Spin Doctor Tech Tip – 10 Speed MTB Drivetrain Compatibility

IS TEN TOO MANY?

The 2 snarling dogs of mountain bike components (SRAM and Shimano) have decided that 9 are just not enough. Yep, they are telling us that our mountain bikes need 10 gears in the back.

The first whisperings came in 2008 when bike mags and blogs hinted at the change. Late in 2009 SRAM trotted out its high-zoot XX 2×10 drivetrain. Then in 2010 SRAM expanded their 2 x10 offerings to include their X0, X9 and X7 groups.

Then the cold war turned hot! Could or would Shimano stand pat? No way, and in 2010 out comes Shimano’s 10-speed Dyna-Sys drivetrain in their top shelf XTR and XT cross country groups and in their SLX all-mountain group.

According to the early reviews these groups work great but what about compatibility? We’ll try to answer those questions but first let us introduce the new…

SRAM 2×10. The 2×10 is so-called because it pairs a double chainring crankset with a 10 speed cassette. The surprising thing about SRAM’s 2×10 drivetrains is that they have pretty much the same range of easy and hard gears as traditional 3×9 systems.

How is that possible?  First, the 10-speed cassette has an extra cog and a wider range (11-36 vs. 11-34 for the old 9-speed). And second, the double cranks have a wide jump between small and large rings.  The double is available in either a higher 28-42 or a bit lower 26-39 tooth combinations.  Traditional triples are 22-32-44.

SRAM XX 10-speed Cassette - Item #50-7639

Here’s SRAM’s take: “2X10 gives you the same amount of useable gears of a 3X9 system but with lighter weight, faster front shifting and less complexity.”  According to SRAM the 2X10 would not be possible without their new X Glide chainrings (which use a unique 4-bolt 120/80mm bolt circle diameter). These specially mated rings are sized so every tooth on the small ring lines up perfectly with a tooth on the big ring. Plus the teeth are shaped to facilitate each shift, either up or down.

SRAM XX 39/26 BB30 Crankset - Item #50-7620

The good news is that 2×10 is lighter, simpler and its shifting is synapse-quick, but there are compatibility issues. SRAM’s 10-speed drivetrain components are all cross-compatible, with a few exceptions:

1. The 2×10 drivetrains require a double left hand shifter, double crank with the X-Glide rings, 10-speed chain and double front derailleur.

SRAM XX Low Clamp Top Pull Front Derailleur - Item #50-7635 (next to old X9 triple front derailleur)

2. Their 3×10 drivetrains require a triple left hand shifter, 10-speed triple crank, 10-speed chain and triple front derailleur.

3. In a switch, SRAM’s 10-speed mountain bike derailleurs (XX, X0, X9 & X7) are now compatible with their 10-speed road shifters (Red, Force, Rival & Apex). So you can use Rival shifters with a XX rear derailleur and wide range X7 10-speed cassette for mountain centuries.

SRAM XX Rear Derailleur - Item #50-7616

4. And the bummer, their 10-speed MTB derailleurs are not compatible with their 9-speed MTB drivetrains!

SHIMANO Dyna-Sys. Shimano revamped all the key parts of their 10-speed Dyna-Sys drivetrain. They have created cassettes, front and rear derailleurs, shifters, chains and cranks that are unique and essential to the operation of the system.

The rear derailleur got a more direct cable routing (like SRAM), their shifter actuation ratio got tighter (like SRAM), their cranks got redesigned chainrings (like SRAM), their cassette got a wider range (11-36 like SRAM) and their D-S cranks are available in both 2X10 (D-S XTR only) and 3X10 (like SRAM). They also redesigned their Dyna-Sys specific asymmetrical chain (not like SRAM). The D-S chain got 4 distinctly different outer plates to speed shifting. Their triple cranks got tighter ratios (24-32-42 vs. 22-32-44) and their brand new D-S XTR double is available in multiple combinations (28-40 & 26-38 are options, with 4-bolt 88mm BCD) with ranges like SRAM.

As far as compatibility, Shimano’s Dyna-Sys products are only compatible with components in the Dyna-Sys lineup, from XTR to SLX. They are not compatible with any other parts, such as using a Dyna-Sys derailleur with 9-speed shifters.  The only part that has not changed is the front/left shifter.  It has remained the same and does not include a Dyna-Sys logo.

1. The Shimano Dyna-Sys XTR 2×10 drivetrain requires a Shimano D-S XTR left hand shifter (that is convertible for double or triple), Dyna-Sys XTR double front derailleur, D-S 10-speed chain and Shimano XTR double crank.

2. Their 3×10 drivetrains require a triple left hand shifter, 10-speed D-S triple crank, 10-speed D-S chain and Shimano D-S triple front derailleur.

3. In a switch, Shimano’s D-S 10 speed rear derailleurs (XTR, XT and SLX) are NOT compatible with Shimano road shifters nor with other non-D-S MTB shifters.

We hope that this clears up some of the questions you’ve got about these new 10-speed mountain bike components, but if you need more help be sure to give Spin Doctor Product Services a call; they’ll be happy to help!

You can find all of our 10-speed mountain bike components in one handy group here.