A quick guide to electric mountain bikes

What you need to know about e-MTBs

The bike industry is pushing e-MTBs hard. Why? Simple. It’s because they open up the sport to a whole new market of riders who are too out-of-shape or injured (or just plain lazy) to use a conventional mountain bike. 

And – shh, don’t tell anyone! – they can actually make pretty fun additional bikes for existing riders, too, letting you cover more ground, more quickly. Wherever you stand in the great e-bike debate, it pays to be informed. 

So whether you think e-MTBs are marketing fodder, a genuine revelation or you just don’t know, read on to find out more...

Power to the pedals

Hub motors are common on cheap e-bikes but most e-MTBs use ‘mid drive’ systems located near the bottom bracket, generally made by Bosch, Yamaha or – with the recent launch of the STEPS MTB systemShimano

Shimano's STEPS components
Shimano's STEPS components

Most e-MTBs are classified as pedal-assist, meaning the power only kicks in when you pedal. This type of bike is commonly referred to as a ‘pedelec’. Some have a throttle instead, where a push of a button propels you forward, whether or not you’re pedalling. This makes them closer to an electric motorbike, but with a much lower top speed. A few feature a combination of pedal assistance and throttle. 

It’s pedelecs we’re going to focus on in this article. They may still have to be pedalled, but good ones will provide enough help to let you spin breezily up steep climbs that were once a wheezing, lung-busting chore, letting you chase your mates witha grin on your face.

Turbo boost

The amount of power supplied by the motor is controlled, on most bikes, with a switch near one of the grips and often also on the computer mounted centrally on the handlebar. Most e-bike makers recommend starting on a lower setting, as the initial thrust on high power can be startling. 

Once up to speed, you can fine-tune the amount of assistance you’re receiving from the motor, from zero up to full power, which is usually 200w to 350w. For reference, 250w is a power level that an experienced recreational cyclist could ride at for more than an hour, while 350w for an extended period is professional level.

Deciding whether you want to be in ‘turbo’ or ‘eco mode’ doesn’t seem like a hard choice – as Jeremy Clarkson would say, “more power!” But it’s not always that simple. The higher the power setting, the shorter the range. Most pedal-assist bikes will show you the remaining battery life and an estimated mileage range, and some will adjust this range based on what power setting you select. 

In reality, there’s an element of misunderstanding about e-bikes

Achievable distances on a single charge can range from 15 miles on the highest assistance setting when going uphill to a claimed 127 miles for a particular Kalkhoff model in economy mode. In most settings, you can expect 20 to 40 miles before you have to recharge the battery.

Know your rights

According to GOV.UK, to be used legally on UK roads (and chances are that if you have an e-MTB, you'll want to use these to get to the trails), an e-bike’s motor must have a maximum power output of 250w and it must cut out once the bike reaches 15.5mph. This limits the appeal of throttle-assisted bikes in particular, which technically also have to be granted a certificate of conformity to be used in the UK. The plus side is that when an e-bike is limited in this way, you don’t need a licence or insurance.

Faster and more powerful e-MTBs are available, and you can also chip or tune some motors, but these can only be used off-road and on private land. In Switzerland you can get a licence for a 28mph e-bike, but there’s no sign of British law changing any time soon.

In the US, laws vary by state.

An e-MTB can take you further than you might manage on your own
An e-MTB can take you further than you might manage on your own

The weakest link

With the added power created by the electric motor, drivetrain wear is increased on e-bikes. The temptation to hammer through the gears as your speed soars is hard to resist! Chains, mechs and cassettes all take a hammering much quicker than on conventional bikes – though some brands are reacting to this (see opposite).

If your e-bike’s electronics stop working, you’ll need a computer technician, not a bike mechanic, to fix it. And then there’s the battery. Think about how quickly your smartphone drains after a year or two of regular charging. As e-bikes get older their lithium-ion cells lose charge capacity and their range suffers. You can buy replacement batteries but they cost hundreds of pounds.

Component e-volution

Until now e-bikes have been reliant on conventional stop-and-go equipment that simply wasn’t designed to take the load of your muscles and a motor. Add in last minute, clunking shifts and gear ranges chosen to nurse human horsepower and it’s no wonder both Shimano and SRAM have developed e-bike specific components ready for next year.

Shimano’s Total Electric Power System (STEPS) comes in a leisure version and the more torquey (70nm to be precise), higher capacity, 500Wh battery E8000 MTB version. It comes with a full-size chainring on hollow or solid cranks rather than the tiny 14t cogs of Bosch and other systems. Shimano expects it to be teamed with conventional gears and hasn't offered specific brakes or cassette ratios yet, either.

In contrast, SRAM’s EX1 groupset includes cranks and is designed to work with other brands’ motor/battery units. A wide-range (11-48t), eight-speed ‘E-BLOCK’ cassette suits the faster acceleration of e-bikes while reducing wear from double shifting and extreme chain lines. The group also teams SRAM’s Guide lever with their old Code DH calliper to create the extra-powerful Guide RE for stopping the extra mass of electric bikes.

SRAM's EX1 drivetrain
SRAM's EX1 drivetrain

Can of worms

While e-MTBs have quickly gained a lot of ground in mainland Europe, they’re causing a bit of a hoo-hah in the UK and USA. In the States, the main issue is land access. US mountain bikers have fought tooth and nail to be allowed access to a limited number of trails and they’re worried e-biking will upset the already fraught relationship with landowners. 

The doomsayers say e-bikes will prove monstrously destructive, churning up delicate trails and leaving rear-wheel ruts deeper than those seen at motocross races. While electric-assist bikes may be heavier than regular MTBs and more likely to be ridden by unskilled riders, the restrictions on speed and power make this seem unlikely. 

They’re no faster on the descents (in fact the motor, battery and associated electrical gubbins make them heavier and less manoeuvrable) and although they’re a lot quicker on the climbs, it’s easier to stop and slow down there, thanks to, you know, gravity.

In the UK, the main argument seems to be that it’s “not real bike riding” when you’re not travelling fully under your own steam. E-bikes with throttles certainly blur the lines between motorbike and mountain bike. But if they help people who are injured, disabled or just unfit into biking, and open up the wilds for people to enjoy surely that's a positive? And why does using a motor to get to the top give any less ‘pure’ an experience than jumping in an uplift truck?

In reality, there’s an element of misunderstanding about e-bikes. They’re not the dirt eating, rut making monsters that they’re sometimes portrayed as. They’ll do the same amount of ‘damage’ to most trails as a regular mountain bike. 

Sure, it may be annoying when an e-biker sails past you on a climb, but think how much fitter you’re getting! Why hate?

The future of e-MTBs?

A shift to state-of-the-art handling and suspension performance has begun that’ll make e-MTBs a much more tempting flat out, full gas option at the top of the price range. But few people can afford to spend £7,000 to £10,000 on a flagship bike. What’ll really make the difference is technology trickling down to more affordable ranges, as well as the inevitable improvements in motor and battery performance as this category comes of age.

The e-MTB market at the moment all seems to be one big shouting match, with everyone yelling about how much power they’ve got, how much torque, how fast, how far – yadda, yadda, yadda. But Focus has gone down a different route with its Project Y prototype. Based around its flyweight Raven XC hardtail, not only does it look much like a regular mountain bike but it weighs just 13kg. 

That’s lighter than many trail bikes, yet it packs a punch, with the motor offering 250w of assistance. There’s a compromise or two to be made, of course – the battery will only last for around 18km and you’ll be riding on semi-slicks. While the Project Y bike may not break sales records if and when it goes into production, it does point to a different future for e-bikes – one where their weight, look and ride feel is much more like a normal bike.

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