Q: The Garage Files "Poor Man's 2x10" article (August 2010) on the FSA 386
2-ring crankset has sparked an interest in looking at a 2-ring option
for my Trek Fuel EX 8. Is there any reason the new SRAM X7, X9 or X0 2-ring
cranksets would not work well with a 9-speed cassette? The SRAM cranks
state they're for use with their 10 speed cassettes, so is there a
possible compatibility issue? -Big-Ring Bud
MBA: We may have to create a special "Ask MBA Drivetrain Section" just for drivetrain
questions because let's face it, there are a lot of questions out there
on conversions and compatibility. To answer your question, Bud, as a general
rule, it is best not to mix SRAM 10-speed and 9-speed drivetrain
components. Officially they are not compatible. You could experience
reduced performance, problematic shifting, and potentially damage your
components or bike by mixing them. There are several reasons for this.
First of all, a SRAM 2x10 system uses Truvativ rings that are
specifically designed for SRAM 10-speed chain. That includes the spacing
and the design of the rings to get the shift to perform at its best.
Additionally, the front derailleur has a narrower cage design to work
with the narrower 10-speed chain.
As you move to the rear, the
cassette has also been designed to work specifically with SRAM's
10-speed chain. Keep in mind that the full benefits of the SRAM 2x10
drivetrain are achieved when using a 36-tooth large cog. This expands
the total gear range and allows you to run the big ring in a wider
variety of terrain (Big-Big is OK!). The cogs on a 10-speed cassette
are spaced slightly closer together. Obviously the rear derailleur and
shifter are also designed specifically for 10 speed.
In short, you
will not really get the full benefits of a SRAM 2x10 drivetrain without
making the full switch. The reduced weight, smooth shifts, and increased
efficiency, are achieved by using the whole system. However, one cool
benefit is the ability to mix SRAM 10-speed road and MTB components.
The SRAM Exact Actuation 10 speed allows mountain bike rear derailleurs
and cassettes to work with SRAM's 10-speed Exact Actuation shifters. But
that friends, is another story.
There are some modifications you can
make to the SRAM 2x10 mountain bike drivetrain (like the use of this
SL-700 road bike shifter), but our advice is to stick with the stock
set-up and let others do the expensive trial-and-error experiments.
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