E-BIKE BASICS
Get up to speed with the advantages – and disadvantages – of motor assistance
HOW DOES AN E-MTB WORK?
A ‘mid-drive’ motor connected to the cranks senses when you begin pedalling and kicks in to supplement your output. Power comes from a battery hidden in the down tube, and you can control the amount of assistance using a display and/or buttons mounted on the handlebar or integrated into the top tube.
Under UK law, e-bikes must have a maximum continuous (averaged-out over time) output of 250W and the assistance must cut out at 15.5mph. This ensures there’s a clear delineation between e-MTBs, which can legally be ridden anywhere a normal ‘pedal bike’ can, and electric motorbikes.
WHAT DIFFERENT TYPES ARE THERE?
Like MTBs in general, e-MTBs differ in terms of geometry, suspension travel, wheel size and parts fitted, with something to suit every riding style and most budgets. However, they can be divided into two main groups – ‘full-power’ and ‘SL’ (aka ‘lightweight’).
As the name suggests, full-power bikes supply maximum assistance to support your pedalling, courtesy of a motor with a peak output of 500W+ and at least 85Nm of torque. Many also come with a higher-capacity battery (600Wh+) to ensure a decent range. All this grunt does have its drawback, though, in the form of extra weight.
SL bikes have less torque (5060Nm) and, in many cases, a lighter, less powerful motor, combined with a smaller-capacity battery (320500Wh). The idea is that this gives a more natural ride feel and makes the bike easier to chuck around on the trail, especially when combined with lighter components. Many are compatible with optional range-extenders in case you want to do the odd longer ride.
WHAT ARE THE ADVANTAGES OVER A REGULAR MTB?
Pedalling assistance can help riders with injuries, disabilities or health problems get out on the trails, or less fit riders keep up with sportier friends/partners. Because they’re quicker up the climbs, e-MTBs also let you cover more ground in less time, which is great for getting in quick laps in-between work/family duties/etc, notching up plenty of descending or finishing long routes before darkness falls. They’re also a lot of fun to ride, and bring a whole new dimension to technical climbs.
WHAT ARE THE DISADVANTAGES?
The initial cost is high, and there are more things to go wrong down the line, from motor issues to battery degradation. They’re also heavy – with full-power bikes often weighing upwards of 25kg and even top-end SL bikes starting from around 16kg. If the motor and battery weight is low down and central in the frame, this doesn’t have too much of an effect on the handling, and can even aid grip and stability on descents. However, the extra heft is noticeable on flatter trails, when pushing uphill and when loading an e-bike into a vehicle – or if you crash and it lands on top of you!