Bike Gears and Shifting Basics
Understanding how your bike gears work can help you choose the right components when you’re bike shopping. It will also help you get the most enjoyment out of your bike when you’re out on a ride.
Understanding the Bike Drivetrain
There are five main parts of the standard bicycle that let you shift gears and change how easy it is to pedal your bike. They are comprised of the following:
- front chainrings (a.k.a crankset)
- rear cassette
The crankset, rear cassette, chain and derailleurs are known collectively as the drivetrain, pictured here:
Chainrings: Bikes have one, two or three front chainrings, also known as the crankset. A bike with two chainrings is called a double. A bike with three chainrings is called a triple. Each chainring has a number of teeth on it where the chain connects.
Cassette: Your bike’s rear cassette is the stack of cogs (gears) mounted on the right-hand side of your rear wheel, with the small cog farthest from the wheel and the large cog closest to the wheel. Each cog has a number of teeth on it where the chain connects.
Chain: The chain connects to the teeth on your front chainrings and the cogs on your rear cassette so that when you pedal, the chainrings and cogs turn the wheels and the bike moves forward.
Derailleurs move the chain between the front chainrings or between the rear cogs. Cables run from your shifters to your derailleurs. When you press on your shifter, it moves your front or rear derailleur so the chain moves where you want it to go.
Many bikes have front and rear derailleurs. Some mountain bikes have only a rear derailleur and therefore come with only one shifter. (These bikes have more cogs in the rear cassette, giving you a broad range of gear choices even with a single front chainring.)
Shifters let you move the chain between your front chainrings and the cogs of your bike’s rear cassette. Each shifter controls one cable attached to one derailleur.
On road bikes, the shifters are mounted either on the handlebar or they’re integrated with the brake levers. In older road bikes, they’re on the downtube or on the ends of your drop bars. On mountain bikes, the shifters are mounted on the handlebar.
Alternative Components for Bike Drivetrains
Electronic shifters: Instead of cables, electronic shifters use wires and a battery powers the shifting. It’s more like clicking a mouse than pressing a lever. The system needs to be charged to work, and it can be pricey.
With electronic shifting, the chain will always move precisely and won’t mis-shift. You can shift on hills, even with pressure on the pedals. It’s an excellent solution for riders who have weak hands or other limitations that make shifting gears difficult.
Internally geared hubs: Instead of derailleurs, internal hubs have the shifting mechanisms inside the hub of the rear wheel. Internal hubs can work with a chain or a belt drive. Because all of the moving parts are completely protected from water, dirt and grime, internal gear hubs are lower maintenance than conventional cassettes, but they are limited in how many gears they can provide.
Belt drives: Some single-speed and internally geared bikes use a belt drive instead of a chain to move the bike forward. The most popular belts are made from urethane and carbon fiber. Belt drives are stronger, quieter and cleaner than a chain, with less maintenance.
Types of Shifters
Regardless of shifter style or type of bike, one shifter controls the front derailleur, and one controls the back.
Road Bike Shifters
Most road bikes have shifters integrated into the brake levers of the bike. They’re easy to reach and in your field of vision, so you don’t have to take your eyes off the road to shift. Older and lower-budget road bikes have shifters mounted on either side of the stem, on the downtube, or in the bar ends.
Mountain Bike Shifters
There are two styles of shifters popular on mountain bikes:
Thumb shifters have two levers for each hand—one lever moves the chain up through the gears and one moves the chain down. On one hand, the top lever makes the gears harder, and on the opposite hand the top shifter makes the gears easier.
Grip shifters let you switch gears by twisting the indexed grip of your bike forward or backward. Like with thumb shifters, twisting one way moves the chain up through the gears and twisting the opposite way moves the chain down.
Using Your Shifters and Gears
Gears and shifters help you maintain cadence – a constant pedaling speed – during your ride. Generally, a higher cadence on an easier gear is more efficient than pedaling slower in a harder gear.
Pushing hard gears might seem faster, but it will sap your strength more quickly, and it can take a toll on your knees.
At a high cadence, you’re working in your aerobic zone, which means your muscles can clear lactic acid and postpone fatigue.
The optimum cadence for road biking is around 80–100 rotations per minute. For mountain biking, it should also feel like you’re spinning your legs, not powering slowly, though it’s harder to keep cadence on technical terrain.
Once you find a comfortable cadence, shift your gears to help you maintain that cadence for as much of your ride as you can.
Proper Shifting Technique
Shift the chain between the rear cassette cogs for small changes and between the front chainrings for big changes, but not both at the same time. Only use one shifter at a time, or you may mis-shift, jam the chain or drop the chain off the chainrings or cassette.
Try to anticipate the terrain, and shift right before you start climbing, not halfway up when you’re nearly stopped with maximum pressure on the pedals.
On flats, it’s okay to shift through several gears at a time. If you do shift on a hill, shift one gear at a time, and try to momentarily release pressure from the pedals as you’re shifting.
When you shift, don’t pick a gear that will put your chain on opposite extremes of the front cogs and rear cassette at the same time. Called cross chaining, this is where you’re most likely to drop or break your chain. Those same gears can be achieved with different combinations of chainrings and cogs.
Understanding Bike Gear Specs
When buying or upgrading a bike, you’ll need to decide how many gears you need, and also how your bike is geared. Both determine how hard or easy your bike is to pedal: how many times you turn the crank vs. how many times the wheel rotates.
