Each season, bicycle manufacturers introduce new features to the market to update and improve their models. These changes can be a new frame geometry, lighter materials, or different assembly and components. Within the world of the mountain bike
the latest trends have focused on the drivetrain. In five or six years, we have gone from using three chainrings to having the possibility of mounting a single chainring. The single chainring is a trend that is gaining great momentum and more and more bikers are opting for a mountain bike with just one chainring. But what are the advantages and disadvantages of single-chainring drivetrains? Is it just a matter of fashion or is there more to it? Below, we analyze the pros and cons of choosing single-chainring mountain bikes.
Up to 800 grams less weight
The battle against the scale drives many of the innovations applied to bicycles. By using a single chainring, we are getting rid of a shifter, cable and housing, the front derailleur, and one or two chainrings. In addition, the chain used is shorter than those of double or triple chainring setups; and since, for now, the single chainring is used in high-end groups superior, the materials used for chainring, cassette, and chain are lighter. Among all the parts we are removing from the bike, we can save between 500 and 800 grams.
Smoother shifting
Probably the greatest advantage of the single chainring is its simplicity, even above weight. Using just one chainring eliminates, above all, the choice of which gear ratio to use depending on the terrain. This directly influences the fact that we forget about chain suck. It has happened to all of us that while descending a trail or path, we suddenly encounter a small but steep climb, and we get stuck. We have to shift up on the cassette while shifting down on the chainring, and in that operation, the chain comes off. With the single chainring, we simply have to shift up on the cassette (in some shifters, you can shift up to five gears with a single push) and keep pedaling. In addition, the single chainring drivetrain provides a greater sense of smoothness and a finer, softer feel. This is due, among other things, to the much more centered position of the chainring relative to the cassette cogs, which reduces chain cross-chaining.
No overlapping gears
A priori, when we compare a single chainring drivetrain with conventional two or even three chainring setups, we find fewer gear options. Multi-chainring setups offer up to thirty possible combinations of chainrings and cogs. With single chainring setups, we can only use a maximum of 12 speeds. Having between 9 and 19 fewer gears may seem like a drawback, but the reality of two and three chainring groups is different from the theory. Those who still use three chainring groups know that many of their combinations overlap, and that using the large chainring with the fourth cog is basically the same as using the middle chainring with the second cog. Also, to avoid cross-chaining and drivetrain wear, there are a series of 'forbidden' combinations, limiting the small chainring to the top 4 or 5 cogs, the large chainring to the bottom 4 or 5, and the middle chainring to all but the last few at each end. When we eliminate duplicate and not recommended gears, we realize that, out of the 30 available, only about half are actually recommended for use. On single chainring bikes, however, because the chainring is more centered relative to the cassette, it is possible to use all the speeds available on the drivetrain.
Possibility of swapping chainrings
Partly to adapt single chainring setups to most users, and partly to cover different gear needs according to various types of terrain, you can find chainrings in different sizes, making it possible to swap them. While three-chainring drivetrains used to come standardized with a 44/32/22 and double chainrings with 40/28 teeth, and changing these setups was rather cumbersome, with single chainring setups it is quite easy and quick to swap a smaller chainring for a larger one. You won’t need the same chainring to cross the plains of Castile as you would to climb the Cantabrian coast, and even though the latest SRAM models require some adapters and intermediate parts to swap them, the option to change them still exists.
Popeye’s spinach
As for the drawbacks of bikes with single chainring drivetrains, perhaps the main one is that they are not suitable for everyone. In some cases, the eleven or twelve gears found on single chainring setups may fall short for a large number of bikers. Saving half a kilo of weight on the bike may be of little use if our legs are not capable of moving the gears we have.
One chainring to not rule them all
With a single-chainring mountain bike, it is difficult to find a chainring that will give us optimal gear ratios throughout all our rides. If we use a smaller chainring like a 30, we can enjoy easier climbs, but as soon as the terrain becomes favorable, with a cadence of 90 pedal strokes and an 11-tooth cog, we will barely reach 34 km/h, soon running out of the ability to contribute anything with our pedaling. On the other hand, if we use a 34-tooth chainring, we can reach up to 38 km/h on flat terrain, but it is very likely that if our physical condition is not high, we will be left struggling on the first steep ramps. And what does this tell us? If you like riding on trails or even roads, you may not find a gear ratio that lets you take advantage of descents without sacrificing climbs, and vice versa. If you like climbing on trails and descending on singletracks and technical routes, it may not matter as much. The good news is that both SRAM and Shimano are working hard on cog sizes, and while the Japanese are close to releasing a 50-tooth cog that would allow us to use slightly larger chainrings and still climb easily, SRAM, for its part, has the twelve-speed cassette ready, in addition to its patented ten-tooth cog that gives a huge boost on flat terrain.
Fewer chainrings, but more expensive
Single-chainring groups are at the forefront of technology, becoming high-end components. This means that bikes with this type of drivetrain are not within everyone's reach. Shimano has the cheapest groups, but, promotions aside, you have to spend around 500 euros to get an 11-speed XT group, with the XTR reaching 800 euros. SRAM starts with its NX group from 320 euros, and surpasses one thousand euros with the Total SRAM XX1. In addition, the components are also somewhat expensive, with chainrings ranging between €60 and over €100.
The single chainring is here to stay
mainly aimed at more competitive users, but without losing sight of more relaxed users, which is where the industry seems to be heading. We assume that the greater its acceptance in the market, the more its price will become popularized, but this depends on managing to find wider gear ratios for all audiences. Who knows, maybe before long, the triple chainring will sound as outdated to us as velocipedes do today—Jurassic technology.