The mechanics of mountain bikes

The incredible tech powering your off-road adventures

Bicycles are remarkably efficient modes of transport. Just look at a typical car, which converts petrol into motion via combustion: only around 20 to 25 per cent of that fuel will be transformed into useful kinetic energy, while the rest ends up as waste heat and pollutants. Compare that to the 90 per cent efficiency that a typical bike derives from the driving force of your legs. But just like motorised vehicles, a bike specialised for a Tour De France-style road race or cruising along a flat promenade, will be very different from those designed for a rough, off-road track.


The specialised components allow a mountain bike to go where no other bike dares

The rigours of off-roading – which include uneven terrain, wet and slippery mud and wild inclines – mean that mountain bikes need to be much more robust than other types of bike. It’s easy to spot the differences when a mountain bike and a road bike, for example, are side by side. Mountain bikes will have much wider tyres – three or four times the width of a road bike – with a more pronounced grip. The bike will feature front and sometimes rear suspension, often twice the number of gears, a thicker frame and a disc brake system. Even a bad cyclist on a road bike could outpace a person riding a mountain bike on flat, even terrain because road bikes are so much lighter and their tyres are smoother. But in unforgiving, off-road conditions, a mountain bike is in its element.


Mountain bikes typically have 21, 24 or 27 gears, compared to the 11 of a road bike

Gear up to go

The pace at which you can turn the pedals will be dictated by the incline your bike is on. Obviously, this is going to be a lot more difficult cycling uphill than on a flat surface, so mountain bikes incorporate a number of different-sized sprockets – or cogs – to produce a gear ratio that will allow you to ride more comfortably. A 27-speed gearing system, for example, will incorporate three chainrings at the front and nine sprockets at the back. Changing the gear ratio will allow you to cover more or less ground while maintaining the same pace, so tackling a steep incline or taking advantage of a downhill is never out of the question.


Written by the How It Works team


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