One More Gear for 4x Cost: the Difference Between 21- and 22-Speed Bikes

Bicycle specification numbers may obscure quality and performance. 22-speed drivetrains support a wider range and smoother shifting than 21-speed but at a higher price.

Bicycle drivetrains. Bottom: Giant Escape 3 from https://www.giant-bicycles.com/us/escape-disc-3. Top: Trek Checkpoint ALR5 from https://media.trekbikes.com/image/upload/f_auto,fl_progressive:semi,q_auto,w_1920,h_1440,c_pad/CheckpointALR5_22_35172_B_Primary

Bicycles can be complex machines, offering plenty of customization options to craft the perfect bike tailored to your needs. However, understanding all the numbers and specifications can be a challenge, especially when all you want to do is get on the saddle and ride. Sometimes, values that appear similar on paper can make a significant difference in the quality of the bike.

Don’t let yourself feel overwhelmed and abandon biking for fitness. Cycling provides unique opportunities over other physical activities. In particular, I found biking a lot less stressful on my body than running, especially when I was first getting into shape.

If confusing information is the main problem keeping you from riding, I’d like to help. While I’m interested in demystifying specs on all of the significant components of modern bikes, let’s start with a small but educational demonstration of gearing differences.

There are many common options for gear configurations. To make this simple, I’m going to compare the drivetrains of two bikes that I have personally owned: the 21-speed Giant Escape Disc 3 and the 22-speed Trek Checkpoint ALR 5. Their specifications appear quite similar at first glance, yet the Checkpoint is nearly four times the cost of the Escape.

To be clear, there’s nothing wrong with an entry-level bike. My Giant Escape 3 lasted nearly ten years and multiple 100+ mi rides. The purpose of this article is about why prices are so different so you can make an informed decision about what suits you best.

Figure 1: Selected specifications of the two bikes may look similar but the prices aren’t the same at all.

Several features justify the higher price of the Checkpoint, but let’s just explore how the Checkpoint offers a superior drivetrain with just one additional speed.

Terminology

From an engineer’s perspective, a bike doesn’t have gears at all! The toothed wheels we generally call “gears” are cogwheels. It’s only a gear if it’s interlocked with another gear:

Figure 2:Venn diagram of different cogwheel types. Most bicycles use a chain or belt-powered drivetrain so they have sprockets, not gears. https://www.flaticon.com/free-icons/gear & https://www.flaticon.com/free-icons/sprocket Gear icons created by Dave Gandy, freepik, and Flaticon

Let’s clarify some bike terminology to ensure you, me, and your local bike shop are on the same page:

Figure 3: Key components of the drivetrain https://www.freepik.com/free-vector/realistic-bicycle-set-with-different-models-illustration_13805753.htm on Freepik

Drivetrain: The collective name for everything on a bike that translates pedal force into travel distance. It includes pedals, crankset, chain, cassette, and the rear wheel.

Chainring: A cogwheel in the front of the bike. Bikes can have one, two, or three chainrings. Chainring shifting is typically controlled by the left hand. In this article, these will always be called “front chainrings” to distinguish them from the sprockets in the rear.

Crankset/Crank: The name for the component made of front chainrings, the spindle, and arms where pedals attach.

Figure 4: Shimano GRX 2x crankset from https://bike.shimano.com/en-EU/product/component/grx-11-speed/FC-RX600-11.html

Sprocket: A cogwheel on the rear wheel axle. In this article, we’ll use the term “rear sprocket” to avoid confusion with the front chainring. In engineering, any cogwheel attached to a chain is a sprocket but in biking, sprocket specifically refers just to the cogwheels on the rear wheel.

Cassette: A group of rear sprockets. Cassettes can contain anywhere from one to twelve sprockets. The right-hand shifter usually switches between sprockets. Cassettes are often advertised by “speed” (e.g. 10-speed = 10 sprockets) and min-max sprocket size (e.g. 11–42T indicates that the smallest sprocket has 11 teeth and the largest has 42).

Figure 5: Shimano cassette of eleven sprockets (11-speed 11–34T GRX). The tooth count is engraved in the upper left of each sprocket. From https://bike.shimano.com/en-EU/product/component/grx-11-speed/CS-HG800-11.html

Gear/Gearing: A specific combination of front chainring and rear sprocket.

How Gearing Works

The bike drivetrain is a series of simple machines that provide a Mechanical Advantage (MA). The MA of a gear is proportional to the ratio of the number of teeth in the front chainring vs. the teeth in the rear sprocket, or Gear Ratio (GR). GR (and MA) increases as front chainrings get larger and rear sprockets get smaller.

