Originally Posted by
carleton
If you are building a system for your son to use for several years, invest in an SRM kit. It's worth it in the short term and especially in the long term.
You can buy alternate crank arms with different lengths for the SRM track crankset for $200/pair. I'd imagine that as an aspiring pursuiter, he will be experimenting with crank lengths as well as other parts of the bike. To put that into perspective, a new set of Dura Ace crank arms costs $400-450/set.
You change the drive-side crank arm by using a star nut wrench and remove the crank arm from the power meter spider. You will then have to recalibrate it. It's not hard. I've done it in my living room. Or you can simply mail it in to SRM and have them do it. Let left side crank arm is removed like any other crank arm.
Buy the kit with the PC7 head unit. Not the PC8 (much more expensive). The 7 has all of the same data, it's just older.
Carleton, thanks for the advice. By the way you underlined
"invest" I figure you expect the SRM unit to outlast / have better resale value than the other options?
Also, and maybe you already knew this - I got a reply back from Stages tech support to say that their track and road powermeter models have different firmware and so
only the track-specific Dura Ace model was recommended for track use. Apparently the road models can't handle the reversed load from back-pedalling in track environments. So my idea to use an FSA Stages crankarm on the Vision crankset wouldn't work in any case.
SRM it is.
Thanks again