What is the best drivetrain system for bicycles? Before answering this question, it's essential to understand what we're talking about and the key features of the drivetrain groups currently available in the cycling market. The bike drivetrain is the set of gears that enables the rear wheel's movement, powered by the rider’s pedal strokes.
Understanding the Bike Drivetrain System
Typically, a bike drivetrain system consists of two front chainrings and a rear cassette with 8 to 12 speeds. Road bikes, designed for speed and smooth riding, are equipped with larger front chainrings and smaller rear cogs than mountain bikes, allowing for faster and smoother shifting. Road bike groupsets are often made with high-end materials to ensure top performance, unlike MTB or gravel bike groupsets, which, while still performance-oriented, are usually less expensive. This is because off-road terrains expose components to impacts and scratches, making durability a key factor.
One of the most significant revolutions in road bike drivetrains has been the integration of gear shifters with brake levers. Today, this setup allows for more comfortable shifting, even when riding out of the saddle, for example, while sprinting or climbing. The shifting mechanism varies depending on the brand, but in general, the shifter functionality and the comfort of the handlebar grip are crucial for an enjoyable ride. This is why the choice of a bike drivetrain is strongly influenced by personal preference, not just performance or budget considerations.
Most drivetrain groups still use traditional rim brakes, although in recent years, disc brakes have gained popularity, especially for road and gravel bikes. Disc brakes provide stronger braking power, better modulation, and superior performance, even in challenging weather conditions. While most cyclists still opt for mechanical groupsets, electronic shifting systems have become much more than just a trend. No one knows this better than the three leading manufacturers in the global market: Shimano, SRAM, and Campagnolo.
Shimano Groupsets
Shimano groupsets are synonymous with road cycling. The Japanese brand has introduced and developed some of the most important technologies in modern cycling, many of which have become industry standards. For example, Shimano was the first company to bring the integrated "shift-brake lever" system to market, known as Shimano Total Integration (STI). This mechanism consists of a brake lever and a smaller shift lever positioned slightly behind it:
- right brake lever: pressing it shifts the chain to easier gears;
- small right shift lever: moves the chain to harder gears;
- left brake and shift levers: operate the front derailleur in a mirrored fashion.
Shimano's road bike groupsets range from the entry-level Claris to the professional Dura-Ace. The 11-speed lineup begins with Shimano 105, which offers near top-tier performance at a more affordable price. The 10-speed Tiagra is another solid choice for enthusiasts, while Ultegra is the closest thing to a high-end groupset, even in terms of design and performance.
Shimano Electronic Groupset
Di2 is the electronic version of Shimano's groupsets. Electronic shifting has been the biggest technological revolution in recent years, offering faster, more precise shifting with minimal maintenance compared to traditional drivetrains. Shimano Di2 was the first electronic groupset to enter the market successfully. As we will see later, competitors had to adapt by developing their own versions. The turning point came when professional riders started using Shimano electronic groupsets, cementing their success.
The latest Di2 versions introduced new features called Syncro Shift and Semi-Syncro Shift:
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Syncro Shift: when the chain moves to a smaller cog, Di2 automatically adjusts the front derailleur to shift to a larger chainring. This balances the gear ratio, maintaining a smooth pedaling cadence. The same happens in reverse when shifting to a larger cog. This eliminates cross-chaining and optimizes chain efficiency;
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Semi-Syncro Shift: this mode is not fully automatic. When the front derailleur is engaged, Di2 adjusts the rear derailleur to maintain a balanced gear ratio. This prevents sudden changes in resistance, making shifts smoother and more controlled, a feature appreciated even by experienced cyclists.
Riders can choose between Manual, Syncro, or Semi-Syncro modes via the Shimano app, which connects to the electronic groupset through Bluetooth, allowing further customization. All Shimano groupsets are compatible with rim brakes, and from Tiagra and above, they are also available with disc brakes.
