted speed: 25 km/h
• Assistance modes: HIGH, STD, ECO, +ECO, OFF
• Max. torque: 75 Nm
• Weight: 2,85 kg

Pictures: Yamaha Motor Germany GmbH