Over the past six years, the compact double crank has completely replaced the triple crank in road bikes. The reason is simple: when paired with a standard 10-speed cogset, a compact crank provides nearly the same range of available (and some would argue more usable) gears as a triple, but with less weight and less shifting failure points. Why churn through three rings on the front (where most problems are prone to happen since that’s where the chain is under constant tension), when you can access an optimal range of gears with just two rings? The answer was obvious, at least to roadies. But the U.S. mountain biking industry remains split down the middle on the topic.

The reigning king of the drivetrain, Shimano, and the crown prince, SRAM, have taken opposite sides. Both jumped on the 10-speed bandwagon for mountain bikes this year, employing wider cogsets (11-36). But Shimano revised the chainring sizing and spacing on their triple crank, for what they’re calling a “trail tuned” triple, while SRAM took it’s cue from road biking and did a way with triples altogether, opting instead for a trail compact crank that they call “2X10.”

So should you run a triple or double on your mountain bike? Shimano or SRAM? Let’s take a closer look:

Three Times as Fun (The Shimano Dyna-Sys Drivetrain)
In order to pair with the wider 10-speed cogset in the back, Shimano revamped their front gearing for optimal efficiency. They created a more narrowly spaced triple crank: the small chainring is bigger (24 teeth instead of 22), the middle ring is the same (32 teeth), and the big ring is smaller (42 teeth instead of 44). The end result of this re-jiggering is smoother and more intuitive shifting. Plus, Shimano claims that chain tension is reduced in certain gear combinations by more than 30 percent, mainly because the new configuration permits a wider range of effective gearing from the middle 32-tooth ring (think 32 chainring/36 cog instead of the equivalent 22/25).

Less is More (The SRAM 2X10 Drivetrain)
SRAM couldn’t agree less with Shimano. The 2X10, a 42-28 double crank, is at the heart (and in the name) of their newest drivetrain resulting in a lighter, faster, and more responsive bike. SRAM so firmly believes that a full gear range can be achieved with fewer front gears that XX, their premier mountain bike group is only available with a 2X10 crank. Technically, the one thing you lose going from a triple to a double is the granny gear, the easiest of easy gears. The flagship XO groupset, and the next-best thing, the X9, are nearly all 2X10, but still come with a triple option. The X7, their entry-level group, is the only one regularly sporting triples, as brand newbies are about the only ones who need the granny.

SRAM admits that the weight shaved by going from a triple to a double is minimal (less than 100-grams). The real benefit is increased performance (as in lightning-fast shifting) and less failure points in your shifting. The 2X10 also has a three-to-two ratio of large ring to small ring teeth, creating 14 perfectly timed shift locations. That’s a substantial advancement in chainring geometry that should replace the typical slop between gears with a crisp, clean, immediate shift.

Survey Says!
We talked to James Huang, the technical editor at CyclingNews.com, to get some unbiased feedback on Shimano’s and SRAM’s competing approaches. “Ultimately, it's not a matter of one being better than the other,” Huang said. “It’s more a matter of preference. If you’re new to mountain biking or going to be touring and carrying a heavy load, having that granny gear provided by a triple may be really important.”

We couldn’t get Huang to fess up to one being better than the other, but we could clearly see that he was sporting SRAM 2X10 on his own mountain bike. Clearly he is neither new, nor touring.

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