How to read the specs: When shopping for a bike, you’ll typically see specifications like the following to indicate the number and type of gears:
|Rear cogs||11-34, 10 speed|
|Number of gears||30|
In this example, the three numbers in the crankset (48/36/26) indicate the bike has three chaingrings in the front (a triple). The specific numbers indicate how many teeth each chainring has: 48 teeth on the largest, 36 on the middle and 26 teeth on the smallest.
In the Rear Cogs spec, “10-speed” tells you that the there are 10 cogs in the rear cassette. The specific numbers indicate the range of teeth from the smallest to largest cog (11 teeth for the smallest to 34 for the biggest).
Because this bike has 3 chainrings in front and 10 cogs in back, it has 30 gears (3 X 10).
How gear size correlates with performance: In your front crankset, the larger chainrings with the higher numbers of teeth are for going fast, and lower numbers are for climbing. In the rear cassette, it’s the opposite. The bigger cogs with the higher numbers of teeth are better for climbing.
What Gearing Do I Need?
Bikes are available with a broad range of number of gears, from one to 30 or more. When you factor in the many combinations of multiple chainrings and cogs and the numbers of teeth on them, things can get complex.
To keep it simple, the most important things to consider are your fitness level and the terrain you'll be riding. If you'll be riding lots of hills and you find climbing challenging, then you'll want to opt for more gears.
If you're a strong cyclist or you only ride flat terrain, you won't need as many low gears to power up a hill so you can get away with fewer gears, which will keep your bike light.
Price is also a consideration when choosing the gearing for a bike. An 11-speed cassette gives you the smoothest shifting, but it's also the most expensive. 9-speed and 10-speed cassettes are more affordable, but there are larger jumps between gears so it can be harder to find the right gear for the terrain.
There are specific gear considerations based on the type of bike you have.
Most road bikes have at least 18 gears but can have 30 or more, depending on the number of chaingrings and cogs.
If you’re an average rider, not an elite athlete, it’s typically best to focus first on the low gears for climbing hills. Not being able to go quite as fast as you’d like on the flats is still more fun than walking up hills.
Smaller chainrings, also called lower gears, make climbing hills easier, so you can keep your cadence consistent in hilly terrain or over longer distances.
Standard cranksets for road bikes come with two chainrings. It's common for a standard crankset to include a 53-tooth large chainring and a 39-tooth small ring. A compact crankset has two chainrings that are smaller than the chainrings on a standard crankset to make pedaling easier when climbing hills. Compact cranksets usually have 50-tooth and 34-tooth rings, though other options are available.
If you live where it’s hilly, you will likely be happiest on a compact crankset. You can also add a third small chainring to give you a broader range of easy gears. However, you may need to update other parts, such as derailleurs and shifters, when you add the third ring.
Another way to alter the performance of your bike is to swap out the rear cassette. If you ride where it's mostly flat, choosing a cassette with a narrow range, like 11-25 (11 teeth on the small cog, 25 on the big cog) will let you find exactly the right gear while riding and will keep your shifting smooth. For rolling hills, a cassette with a 28-tooth large cassette will make going uphill easier. For mountainous areas, you're going to want a really low gear, so look for a cassette with a large cog that has 30 or even 32 teeth on it. The downside to cassettes with larger cogs is that they typically have a bigger jump between gears, which can make your shifting feel less smooth and make it more difficult to find the right gear for the climb.
Gearing options for touring bikes are very similar to those for road bikes. However, for a touring bike, you'll generally want to gear even lower than you would for a normal road bike since you'll be carrying camping gear, food and clothing. Bike tourers often opt for three chainrings up front; the third small chainring (sometimes called a granny gear) gives you a broader range of easy gears for climbing hills with a heavy load. Pair that third chainring with a rear cassette that has a large cog with 34 teeth on it and you'll have a nice easy gear for climbing.
Mountain bikers should also gear for the hardest climbs. Mountain bikes typically have 9-11 cogs in the back and 1-3 chainrings in front, indicated by 1x9, 1x10, 2x10, 1x11, etc.
Mountain bikes have traditionally come with two or three chainrings to provide a variety of easy gears for climbing. However, mountain bikes with single chainrings are now very popular. Bikes with one chainring are lighter and simpler because you'll need only one shifter to move through the gears on the cassette. Having only one shifter also leaves room on your handlbars for a dropper post remote, which lets you move the seat up and down on the go for excellent control on descents and efficiency on climbs.
However, one chainring doesn't give you as wide a variety of gears. If you find climbing challenging or regularly ride steep terrain, consider a double crankset, or even a triple. A common double crankset size is 38/24. That combined with a cassette that has a large cog with 36 teeth, will give you a great easy gear.
Bike Component Quality and Price
As your drivetrain components go up in price, they typically get lighter and more precise in their performance. However, the lightest parts sometimes sacrifice durability.
If you’re considering which components to upgrade, your biggest bang for the buck will be higher quality shifters and the cables that move your derailleurs. For example, shifters that rotate on ball bearings, instead of bushings, make it easier to shift.
For other components, moving up in price mostly means they will be lighter in weight.
Basic Drivetrain Maintenance
Keep your drivetrain running smoothly by cleaning it after you ride and lubing your chain. Whenever you clean your chain, check your cables. If they are frayed or rusty, take them into your shop for replacement. Once a year, have your shop remove your cassette, chain and chainrings to clean them in a parts cleaner.
Read our article, Bike Maintenance Basics article, for more details on keeping your bike in tip-top shape.