- Bicycles have gears to help you ride more efficiently
when going uphill, downhill, and on the flat
across all varied terrain.
Without easy gears, you'd grind to a halt
when trying to go up steep hills
and without bigger gears, well you wouldn't be able
to pedal fast enough when going downhill.
But how do gears actually work?
Well in this video, we're going to show you.
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Before we explain how bicycle gears work,
we first need to explain the different parts,
beginning with the shifters.
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These are located on the handlebars
and are used to change gear.
On older bikes, these used to be located
on the downtube here, but on modern bikes,
they're on the bars.
They can be like this or like this.
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Next, we have the cassette.
This is the collection of different sized cogs or sprockets
on the rear wheel.
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These are the chainrings and they're turned by the pedals.
Bikes typically have one, two, or three chainrings.
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The chain connects the chainrings with the cassette.
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We then have the derailleurs, one at the back,
and if you have more than one chainring,
you'll have one at the front too.
The derailleurs are called derailleurs
because they literally derail the chain,
guiding it from one sprocket to the next
as they move from side to side.
Most derailleurs move from side to side
thanks to a cable that is connected to the gear shifter.
When you click the shifter, it pulls the cable tighter,
which in turn, pulls the derailleur
a measured amount up the cassette.
This also compresses a spring.
To shift down, clicking the shifter releases the tension
in the cable and allows the compressed spring
to now extend a measured amount
to guide the chain into the next gear.
The most high tech components don't have cables,
but are now self-contained electronic systems.
Instead of the cables actuating the gear change,
the derailleurs move using
little electronic motors called servos.
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The rear derailleur contains springs
and this cage with little pulley wheels in,
which help guide the chain
and, crucially, keep it under tension.
This is important because without it,
changing the size of the gear could make the chain slack
and then, it would slip.
To help with the changing of gears and make it smoother,
the teeth on the cassette and chainrings
are specially shaped with little ramps
to help guide the chain.
Bikes have gears to help you with changes in gradient
and if desired, to increase speed on the flat.
The smallest chainring at the front,
paired with the biggest cog at the back,
is the easiest gear, ideal for steep climbs
or setting off from a standstill.
If your chainring has 34 teeth
and your biggest cog at the back also has 34 teeth,
that is a one to one gear ratio,
a relatively easy gear to turn.
The rear wheel will turn once for every pedal stroke.
At the opposite end, if you shift into your fastest
and hardest gear, the ratio is much bigger.
For example, if your biggest chainring is 50
and your smallest cog at the back is 11,
that results in a ratio of 4.55,
meaning the rear wheel will spin 4.55 times
for every one rotation of the pedals.
This is a harder gear to get going,
but is useful once you're traveling at speed
or going downhill.
I hope you found this video useful and informative
and that you now know how bicycle gears work.
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