Trek has revealed its new Powerfly FS electric mountain bike, and in doing so, joined the fray of off-road capable, electrically-assisted machinery.
The Powerfly FS uses a Bosch pedal assist system, paired to a 120mm travel, 27.5in-wheeled frame. The Powerfly will be offered in full suspension and hardtail versions, as well as in women's-specific models. Where the Powerfly differs from other full suspension e-bikes is that the motor has a custom mount and case, which allow the use of shorter chainstays and a lower shock mounting. This gives what Trek believes is class-leading handling.
While mountain bikers in the UK and US tend to be dismissive of e-bikes, enthusiasm in Europe is definitely building. Because of this, the Powerfly FS was developed by Trek's European office, which is more familiar with this sector. But, as John Riley, Trek's MTB Product Manager, said: “Making a bike like this isn't as easy as just taking a mountain bike and putting a motor on it.” Trek states the Powerfly will not be available in North America.
Trek's engineers have used the spare space in the standard casing to put their pivot closer to and slightly above the chainline, to give less squat under power. It also means they could give the Powerfly FS shorter chainstays than its rivals, a common complaint around the handling of such machines. It also means that the engineers could put the shock mount lower, in order to give an improved suspension kinematic that is better suited to the constant power delivery that electric assistance offers – compared to the 'lumpy' delivery of flesh-based propulsion.
The bike is fitted with a specially-tuned RockShox Monarch shock, with lighter low-speed compression damping. This aims to give a ride that's better suited to the requirements of an e-bike. It also means that standover is increased and that the bulk of motor, shock and battery is kept lower, inspiring greater confidence in riders who may be newer to the world of riding off-road.
Frame stiffness was a big issue, so the bike is built tough, using the same size pivots as the longer-travel Remedy
The Powerfly FS is available in five different frame sizes, from 15.5in to 21.5in. The 'Balanced Geometry' is broadly similar to Trek's standard off-road range, but higher front ends aim to give a ride feel that's less intimidating than more enthusiast-focused machines.
The custom case features an in-built chain device and, in what might be a nod to the more casual market, a bottle opener. Trek has also developed its own Motor Armour, which helps protect the sump of the bike. More importantly, the design means that it can use a smaller 15T drive sprocket without chain retention issues, instead of the narrow/wide tooth profiles of their rivals, which are limited to even numbers. With a drive ratio that gears up by 2.5, this is important in ensuring the gearing still works on steep climbs.
While the subject of off-road e-bikes is still anaethema to many, the time and effort that Trek has put into this bike – and the market – shows that they're only going to become a more common sight on trails as time goes by.
A 25-mile test loop with serious climbing showed the potential of the bike and system