Shimano cassettes and chainrings: how to choose the right sprocket sizes and gear ratios

Dura Ace CS-R9200 12s cassette, Ultegra or 105: here is our guide to choosing the right sprocket sizes

The cassette is a central component of a road bike's drivetrain. It determines the range of gear ratios available, the pedalling cadence and the efficiency both on climbs and on the flat.

With the arrival of 12-speed road drivetrains, manufacturers have been able to offer more progressive gear steps and better management of ratios. High-end cassettes thus allow a more regular cadence and a more efficient drivetrain.

In this guide, we analyse the different sprocket sizes available on 12-speed road cassettes, their gear steps and how to choose the one that best suits your riding.

View the Dura Ace CS-R9200 12s cassette

The main sprocket sizes for 12-speed road cassettes

Modern road cassettes generally exist in several sprocket combinations in order to suit different terrain profiles.

Cassette	Sprockets	Use
11-28	11-12-13-14-15-16-17-18-19-21-24-28	performance and fast-rolling terrain
11-30	11-12-13-14-15-16-17-19-21-24-27-30	versatility
11-34	11-12-13-14-15-17-19-21-24-27-30-34	mountains

Understanding sprocket gear steps

The gear step corresponds to the gap between each sprocket. The smaller the gap, the more regular the pedalling cadence remains.

11-28 cassette

Sprockets:

11 → 12 → 13 → 14 → 15 → 16 → 17 → 18 → 19 → 21 → 24 → 28

• very close gear steps
• precise cadence
• ideal for racing

11-30 cassette

Sprockets:

11 → 12 → 13 → 14 → 15 → 16 → 17 → 19 → 21 → 24 → 27 → 30

• good progression
• versatile on flat and rolling terrain
• excellent compromise

11-34 cassette

Sprockets:

11 → 12 → 13 → 14 → 15 → 17 → 19 → 21 → 24 → 27 → 30 → 34

• larger gaps
• easier gear ratios
• ideal for the mountains

Gear range

Cassette	Ratio	Use
11-28	2.54	compact
11-30	2.73	versatile
11-34	3.09	mountains

The higher the ratio, the easier the gear the cassette offers for steep climbs.

For example, a Shimano Dura Ace CS-R9200 12s Cassette is offered in these different sprocket sizes in order to cover fast-rolling routes as well as mountainous terrain.

Gear development table with a 52-36 crankset

The development corresponds to the distance covered with each pedal revolution. Here is an example with a 52-36 crankset and a 700c road wheel.

Sprocket	Development 52 teeth (m)	Development 36 teeth (m)
11	9.93	6.87
12	9.10	6.30
13	8.40	5.82
14	7.80	5.40
15	7.28	5.04
16	6.83	4.73
17	6.43	4.45
19	5.76	3.98
21	5.21	3.60
24	4.55	3.15
27	4.04	2.80
30	3.64	2.52
34	3.21	2.22

Which cassette should you choose for your riding?

11-28: for performance

• fast-rolling terrain
• races
• very precise gear steps

11-30: the most versatile cassette

• varied rides
• rolling routes
• excellent compromise between cadence and ease

11-34: for the mountains

• long climbs
• significant elevation gain
• easier gear ratios

FAQ on 12-speed road cassettes

Which cassette should you choose for the mountains?

For routes with a lot of elevation gain, a cassette with a large 34-tooth sprocket provides an easier gear and allows you to maintain a high cadence on climbs.

What is the difference between an 11-28 and an 11-30 cassette?

The 11-28 cassette has closer gear steps, which improves cadence precision on the flat. The 11-30 cassette offers a slightly wider gear range and is more versatile.

Which crankset should be used with a 12-speed road cassette?

The most common cranksets are the 52-36 or 50-34 combinations, which offer a good balance between speed on the flat and ease on climbs.

What are the features of the Shimano Dura Ace CS-R9200 12s Cassette?

The Shimano Dura Ace CS-R9200 12s Cassette is a high-end road cassette designed for Shimano Dura-Ace groupsets. It stands out for its optimised gear steps, its lightweight construction and the Hyperglide+ technology which improves shifting speed.