How Do Bike Gears Work – Bicycle Transmission Explained

One thing about life is knowing when to pick up or slow down the pace. As much as it would be stimulating to keep charging hard, you’d wear yourself out. This is especially true when it comes to pedaling effort, and not just a philosophy of life.

Bike gears or transmissions can seem complicated at first sight, not to mention the technical terms, and of course the moving parts, but understanding them will improve your riding tremendously. In this guide, we get into the nuts, and bolts of bike gears, and most importantly you will actually understand how they work. Do yourself a favor, and follow through!

What are gears on a bike?

One of those wonderful technologies that make biking faster, easier to climb hills, and more enjoyable is the use of gears.

The energy you exert on the pedals is turned into output at the wheel thanks to the gears. Your legs can only exert a certain amount of effort, and there is often a max cadence at which you will be most effective.

You can travel more rapidly by shifting gears in line with the terrain and environmental factors to make the most out of your pedaling effort. Bikes may change gears using a number of various ways, but the external drivetrain is by far the most popular.

What determines the number of gears you have?

The rear derailleur shifts the gears on the cassette, which is a series of sprockets on the back wheel. This moves the cassette’s chain up or down. The chain is forced onto a larger or smaller sprocket as the derailleur shifts to change gear by traveling up or down.

The number of chainrings at the front and the number of sprockets at the back are simply multiplied. It is therefore possible to use all 10 sprockets in line with each of the three chainrings on a bike that has three chainrings and a 10-speed rear cassette. Similarly, a double chainring with an 11-speed cassette makes a 22-speed combination, and so on.

Why do you need gears on a Road Bike?

Road bikes, if you don’t already know, are bikes made for fast acceleration, higher top speeds, and reaching greater distances… on flat, smooth roads. These are the bikes that you see on the Tour De France. Naturally, they are designed for performance, trying to generate the most speed from the least amount of effort, one of the many components that allow that is gear speeds. 

When descending or riding at a fast pace, a high gear, also referred to as a “large gear,” is ideal. The largest front chainring combined with the smallest rear cog or sprocket produces the highest, or biggest, gear on a bicycle.

Combining the smallest front chainring with the largest rear sprocket produces the lowest gear, which will help you keep the pedals turning when the road inclines steeply up instead of down.

You wouldn’t be the first to say “well let’s just add more gears to a bike, and blaze away”, unless you found a way to break the laws of physics, that’s not possible. All high-end carbon fiber road bikes that are precisely constructed to meet competitive regulations can only take you so far, which is still impressive.

Why do some people prefer a single-speed bike?

Single-speed bikes or as commonly known as fixie bikes have been all the rage with the rise of hipsters. It’s not necessary to ride a bike with gears; some individuals prefer single-speed bikes. These still have a fixed gear, and the size of the front chainring and the rear cog define it.

But why give up the ability to effortlessly go over hills, and have higher speed, it would seem counterproductive at face value. Since fixie bikes require less maintenance and have fewer moving parts to damage, they are popular among commuters who live in flat locations and want to relax when they bike. 

One thing that not many people realize is that riding a fixie bike is also a great training tip if you are in competitive sports. Think about it, you are riding up a steep hill with increased effort, no way to make it easier, you will shed body fat, and body weight like it’s nothing. It’s a real cardio workout though, and we would recommend working up to that instead of going “gung ho”.

Types of Bike Gears

Cassette ratios

The smallest sprocket size is typically 11t or 12t whereas the largest sprocket size is indicated by the second digit such as 25. A common cassette ratio is 11-25.

Standard Double

Standard double setups are typically used for racing since they provide the largest chainring sizes for the largest gears that can be used to keep you pedaling smoothly at high speeds. Two front chainrings are linked with 9, 10, 11, or 12 rear sprockets. A standard chainset is a 53-39t combination, we mentioned it just so you know it as a fact.

If you want low gears, a normal double is not the greatest option because it is only feasible to reduce the lower gearing as low as a 38t. We will get to that in a bit.


