Shimano or SRAM? The battle for cycling transmissions
If we talk about mountain bike groupsets, Shimano and SRAM have historically been the two main contenders, each with technology the other couldn't match. Until now, Shimano dominated the market with its electronic Di2 shifters, while SRAM offered the exclusive 12-speed cassettes in its Eagle transmissions. However, this advantage is about to disappear.
It seems that SRAM will soon present its new wireless Eagle eTap, designed to compete directly with Shimano Di2 electronic systems. In fact, Nino Schurter, one of the great MTB stars, has already tested this revolutionary technology. For its part, Shimano has just unveiled its new Shimano XTR range, whose main innovation is the introduction of a 12-speed cassette, thus matching its offer to that of its main competitor.
Since its launch in 2016, the SRAM XX1, X01, and GX Eagle groupsets marked a before and after in the development of transmissions for mountain bikes, by introducing the first 12-speed cassette. This breakthrough consolidated single chainring systems, which have been gaining popularity over the traditional double chainring, optimizing efficiency on technical terrain and increasing maintenance simplicity.
Meanwhile, the future of the Shimano XTR 12v will not only influence the MTB world, but could also set the path for its equivalent in road bikes, with a possible evolution of the Dura-Ace 12v group, which would compete with the 2x12 options recently introduced by Campagnolo. Innovation in transmissions does not stop, and both mountain and road cyclists can expect great advances in the coming years.
"The new Shimano XTR 12-speed groupset for cross country and enduro is a preview of what the future Dura-Ace 12-speed road cycling groupset could be"
This Eagle range from SRAM marked the definitive springboard for the rise of single chainring transmission systems. Although double chainring systems remain the most common standard, the truth is that the single chainring has been gaining followers ever since SRAM's eye-catching 12-speed cassette with its impressive superior 50-tooth cog made its debut. Since then, everyone has been waiting for Shimano’s response. Loyal fans of the Japanese manufacturer, especially those who were becoming attracted to single chainring transmissions, were demanding a bold move from Shimano to allow them to switch from 1x11 to 1x12 without having to change sides and use SRAM transmissions. Some media even went so far as to publish that Shimano was preparing to launch a 13-speed groupset! It was called the Shimano XTR Fisherman 13-speed and was supposedly going to feature a 55-tooth cog. However, this turned out to be nothing more than an April Fools’ joke (though many believed it was real). More than two years after SRAM broke the 11-speed ceiling for mountain bike cassettes, Shimano has finally launched its 12-speed groupset. What can you expect from it?
Shimano XTR M9100 and M9120 12-speed
The new Shimano XTR 12-speed groupset for mountain bikes is not only the Japanese manufacturer’s answer to the SRAM XX1 Eagle. It also anticipates what the future Dura-Ace 12-speed groupset could be, with which Shimano will compete against the 2x12 group recently launched by Campagnolo for its Record and Super Record ranges. In reality, what Shimano has brought to market is not just a new groupset for its XTR range, but two. Each one is designed for a different type of use. On one hand, we have the Shimano XTR M9100, with specifications for cross country. On the other, the Shimano XTR M9120, designed for the enduro segment. These are two clearly differentiated formats, intended to meet different needs in the world of high-level competition. For example, one of the new features introduced by Shimano is four-piston brakes for its enduro version and a more durable chain. You can also choose different gears and transmission ratios, with both single and double chainring systems. However, the main innovation is the possibility of fitting a 12-speed cassette.
Technical innovations beyond 12-speed
The new Shimano XTR 12-speed derailleur is more than just an extra cog on the cassette to compete with SRAM's Eagle groups. In fact, if the only reason to want it is the 12 speeds on the rear derailleur, there are few differences compared to SRAM's XX1. Other technical innovations introduced by the Japanese manufacturer are much more interesting, such as a remote lever for a dropper post. This feature, which may seem trivial to most bikers, can make a big difference for those competing in enduro events.
"This is not a range update, but an entirely new group"
Another improvement over previous XTR ranges is the brakes. In fact, this was one of the main criticisms Shimano received. The most demanding riders could not understand how the XTR groups had a braking system more typical of lower-end ranges than what should be the top-of-the-line group for a brand like Shimano. This new XTR 12-speed group features two completely new brake models, with 2 and 4 pistons, with 10% less lever travel, which improves actuation without having to squeeze hard.
