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Bike Gears and Efficient Shifting

Understanding the science helps juice the most out of any bike

When riding a bike, your body can only produce so much power before you run out of energy. Gears on a bike help you ride more efficiently and consistently so you can sustain your energy longer.

Understanding how your bike gears work can help you get the optimum performance out of your bike when you’re out on a ride.

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
  • Chain
  • Derailleurs
  • Shifters

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.

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:

  1. 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.

2. 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.

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.