How Bicycle Gear works | Simple and Detail explanation

Knowing the mechanism behind working of bicycle gear can help you choose the best suitable bicycle option with gear which suits your need and budget as well. To understand the bicycle gear, first one should familiarizes himself / herself with different part of drivetrain which together called as drivetrain 

Different parts of Bicycle Gear 

If you are already aware of different gear parts, you can switch to the next section of blog on how gear system works.

Chainwheel / Crank - The cycle crank is the part of the drivetrain close to the pedal area where the chain moves. When you apply pressure to the pedal, it rotates the chainwheel, which in turn moves the chain attached to the crank and transfers mechanical energy to the chain.

Cassette / Freewheel - When the chain starts moving over the front crank, it transfers energy to the chain, which in turn start pushing the rear sprocket to move. These sprockets are attached to the rear wheel, resulting in the rotation of the rear wheel.

Gear shifters  These are attached to the handlebar. When you wish to change gear, you press the shifter, which internally pulls the metal wire and forces the derailleur to move horizontally, pushing the chain to move onto different teeth on the front crank or rear cassette.

Derailleur - This is the part of the gear system used to move the chain onto different sprockets on the front crank or rear cassette area. When you press the gear shifter on handlebar, the wire attached from the gear shifter to derailleur gets pulled which in turn move the derailleur horizontally pushing the chain to switch gear

How Bicycle Gear system Works ?

The amount of energy you apply to push the pedal gets converted into rotational energy by the drivetrain mechanism. One can consider the legs as the engine of this two wheeler, which helps to move the cycle forward.

Since this engine, or pedaling effort, is operated by human powered leg strength, it is not feasible to apply the same strength all the time, considering different terrains like flat or uphill roads, or continuous pedaling for long hours. Hence, gear mechanisms help reduce the effort of pedaling so one can continue to pedal and move forward with less strength applied by the legs.

But this lower leg power required to pedal comes at a cost. As less pedal strength is needed, the number of pedal rotations will increase as well to cover the same distance. Since it is easier to pedal multiple times with less power to continue moving compared to either applying constant power or taking a stop to regain strength in the leg, the gear helps you keep moving and attain better average speed.

One can also Image the gear bicycle mechanism by relating it to gym cycling machine where you have a knob to reduce or increase the pedal effort based on your cardio level you are choosing. In case of gear bicycle in real life, you will feel the same effort changes in pedaling on road 

What are different gear system like 7,21 gear, 8 or 24 gear, 9 or 27 gear, 10,11,12,13 etc ?

 Gear mechanism in drivetrain work at 2 place
1) At the crank side where you can have 1, 2 and 3 sprocket to move chain , These are also called as front gear


2) at the rear wheel size also called as cassette 

  • 1X Gear - 7,8 9,10,11,12 Gear means only rear wheel side gear and front there is only one sprocket
  • 3X Gear - 21, 24, 27 etc gear mean there are 3 gear in front crank side and rear same gear 7 ,8 and 9. Combination of front and rear gear become 3 X rear gear numbers.

 This Video you can learn in details how gear system works

What is usage of front gears in a bicycle ?

The effort of pedaling depends on the sprocket where your chain is moving.

  • A higher number of teeth on the front crank or chainwheel is needed for more speed, while a smaller teeth sprocket on the crank or a smaller chainwheel is needed for climbing.
  • A smaller number of teeth on the rear sprocket or cassette is needed for speed, while a larger teeth sprocket or cassette is needed for inclined roads.

When we ride 1x drivetrain bike such as 7 , 8 , 9 speed bicycle, they are enough for small inclined roads but on steep roads or mountains the rear biggest sproket is not able to provide the enough support that we can climb the road and front gear lower chainwheel is needed 

How to Choose Right Gear combination for your usage?

To understand this, one need to learn basic of different bicycle categories as well
Hybrid Bike - Designed for city commute, comes with thin tyres. Hybrid bike an have suspension or can be without suspension as well

Mountain Bike / MTBThese bikes are ideally designed for off roading and trail riding. They have front or rear suspension option which thicker tyres size 

Learn Difference between Hybrid Bike and Mountain bike

Roadbike These are performance oriented bikes, designed for long rides or  speed. They are not suitable for off roading or trail riding. They have aggressive riding position which make them little uncomfortable for regular city rides as well

Now Lets come back to the point of choosing right gear bicycle 

  • If you are choosing are Hybrid bike and your purpose is city commute with some flyovers , 1x Drivetrain is most suitable. Less moving or gear mechanism reduce the service and maintenance as well . However if you are taking Hybrid bike on mountain or Hilly areas, 3X drivetrain is needed 
  • If you are choosing a mountain bike and riding will be in cities, 1x drivetrain is enough. Some steep flyover in case of Mountain bike, 3X drivetrain is needed. If you are riding on mountains than 3x or 1x11 and above drivetrain is needed 
  • Roadbike generally come with 2x drivetrain with front 2 chainwheel and rear chainwheel possibility of 8,9,10,11,12,13 making them versatile for all terrain usage

What is cross chain in gear bicycle?

Cross chaining happens when the bicycle chain is at extreme angles, for example, having the chain on the highest chainwheel of a 3x drivetrain on the front crank side and the highest sprocket of the rear cassette. Since the chain is not straight, the wear off / damage on the chain in this riding position is higher compared to other gear positions. The more diagonal the chain is, the less efficient the riding will be, resulting in more wear and tear. This can damage not only the chain but also, in the long run, other gear components where the chain is in motion, such as the chainwheel teeth or cassette teeth


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