31 March 2010

bikefix Initial Review: FSA K-Force Light 2x9 MegaExo crankset

About a year ago I decided to try a 2x9 set-up on one of my lighter, racier bikes, figuring that it might be fun and beneficial to push a higher gear on the granny climbs. FSA had recently released their K-Force Light cranks in a 2x9 configuration, which were hollow monocoque carbon arms with a ceramic bottom bracket- so I was sold. More than just forcing me to push a bit harder, I was also intrigued to see if the 2x9 setup's shifting would be crisper and if the drive-train would be less prone to troubles or “de-tuning.”

On the trail, the first thing I noticed was that I often had no idea what gear I was in. Normally, I think that I subconsciously know what gears I use on which climbs, but the mental translation to 2x9 threw me off a bit. After a few rides though, the mental adjustment was complete, and I could focus on the shifting. Strangely, the shifting wasn’t that much better than on 3x9 systems. The rear shifting felt the same, and front shifts were only marginally better. When “gunked-up” with mud, though, the front still felt pretty good, which is not always the case with a triple up front. Also, shifting the front under power is better than on a 3x9, but we all know that shifting under torque is a “no no” and should be used as a last resort. The cranks are available in either a 44/29, or a 42/29 chainring combination. I chose the 42/29 matched with a standard Shimano 11-34 cassette, and it is fantastically livable for most trail riding, the one exception being long climbs at altitude. I found myself wishing for a bit more granny-gear after a mile or two in the thin air. Those of you who weigh less than my 195 lbs. might be more immune to this problem though, and the emergence of 36 tooth cassettes from SRAM and Shimano could make the 2x9 viable for all but the highest and nastiest climbs. The chain line is straighter with a 2x9 of course, and this makes things more efficient and more pleasant by reducing chain rub and noise.

The FSA ceramic bottom bracket that comes with the K-Force Light crankset is one of the best in the business. After owning a few different manufacturers’ ceramic BB’s, I can say with certainty that the FSA lasts the longest and still turns amazingly well. That being said, I’ve never physically noticed any performance difference from using a ceramic bottom bracket over a regular one.

The K-Force cranks are handsome too, with a neat red & white color scheme over the carbon weave. Being carbon, they are light (at a claimed 733g) but still similar in weight to XTR cranks when all is said and done (796g actual, despite having one more chainring). They also feel stiff, but not noticeably more so than other high end cranks that I’ve ridden. The FSA's can take a beating though- that I know. They are mounted on a bike with a very low bottom bracket and I am always bashing these arms into rocks. So far I’ve had no problems other than cosmetic damage.

In the end, these cranks are a legitimate set-up for almost anybody who wants to simplify their drivetrain. They are also a nice way to encourage the rider to turn slightly higher gears than they are used to. This will likely make your bike feel a bit different- and that can be a positive thing. FSA also has a similar 2x9 crank with a slightly more usable 27 tooth small chainring. This crankset is called the “K-Force light 386” but has a proprietary chainring bolt pattern which limits your options/usability with that model. FSA has a well made high end product in the K-Force Light 2x9’s. They retail for a not cheap $770.00, but a less pricy (and heavier) alloy version is available.



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