In essence, a compact is a double setup that is scaled down. A 48t or 50t outer chainring is typically coupled with a 34t or 36t inner chainring to lower the gear ratio over the whole range.

It is a very popular option since the drop in gearing at the lower end is sufficient for most people to handle, and there is still enough top gear to allow for rapid descending. It’s the alternative to the standard double. 

PMP 33t chainring

As a quick patch to slightly lower the compact gear ratio. The common 34t ring is simply replaced by PMP’s 33t ring.


Semi-compact chainsets come with bikes that have a double-ring setup. The semi-compact chainset features a 36t inner ring and a 52t outer chainring. 

  • On the inner ring, the placement is 3 teeth smaller than the standard followed by 2 teeth bigger than the compact 
  • On the outer ring, the placement is 2 teeth larger than the compact, followed by a tooth smaller than the standard. 

The 36 inner rings may be coupled with an 11-28, 11-30, or 11-32 cassette which in practice is enough to handle anything that’s on a steep incline, while a 52t at the front provides a larger gear for quick descending, and even racing. You’ll have the best out of both worlds.


It is possible to offer a much smaller gear choice when there are three chainrings. A big ratio rear cassette with the third chainring, which is often 30t or smaller, may produce an exceptionally low gear for use on steep ascents. 

For riders who frequently ride in rough mountainous areas, a triple is a preferable alternative. If you’re on a long bike trip with extra cargo, the triple will make your life a bit easier.

Hub Gears

A universal gear system that requires little maintenance and is contained in a large rear hub is still popular with riders all over. The well-known Rohloff hub offers 14 speeds, while manufacturers like SRAM and Shimano also provide versions with as many as 12 speeds.

Hub gears are often reliable and low-maintenance, making them ideal for regular commuter bikes. Most hub gears also let you switch ratios without pedaling, which is useful in a pinch. Their major drawback is their weight, which is counterintuitive on long trips and turns against you on steep terrains.


The SRAM AXS groupset features smaller chainrings; the choices are 50/37T, 48/35T, and 46/33T. The 12-speed cassette’s gears increase by one tooth every gear starting with a 10-tooth cog on the back. As a result, your smallest gear is even simpler to push and you may attain a larger resistance at the top.


A new generation of “super-compact” gearing began with Apex. The Apex gearing system has a small double chainset, but to substantially lower the gearing, it uses a specifically created rear derailleur and a big ratio cassette with a range of up to 11-36 teeth.

This gives a top gear that is comparable to or greater than a triple in addition to a bottom gear that is lower even than a triple. 

How do bike gears work?

You will have a shifter located on the handlebar, the shifter basically allows you to change the speeds, and gear appropriate to the circumstances.

Trigger shifter

The most popular design in use today is the trigger shifter. It includes two levers underneath the bars that you may use your thumbs or fingers to adjust up and down.

Grip shifter

With a trigger shifter, you can often only change one gear at a time, while a grip shift allows you to swiftly switch between several speeds. You may change gears by turning the shifter, which is integrated into the grip on your handlebars.

Thumb shifters

Thumb shifters still exist but in a little more retro form. To shift through your gears, you turn a lever on top of your handlebars in either a clockwise or counterclockwise direction. Today’s gears are indexed, so shifting gears is as simple as clicking the gear shifter.

Your cranks’ input is transformed into output at the back wheel by your gears. Depending on whether you are in high or low gear, your pedaling is translated into different speeds. Typically, gear inches are used to measure your gear development, or how far your bike goes with each pedal.

With ranges around 20-30 inches being easy, 40-70 inches being medium, and +90 inches being very hard, gear inches may give you a decent sense of how hard or easy the gears are.

How do road bike gear shifters work?

Road bikes are a special case when it comes to gear shifts. Since the handlebar is tremendously different from your typical bike, naturally you will find some clever engineering. We will give you a hint though, it’s all in the brake levers.

Road bikes will include a shifter handle, right behind the brakes. Depending on the manufacturer, the shift handle can either be pulled back individually or alongside the brake handle. Some manufacturers include a thumb-slide you can use alongside the shift handle.