Direct mount cranks
Another innovation is in the cranks. Initially, since the new XTR group is designed for high-level competition, one might expect Shimano's approach to weight reduction to involve using carbon as the material for making the chainrings and cranks. Instead, the Japanese have chosen to go with a direct mount system. That is, the chainring is mounted directly onto the crank arm base without the need for a spider for attachment. Shimano thus follows in the footsteps of manufacturers like Specialized or Cannondale who already opted for these direct mount systems in their day. In this way, Shimano claims to have reduced the overall weight by 80 grams. Its weight is 511 grams for the 30D single chainring version and 592 grams for the M9100 double chainring version. Although the group has been developed for 1x12 drivetrains, it also supports double chainring setups. The single chainring setup of the new Shimano XTR 12-speed group has 5 different chainring options: 30, 32, 34, 36, and 38 teeth. The double chainring version, meanwhile, comes with a 38-tooth superior chainring and a smaller 28-tooth one.
Steel, aluminum, and titanium
As already mentioned, the cassette is the main innovation brought by the new Shimano XTR group. But not just because of the obvious jump to 12 cogs, but also due to differences in stiffness and weight compared to the XTR HG-9001 11-40T cassette. Regarding the first of these aspects, the new sprocket set is 30% stiffer, thanks to the combination of materials used by Shimano's engineers: titanium, aluminum, and steel.
"DT Swiss is the only manufacturer licensed to make wheels compatible with the new XTR 12-speed cassette"
The four smallest cogs, which are the ones that suffer the most wear, are made of steel. The three largest ones are made of aluminum. The rest are made from an aluminum and titanium alloy. The result is an impressive weight of just 359 grams for the 10-51 development version and 349 grams for the 10-45 version. As a reference, the weight of an XX1 Eagle 12-speed cassette is 360 grams (and all but one of the sprockets are steel). According to Shimano, this combination of materials provides greater rigidity and durability to the cassette.
Differences with SRAM Eagle
There are three gearing options for the rear derailleur, each for a specific type of use:
- Shimano XTR 12-speed 10-51: 10t-12t-14t-16t-18t-21t-24t-28t-33t-39t-45t-51t
- Shimano XTR 12-speed 10-45: 10t-12t-14t-16t-18t-21t-24t-28t-32t-36t-40t-45t
- Shimano XTR 11-speed 10-40: 10t-12t-14t-16t-18t-21t-24t-28t-32t-36t-40t
All three range options include a 10-tooth cog as the smallest sprocket. In this aspect, Shimano matches SRAM. As for the largest cog, the Japanese manufacturer goes for an impressive 51-tooth sprocket. That’s just 1 more than SRAM’s (50). The big difference comes in how the gear jumps are arranged up to the largest cog. The SRAM 12-speed Eagle cassette has an 8-tooth jump in its last 2 sprockets (10t-12t-14t-16t-18t-21t-24t-28t-32t-36t-42t-50t). Shimano, on the other hand, has opted for more gradual gear jumps, making a difference in the last four cogs. For bikers who practice enduro or high-elevation marathon, this wider and more gradual range that Shimano offers in the largest sprockets can provide an advantage for finding a more comfortable gear without having to make as big a jump as SRAM proposes.
Incompatibilities
If your mountain bike already has a Shimano XTR 11-speed derailleur and you intend to switch to 12-speed, there’s bad news: simply buying the cassette won’t help you. The new Shimano XTR 12-speed group is incompatible with previous generations.
"Shimano seems to be definitely going after the single-chainring drivetrain market in mountain biking"
This is not a range update, but a completely new group. For practical purposes, the only compatible element between your current drivetrain and the new one will be the wiring. The new 12-speed cassette is also not compatible with just any wheel model. In fact, it is not even compatible with other Shimano freehubs except for the specific one for the new XTR range. The Japanese manufacturer has patented a new freehub that incorporates a micro-gear system called Hyperglide+. The good news is that this system provides smoother shifting and allows you to keep pedaling while changing to a gear superior or lower. On the other hand, mechanically it is very different from the Hyperglide standard that Shimano had been using until now, to the point that you cannot mount the XTR 12-speed cassette (nor the 11-speed from the same range) on a freehub from the previous XTR range. So far, the only wheel manufacturer licensed to use the new Shimano XTR 12-speed freehub standard is DT Swiss. In summary, even though it is two years late, Shimano seems to be finally going after the single chainring drivetrain market in mountain biking. And it does so with a completely new group that not only anticipates the new top-tier drivetrain scenario for cross country and marathon, but also hints at what may be the Japanese manufacturer's next move for road cycling: the 12-speed electronic shifting.