Shimano "Hybrid" Drivetrains
Shimano also offers hybrid drivetrains, combining road and MTB technologies:
- Deore, SLX, and XT are designed for mountain biking;
- Sora, Tiagra, and Ultegra were originally developed for road bikes but are also available with flat-bar shifters;
- For city and commuter bikes, Shimano provides entry-level drivetrains like Altus, Acera, Alivio, Nexus, Alfine, and Metrea—more affordable but with less focus on high performance.
SRAM Groupsets
It may seem surprising, but SRAM has been in the road bike drivetrain market only since 2006. In the early 2000s, it entered the mountain bike market, quickly gaining success and establishing itself as Shimano’s main competitor. By 2008, SRAM had already secured professional road racing victories at the Tour of California, Giro d'Italia, and Vuelta a España.
Unlike Shimano (with STI levers) and Campagnolo (with Ergopower™), SRAM took a different approach from the start. Instead of using two levers per hand to control shifting, it developed the DoubleTap® system, which operates with a single lever under the brake:
- a short tap moves to a harder gear;
- a longer push shifts to an easier gear (activating the "second tap");
- the front derailleur operates in the same way but mirrored.
RED eTap AXS – SRAM's Wireless Groupset
To meet the demands of gravel and cyclocross, SRAM introduced the 1x (single chainring) and 2x (double chainring) options across all versions, from entry-level Apex to the top-tier RED eTap AXS. This move was inspired by mountain biking, where a single chainring setup is often sufficient for the required gear ratios. Among the three major drivetrain manufacturers, SRAM is the only one to offer three braking options:
- cable-actuated rim brakes;
- hydraulic rim brakes;
- hydraulic disc brakes.
SRAM's Response to Shimano Di2 – The Wireless Revolution
To rival Shimano Di2, SRAM developed the RED eTap AXS, a fully wireless transmission that eliminates cables while ensuring ultra-fast, precise shifting. SRAM's shifting works like a sequential gearbox in a car:
- the left lever moves to a lower gear (easier);
- the right lever shifts to a higher gear (harder);
- both levers pressed together activate the front derailleur.
Additionally, SRAM offers extra shift buttons that can be placed on the handlebar. This is especially useful for sprinters, who can shift gears without moving their hands. SRAM has also introduced semi-automatic and fully automatic shifting modes, mirroring Shimano's technology:
- Compensating Mode (similar to Shimano's Semi-Syncro Shift) balances the rear cassette when shifting the front derailleur;
- Sequential Mode (equivalent to Shimano’s Syncro Shift) automatically selects the optimal gear ratio.
SRAM eTap AXS front and rear derailleur (Photo Credit: sram.com)
Campagnolo Groupsets
The history of Campagnolo road bike groupsets dates back to the 1930s, a legacy that has led the Vicenza-based brand to produce top-tier components using high-tech materials like carbon fiber. However, Campagnolo has also developed more accessible yet high-quality products, always guided by its passion for competition. Today, all Campagnolo groupsets feature a 2x12-speed setup, except for the entry-level Centaur, which has 11 speeds. Moving up the range, we find:
- Chorus;
- Record;
- Super Record (the flagship groupset).
These models incorporate premium materials like titanium and carbon, ensuring high performance, weight savings, and an elegant design. The Super Record is specifically designed for professional cyclists.
Campagnolo Super Record EPS 2x12sp groupset available on bike-room.com
Campagnolo Shifting System & EPS Technology
Like Shimano, Campagnolo uses a dual-lever system:
- the lever near the brake shifts the chain to a lower (easier) gear;
- the thumb-operated round button moves the chain to a higher (harder) gear;
- the left-hand levers control the front derailleur.
Additionally, only the Super Record groupset features Electronic Power Shift (EPS), Campagnolo’s electronic shifting system. In recent years, Campagnolo has expanded its range to include disc brake versions for all groupsets (except Centaur). The brand also offers 140mm rotors (recommended for riders under 82 kg) and 160mm rotors for heavier riders.
Where to Find the Best Road Bike Groupsets?
Now that you have a better understanding of bike drivetrain, visit bike-room.com to find a bike equipped with the best groupsets on the market or explore the "Components & Accessories" section for a complete drivetrain upgrade. What’s that? You want to know how to install a bike drivetrain? Here you go—starting from minute 9 of this video!
