SRAM XX1 Drivetrain

Specs: 2013 SRAM XX1 Group (shifter, derailleur, crankset, cassette, chain)

Bike Setup: Black Market Roam, 160mm Travel, Enve AM wheelset, Saint 203mm Brakes

Days Tested: 30 rides, 60+ hours

Test Locations: Pedal and shuttle-access trails, Salt Lake metro area, Utah.

The new SRAM XX1 group is, I believe, the first complete group specifically designed from the ground up for single front ring use on a mountain bike. Previous single-ring groups such as SRAM XO DH and Shimano Saint incorporated road cassettes and short derailleur cage lengths, rather than being purpose built for the application.

While some components in the XX1 group (e.g., the shifter, crank-arms, and chain) are incremental updates to the existing SRAM XX 10 speed group, several key components have been designed specifically for the purpose of single-ring use. The cassette features a far larger range (10-42 vs. 11-36) in its gearing, and it affixes to the hub in a new manner to accommodate the 10t cog. The derailleur moves in a linear manner rather than diagonally, as previous rear derailleurs have. And the chainring uses an alternating wide-narrow tooth design to better retain the chain.

Why Go 1 x 11?

The biggest selling point of the XX1 group, and its push into 11-speed territory, is to offer an adequate gear range in the single-ring format for most users.

I don’t think anyone who rides bikes a lot particularly likes front derailleurs—they are noisy, they rapidly lose their shifting precision as the chainrings wear, and they frequently drop the chain when riding through rough sections of trail. The additional gear range that a front derailleur provides on trail bikes is really the only reason to run multiple chain rings.

Long story short, modern 5-6” bikes have become so light and capable that a better option became obvious: marry wide-range rear cassettes to single front rings. The result is better chain retention at speed through rough terrain, a quieter ride, and less maintenance. And the explosion of popularity over the past two seasons with folks running single-ring setups paired to 11-36t / 10-speed cassette illustrates the demand for this simplicity.

However, many users of 10-speed single rings have longed for a bit more range, finding that the 11-36 cassette range either sacrifices a bit going up (“I wish I had just one more shift”), or sacrifices a bit going down, especially on a long paved road exit to the car. And on many rides, the longing is for one more shift while climbing, and one to two more shifts while descending.

Sram XX1 Gearing Overview

The XX1 can be set up using any one of six big rings, ranging in even multiples from 28t to 38t. So a quick breakdown on how the gearing of the XX1 works relative to a few conventional setups is a good place to start. For the sake of this review, those will be:

• a conventional 9-speed, 24-32-44 front / 11-32t cassette
• a 22-32-44 front / 11-34t cassette micro triple gear range, and
• a 10-speed, single 32t front / 11-36t cassette arrangement.

With a triple crank, you generally would use:

a) the 2-3 largest cassette cogs with the granny ring
b) the 2-3 smallest cassette cogs with the big front ring
c) the entire cassette with the middle ring, since all the other gearing options overlap and are superfluous.

With a single-ring setup, you use every single gear in the range, and don’t have to lug around overlap material.

With that in mind, the easiest way to compare drivetrains is to look at their highest and lowest available gearing. And for the sake of simplicity, the descriptions of the gear ratios that follow are defined as such: if a gear is less than 1.5% different, I will refer to it as being “equivalent.” Jumps in shifting on most clusters are on the order of 5%, and that is what I refer to as “one shift.”

Sram XX1 Relative to Triple Setups

Low End:

The XX1 with a stock 32t chainring (the middle of the six available sizes) and the 42t big cog in the rear yields a gear ratio similar to a 24t chainring (granny ring) and a 32t cassette cog on a 9-speed setup. The XX1 is just one shift short of a micro-triple gearing—22t chainring and 34t cassette—of the widest triple range out there.

High End:

The same XX1 32t chainring mated to the 10t small cog yields a gear ratio equivalent to the 44t chainring paired to a 13t cog – 2 clicks up from the tallest 11t cog on the cassette.

This XX1 arrangement therefore offers the same range of a conventional triple crank setup, minus a total of two shifts from a traditional triple gearing and three shifts compared to a micro setup.

By changing the front chainring, you could set up the XX1 to give up the micro’s low-end hill-climbing ability (relative to the 22t chainring / 34t cog setup) by going to the smallest 28t chainring. Doing so would cost you three shifts on the top end.

XX1 Relative to a 10-speed Single Ring

The XX1’s 10-42 cassette is obviously going to offer a wider range than a 10-speed 11-36 cassette, but the questions are (#1) “How much wider?” and (#2) “Which gearing (i.e. chainring) should I select?”

High End:

• The 32t chainring mated to the XX1’s largest 42t cog is the equivalent of two shifts lower/easier than a 32t chainring mated to a 10-speed’s largest 36t cassette cog.

• The 34t XX1 chainring mated to the 42t cog is the equivalent of being one shift lower/easier than the 10-speed’s 36t cog.

• The 36t XX1 chainring mated to the 42t cog is about the same (a half shift lower/easier) than a 32t / 36 cog arrangement.

Low End:

• The XX1 32t / 10t cog arrangement is one gear higher/harder of a gear than a 32t / 11t cog pairing.

• The XX1 34t / 10t cog is about 1.5 shifts higher/harder.

• The XX1 36t / 10t cog is two shifts higher/harder.

So, What Size Ring – 32, 34, or 36?

So if you are currently running a 10-speed single-ring setup and wish to go to an 11-speed for an increased range, figuring out the gear range you want is really pretty straightforward. If you are coming off a fairly standard 32t front ring, then the questions are:

a) Do you want to keep the same gearing when climbing, but add a higher end for going downhill? Go with 36t.

b) Do you want one shift more while climbing and one more shift while descending? Go with 34t.

c) Do you simply want more help on climbs, and don’t need a bigger gear for going down? You can add two more shifts for climbing by going with 32t.

What I Chose

I have ridden a 10-speed, 32t / 11-36 setup exclusively for the last two seasons, and while there were a number of climbs where I would have loved to have one more shift, I didn’t really ever need it … but I did have to force my way through a chunk of hill on a number of climbs, grinding it out to the top.

On the XX1, I have experimented with various chainrings, but have settled on the 34t, though I will occasionally switch to a 36t if I’m going on a ride that has a long road section back to the car.

The 32t was really nice to have on my XX1 at the start of the season, but with mid-season fitness coming on, I don’t really feel the need for the easier gearing, and I really appreciate the top speed. But having the one additional bail-out gear with the 34t / 42t ratio is still much appreciated from time to time.

NEXT: A Look at Each Individual Component