To answer these questions, it is best to know what you are talking about and what are the main characteristics of the groupsets offered by manufacturers.
We can start focusing on weight and smooth shifting, racing bike groupsets are built made of a variety of materials, even some sophisticated ones, to achieve high performance. The drivetrain usually consists of two front chainrings and an 8-12 speed cassette. Because of their smoothness and speed, road bikes, are assembled with larger front sprockets and smaller rear sprockets than mountain bikes. Due to the smaller range, this allows smoother and more fluid shifting.
The most significant revolution in the world of road bike groupsets involved the gear levers position. They are now integrated with the brake levers and allow a much more comfortable shifting, even when the rider is standing on the pedals. The functioning of the shift levers, as we will see later, varies with each manufacturer.
This is what drives enthusiasts’ choices: the way the gear levers work and the comfortable handlebar grip are fundamental for enjoyable cycling. Choosing a drivetrain is therefore greatly influenced by personal preferences and taste, and not only by economic and performance reasons. Every cyclist has his or her own preferred manufacturer.
Most groupsets still feature traditional brakes, although disc brakes have become more and more popular in recent years. This is due to their being more powerful at braking, better modulated, and better performing even in less than optimal weather conditions.
Although most riders still choose traditional mechanical groupsets, electronic ones are getting more and more in fashion. Shimano, SRAM, and Campagnolo all offer several models in electronic versions.
Shimano
Shimano is synonymous with racing bicycles. It has introduced and developed some of the most important technologies in cycling today, many of which are now considered a standard. For example, Shimano was the first to introduce the integrated shift levers and brakes we are familiar with today. It was called the “Shimano Total Integration” or “STI”. This mechanism consists of a brake lever and a second, smaller shifting lever behind it. The chain switches to more agile ratios when the right brake lever is pushed; if you move the smaller lever instead, the chain drops to a harder ratio. The left levers work according to the same principle, but symmetrically, and operate the derailleur work.
Shimano road groupsets range from the entry-level Claris, all the way up to the professional Dura-ace. The 11 speeds start with Shimano 105, which is almost as performing as a top-of-the-line groupset at a significantly more affordable price. Even Tiagra’s 10 speeds offer a solid solution for enthusiasts. Ultegra, on the other hand, is as close to a top-of-the-line groupset as it gets, also in its design.
Di2 is the electronic version of Shimano groupsets. Electronic shifting represents the most important technological revolution of recent years. Compared to the traditional transmission, there is undoubtedly an improvement in shifting, which is faster and more precise with almost no need for maintenance. Di2 was the first electronic transmission to successfully enter the market. Competitors then had to adapt by developing their own versions, as we will see later. A few years ago the professionals began to use Shimano electronic groupsets, thus consecrating its success.
The latest versions of Di2 witnessed the introduction of some new features called Syncro (and Semi-Syncro) Shift. In the fully Syncro version, when the chain is shifted to the smaller sprockets, Di2 intervenes automatically and shifts the rear derailleur to the larger front sprocket. Then, it balances the rear sprockets to maintain the same metric development and avoid hindering pedaling fluidity. In the same way, but in the opposite direction, Di2 automatically intervenes to shift the rear derailleur to the smallest sprocket when the chain moves up to the highest sprockets.
The electronic transmission allows the chain to always work in an optimal way, eliminating so-called chain crossings. The Semi-Syncro mode, on the other hand, is not fully automatic. When the derailleur is operated to change from one chainring to another, Di2 intervenes in the positioning of the chain in the rear sprockets, rebalancing them to ensure smoother and less impactful shifting. This prevents you from feeling too agile or too hard when shifting from one front sprocket to another, a feature that can be appreciated by even the most experienced cyclists. You can select Manual, Semi-Syncro, or Syncro modus directly from the control unit or from compatible apps, connected via Bluetooth, which also allows you to customize other settings.
All versions of Shimano groupsets are compatible with traditional brakes, and you can have the disc brakes version on from Tiagra upwards.