GR also describes the number of times the rear wheel spins for each rotation of the pedal. For example, a GR of 3 means that one revolution of the pedals will spin the wheel three times. A bike with a standard 700 mm wheel would travel at least 6.6 m (21.6 ft) per crank rotation (excluding coasting). GR = 1 would travel just 2.2 m.

MA has a trade-off: the more the back wheel travels per pedal revolution, the more force you need to apply to those pedals.

Our legs have a small comfortable range for both cadence and pedal force. Most casual riders can maintain around 60 RPMs while applying about 100 N of force to the pedals. The best MA at any time is the one that allows the rider to match both of these targets.

Gearing allows the rider to optimize the GR: lower gear on hills or accelerating, high gear when maintaining a high speed. When a rider maintains a consistent cadence of 60 RPM, they are at a “cruising speed” that is proportional to GR. More gears on a bike accomplish two goals:

1. Provides a wide range of comfortable cruising speeds

Figure 6: Speed at 60 RPM and 700 mm wheels based on GR. Note: all other factors being equal, the force required to maintain cruising speed increases with GR.

2. Ensures optimal MA throughout that range.

Smaller changes in MA between adjacent gears mean that cadence and applied force won’t vary much after shifting, making gear transitions more comfortable and improving efficiency. Typical single-sprocket shifts in the rear cassette change the MA by around 10–15% but can be as low as 6%.

Figure 7: MA change profile of a typical 11-speed cassette. Shifting between adjacent sprockets changes the MA between 8–18%.

Very large changes in MA (25% or more) require a few seconds for the rider’s legs to adjust to the new pedaling speed or force. I refer to these uncomfortable shifts as “wolf intervals,” repurposing an old music term.

A shift between front chainrings is a prime example of a wolf interval. The MA change can exceed 50% on some bikes. Experienced riders learn to counter-shift the rear cassette along with the front chainring to minimize the impact of the wolf.

Figure 8: Graphical demonstration of a counter-shift in a GRX 11-speed drivetrain. Each rear sprocket is given a unique color. The initial front chainring shift from small to large increases the MA by 50%. The rider quickly downshifts the rear cassette by three sprockets (four shifts, total) to ease the MA transition (17% final delta).

22 is much better than 21 (except blackjack):

A good drivetrain offers a wide range of gears with minimal MA differences between each shift. Now let’s compare the two bikes:

The Escape 3 has a 3x7 drivetrain (3 front chainrings, 7 rear sprockets) for a total of 21 gears. The Checkpoint ALR5 is a 2x11 (22 gears). Here is a graphical representation of every gear of the drivetrains by GR:

Figure 9: Each dot represents a chainring/sprocket combo (larger sprockets have lower GR). Near-redundant gear clusters identified with boxes. Gear Ratio uses a log scale to accentuate the percent difference in MA between adjacent gears.

I’ve identified certain clusters as near-redundant gears, which meet two criteria:

1. Less than 6% change in MA
2. Requires at least 3 shifts to transition

It is too challenging to transition between these gears with too little benefit. Each gear in a near-redundant cluster still has use cases but the cluster only offers one practical GR.

After consolidating near-redundant gears clusters, only 12 effective gears of the Escape’s 21 speeds remain. The Checkpoint ALR5 offers 16 effective gears. Those extra non-redundant gears in the 2x11 setup provide four advantages over the 3x7 drivetrain:

1. More low MA gears.
2. One higher gear. Top gear MA/cruising speed is 20% higher.
3. Additional effective gears in the mid-range.
4. Fewer wolf intervals from front chainring shifts.

In particular, the large MA delta between the two largest sprockets on the Escape 3 can leave riders stuck in a low gear without an easy way to shift out of it. In contrast, the Checkpoint’s 11-speed 11–34T cassette covers the same range with three sprockets and a maximum MA difference of 13%.

Figure 10: The 7-speed cassette on the Escape 3 has a big change in MA between the two largest sprockets. The 11-speed cassette on the Checkpoint ALR5 has additional sprockets through this range.

You get what you pay for, even if it’s hard to tell:

There are many differences between a $600 bike and a $2500 bike (fork material, grade of Al frame, frame construction, hydraulic brakes, drop handlebars, and tubeless tires, to name a few).

The drivetrain is one significant example where the differences may not be obvious but may be very important based on riding style. If you are not a skilled bike mechanic, you are more or less stuck with the gearing you have.

The true value of a bicycle may be hiding in the specs. It may require some analysis on your part to find the right bike for your needs. The benefit a 22-speed drivetrain offers over 21-speed is a lot greater than it sounds.

I am the sole author of the initial draft of this article. The final responsibility for the accuracy and quality of this article rests with me. ChatGPT helped enhance the readability and clarity of the published work by providing suggestions and improvements that refined the draft.