To avoid confusion many manufacturers give the shift handle a distinctive color, or textured rubber to differentiate it from the brake handle. All in all, it’s a clever way to make use of curved handles, and be as streamlined as possible.

How does electronic shifting work?

Metal cables have been the industry standard to actuate gears, this has been the case for a long long time. However, the rise of e-bikes has brought the rise of e-shifters for the e-drivetrains… sign of the times.

The gear is moved by a motor that is electronically instead of wires. The main advantage is constancy. While wires can sag and stretch with use, an electronic drivetrain will always retain precise shifting.

Batteries need to be charged, and they are currently expensive, so that is a downside.

Shimano Di2

Shimano’s electronic Di2 groupsets operate on the same principles as typical shifters. While the right shifter controls the rear derailleur, the left shifter controls the front. 

On each shifter, there are two buttons located behind the brake lever. The chain will be moved up from the little ring to the big ring on the left by pressing the thinner, dimpled inner button. The chain will be moved from the big ring to the little outside ring by pressing the button.

If you’re riding faster, the smooth outer button on the right shifter will pull the chain toward the higher gears, while the inner dimpled button will send it up the cassette to the lighter gears.

Campagnolo Super Record EPS

The Campagnolo Super Record EPS shifters have a thumb button within the shifter hood and a button behind the brake lever.

The button beneath the brake lever on the right-hand shifter will push the chain up the cassette into a lower gear. The thumb button will reverse this action and shift the chain’s back gear. If you press the button down while using EPS, the chain will move through several gears until you let go of the button.

The paddle button behind the lever on the left-hand shifter will transfer the chain from the smaller inner ring to the bigger outer ring.


The SRAM AXS uses a similar operation. The cassette’s right-hand paddle button, located behind the brake lever, shifts the chain into a higher gear. The chain is advanced up the cassette into a lower gear by pressing the left-hand paddle button.

You have to press the left-hand and right-hand buttons simultaneously to shift the chain between the two front chainrings; depending on its initial position, the chain will then go up or down.

How do I use gears on my bike?

As you can understand, there’s no universal way to shift gears, it will all depend on the bike that you are riding. Don’t feel overwhelmed because it only takes a little bit to get used to, and shifting gears will be very easy. 

What gear should I be in?

Efficiency is the main point of gears. For example, pedaling up a steep hill while in high gear would be a hard workout, and you run the risk of injuring your knees. Instead, you may pedal faster in a lower gear since your force input at the pedals is reduced, consistently going up without much pressure on your legs.

You use about the same amount of energy in each scenario. By having the force input necessary, you may pedal twice as quickly since the work is equal to the force and the distance.

At the same time, low gears will make you unstable on a flat surface, the lack of resistance makes you wildly pedal, so you switch to a high gear where your effort is directly channeled into balance and acceleration.

When should I shift my gears?

It’s all about rapid adaptation, especially if you are on inconsistent terrain.

  • Change to a lower gear to compensate for your increased effort when riding up a hill or riding against the wind.
  • Expect that you will need to slow down, and change into a lower gear so you can maneuver in tight corners. Think of Formula 1, you don’t just go full throttle on a tight turn, you will fly off the side.
  • If you are in an urban environment, low gears are helpful so you don’t overdo acceleration. In these environments, fine control is your safest option. When you cross in a path that’s free of cars, relatively straight, then switch to high gear, and blaze away.
  • Just like race car driving, you can’t switch gears on extreme ends rapidly, you run the risk of destroying them, or derailing the chain. You gradually shift gears, until you find the sweet spot.

The Finish Line

Since the gears on a bike make your pedaling experience all-around better, it’s a no-brainer that knowing what they are, and how they function is an extremely helpful thing. Gear shifting allows you to get the most distance, and speed with the least amount of effort, after all a human body, is capable of so much. 

We believe a practical approach is obviously better, so after learning this, while practicing everything will simply “click” in your mind.

Do be part of the pack and check out some more articles if you liked this one and found it helpful! 

Leave a Comment