Shimano also offers a series of so-called hybrid drivetrains. These are a mix of those designed for the road and those designed for mountain biking. Deore, SLX, and XT are made for MTB while Sora, Tiagra, and Ultegra, although they were originally developed for road bikes, are also available with levers that were specifically designed for flat handlebars. Finally, Shimano offers several low-end drivetrains which are ideal for city bikes. We are talking about Altus, Acera, Alivio, Nexus, Alfine, Metrea, and other models, which are not as expensive, but also not quite as performing.
SRAM
It may sound incredible, but SRAM has only been on the road drivetrain market since 2006. At the beginning of the 2000s they entered the mountain bike drivetrain market and immediately became very successful, establishing themselves as the main competitor to Japanese Shimano. In 2008, only two years later, they even had their first victories among the professionals of road bikes at the Tour of California, the Giro d’Italia, and the Vuelta an España.
Unlike Shimano with its STI levers and Campagnolo with its ErgopowerTM, SRAM immediately tried a different approach. Instead of using two levers on each hand to control the shifting, the DoubleTap® system uses a single lever located under the brake to affect shifting. To move the chain down to a harder gear, a single, shorter tap is sufficient; to shift it up to a more agile gear, on the other hand, you have to push the lever harder, activating the so-called second tap. The same method, but in a specular way, is used to activate the front derailleur.
To meet the needs of “hybrid” riders, gravel, and cyclocross, SRAM, decided to offer the 1x (front single chainring) or 2x (front double chainring) variant for all versions, from the entry-level Apex to the top of the range RED® eTap AXS. This move was inspired by mountain bikes. For cyclocrossers in particular, the single chainring is definitely enough to develop the necessary ratios. Among the three major manufacturers, SRAM is the only one to supply brakes in three different options: traditional cable-operated rim brakes, hydraulic rim brakes, and hydraulic disc brakes.
In response to Shimano’s electronic Di2, SRAM developed an innovative RED® eTap AXS. Eliminating the need for cables or wires, eTap AXS is an entirely wireless transmission system that allows fast and highly precise shifting. The levers of the SRAM RED® eTap work like the sequential shifters in a car: the left lever raises the chain to a more agile ratio, and the right lever drops the chain to a harder ratio. To operate the front derailleur, however, you have to push both levers at the same time. With SRAM it is also possible to insert one or more buttons to operate the rear derailleur without using the levers. The button located on the lower, curved part of the handlebars can be, for example, very useful for sprinters who are launching a sprint. Thanks to this feature, they don’t have to move their hand to change gears.
Just like Shimano, SRAM too introduced the possibility of a semi-automatic version, the Compensating (which works like Shimano’s Semi-Syncro), and an automatic version, the Sequential (corresponding to Shimano’s Syncro).
Campagnolo
Campagnolo road groupsets combine style and performance with a long history in road racing. Campagnolo has been associated with the highest level of road racing since 1933. Campagnolo has always had an eye for high-tech materials such as carbon fiber, and it shows in its drivetrains. Since Campagnolo is a racing brand, its lowest-quality product range is medium level. After all, their target is a competition-oriented group of customers. Campagnolo is what the British would call a “heart over head brand”, where passion is the master and dictates the company’s guidelines.
All Campagnolo groupsets today feature a 2×12 speed, except for the reintroduced entry-level Centaur, which features 11 speeds. On the way to the top, we can find Chorus, followed by Record and Super Record. These models are made of high-level materials such as titanium and carbon to guarantee high performance while sparing some weight of the groupset, as well as making it more attractive. The top-of-the-range Super Record is designed for exclusive bicycles: those used by professional riders.
Campagnolo, like Shimano, uses a two-level system. The one located near the brake is used to move the chain up to a more agile ratio; while the round lever, operated with the thumb, moves the chain down to a harder ratio. As always, the levers on the left operate the front derailleur. The Electronic Power Shift, or EPS, is Campagnolo’s electronic system and can be found exclusively on the Super Record EPS groupset. Like Shimano’s Di2 system, EPS also needs a few cables to transmit the shifting.
Campagnolo recently started releasing disc brake versions of its groupsets (available for every model except for Centaur). Campagnolo was the last big brand in doing so. It also offers the option of fitting 140mm rotating discs, recommended for cyclists who weigh less than 82kg, or 160mm for everyone else.
Now that you know more about the main features of the bike groupset, it’s time to choose!
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