Our readers are asking: How the heck do I get power measurement on my tracklocross rig?
Ah, what tracklocross racer hasn't secretly lusted for power data? You know you're throwing down HELLA watts, but how many exactly? Is it the difficult conditions today or do I suck? (it's the headwind). Well now, courtesy of our friends at RaceFace, we have a solution. Enter the Cinch spindle-based power meter.
RaceFace was kind enough to make their Cinch BB system compatible with pretty much everything -- including track bikes with 68mm British-threaded bottom brackets. Woohoo!
Unfortunately, you will need a special tool, which can be had from RaceFace (via Amazon) or Park. The Cinch BB system uses a 12-spline interface and nothing in my tool drawer would fit. Kind of a drag but the tool isn't expensive at least. Your LBS probably won't have it.
Of course, you will need a suitable chain-whip tool and lock-ring tool. If you are running a 1/8" chain, you'll need one like this Park SR-18.2. If you're running 3/32" (road standard), you'll need a different one (and a suitable cog for said chain).
Here's the crank and BB all installed. With this spindle (134mm), RaceFace includes 3 spacers which you can arrange to suit your needs. In the instructions they say to put two on the drive side and one on the non-drive side. I did the opposite for chainline reasons, which helped. I also put a spacer (from a Campy-10 cassette) behind the cog to space it out a little. The chainline isn't perfect, but it's pretty good and runs almost silently.
Here's the bike all finished. For tracklocross, a ~2.35 ratio is pretty ideal, assuming a fairly flat course. This bike has a 36t chainring and a 15t cog, which yields a 2.4 ratio. A note on the chainring: this is RaceFace's very cool narrow-wide direct-mount type, which means you're very unlikely to drop a chain and also that you can only get chainrings in even tooth increments. These things seem to work great with either a 3/32" chain or a 1/8" chain. Some purists might not like it, but I'm running a 1/8" and it works like a champ.
Note that Easton (corporate sibling of RaceFace) sells a road version of the Cinch power meter, which is a 129mm spindle. That's what I probably should have used, but the mtb version is what I had on hand. Next time.
Race tracklocross in San Diego with fiestaislandcx.com or with Resistance Racing in the SF Bay Area