Everything you need to know about 12-speed road drivetrains

The cycling world is constantly evolving. Every year, new designs and technologies come to market aimed at ever-increasing rider efficiency. This is partly ensured by the drivetrain, as it transfers your pedalling effort to drive the rear wheel. Made up of all the sprockets, the cassette is your bike's gearbox, allowing you to progress by selecting the right gear.
Drivetrain options have diversified considerably with the emergence of ever wider and more extended cassettes. Today, the 12-speed drivetrain marks a new step forward in the pursuit of optimal performance. Here is the key information to help you make the switch!

What are the advantages of a 12-speed drivetrain?

The 12-speed drivetrain offers several advantages:

• Better-spread tooth count

  Your 12-speed drivetrain allows an extra sprocket a to be fitted to the cassette for smoother gear changes, without too large a jump in development. For example, Campagnolo offers cassettes in which the first seven sprockets follow one tooth at a time. This is a comfort advantage, as it is on the smallest sprockets that each gear change is most noticeable in terms of development, and therefore change in pedalling cadence.
  Choosing the right cassette provides riding comfort and greater versatility. The twelfth sprocket proves pleasant for filling a gap in the gear ratio combination.

• A wider gear ratio range

  Indeed, thanks to the additional chainring you can extend the spread of your cassette with a smaller or larger sprocket at the extremities b. A large gap between sprockets allows you to tackle a wide variety of situations, from flat terrain to very steep climbs.

Key points

• SRAM, Campagnolo and Shimano drivetrains
• Drivetrain type: mechanical or electronic
• Single or double chainring
• Brake type: disc or rim
• Freehub body compatibility: Campagnolo ED, Shimano HG and SRAM XDR
• Mounting options

Market players

American brand SRAM is an undisputed leader in drivetrains. By introducing 12-speed in the MTB sector in 2015, it gained significant experience in this segment. Its two flagship groupsets, named Red and Force eTap AXS, feature 12 speeds and wireless electronic transmission. In particular, the cassette offers a first sprocket of 10 teeth paired with smaller chainrings. This allows for a wider range of gear ratios, with closer gaps between each sprocket.

Always a pioneer in the drivetrain field, the Italian brand offers prestigious products of a high technological standard. As mentioned above, Campagnolo chooses to add a sprocket in the middle of the cassette to smooth gear changes. It retains traditional chainring combinations and an 11-tooth starting sprocket.

To mark the Japanese brand's centenary, Shimano launched two groupsets from the Dura-Ace R9200 and Ultegra R8100 ranges. These new top-of-the-range Di2 12-speed electronic groupsets are available in 11-30 and 11-34 configurations to widen the gear range. This makes it possible to retain an 11-speed compatible freehub, using the technology employed for better use of your wheel on the road and on a turbo trainer. In addition, the sprocket progression is linear, with no sprocket jump in the middle of the cassette.

Mechanical or electronic?

The main difference between an electronic and a mechanical drivetrain is the ease of use that electronic shifting provides. Indeed, there is no longer any difficulty in changing chainring at the top of a climb or shifting gears in the rain and cold. Mechanical drivetrains also require more regular maintenance and wear out more quickly. For electronic drivetrains, the main drawback lies in the risk of a failure during a ride and a higher price.

Campagnolo offers the Super Record EPS groupset. The choice is wider in mechanical with three different groupsets: Super Record, Record and Chorus. On the SRAM side, the American brand is only available in electronic drivetrains with the Force Etap and Red Etap groupsets. It also offers a single chainring Force 1 version for those who would like to try a single chainring setup. At Shimano, two groupsets are available in 12-speed electronic drivetrains: the Dura-Ace R9200 and the Ultegra R8100.

Single or double chainring?

This growing number of available gear ratios allows development to be taken even further, by switching to a single chainring in Cyclocross or Gravel, following the trend already established in MTB. Gear changes are therefore easier to manage, with only one lever to use. It also ensures an optimised chainline as the single chainring is recentred relative to the cassette. You will gain weight savings, aerodynamic benefits and easier maintenance.

However, using a double chainring provides a much wider range of gear ratios, which is beneficial on the road, particularly if your route includes varied terrain.

Braking

At Campagnolo, Shimano and SRAM, all groupsets available in 12 speeds are compatible with rim brakes or disc brakes.

Disc brakes offer several advantages: better braking power in all weather conditions, no wear on the rim surface and an end to problems with cables oxidising or seizing. They provide braking that is not only powerful but also progressive, which considerably reduces stopping distances. In addition, as less effort is required on the lever, the cyclist can ride more relaxed.

That said, it is important to note that disc brakes are heavier than rim brakes and therefore add extra weight to your bike. Furthermore, this type of brake requires more rigorous maintenance and more specific adjustments, which can make servicing the bike somewhat more demanding.

Compatibility

A groupset consists of components designed to work together. Haphazard combinations of different accessories should therefore be avoided. Such builds do not guarantee correct operation and only a complete groupset from the same brand guarantees optimal use. In any case, switching to a 12-speed drivetrain requires a complete drivetrain overhaul, namely: cassette, chain, derailleurs, levers and crankset.

Campagnolo makes it possible to fit a 12-speed cassette on an 11-speed cassette body, since it uses the same spacing. It is therefore possible to keep the same wheels, provided they are equipped with a Campagnolo ED cassette body.

The configuration is identical at Shimano, where the 12-speed cassette is compatible with a wheel fitted with an 11-speed HG freehub body.

For SRAM, the first 10-tooth sprocket requires fitting a specific XDR cassette body, but many brands offer XDR freehub bodies for their wheels. XDR freehub bodies are compatible with all XD cassettes when the cassette is installed with a 1.85 mm spacer behind it. Again, it is therefore possible to use your existing wheels with this modification.

The different mounting options