When I got my Felt Z3, one of the problems I had was installing my SRMs. The SRMs need a magnet to determine the rotation of the cranks for calculating power (and for getting cadence data). Usually, this is mounted on the cable guide screw below the bottom bracket. However, since the Z3 has internal cables (Di2), there’s no screw to use for mounting. SRM recommends putting the magnet in place using double-sided tape, which is what I’d done, but it didn’t fill me with confidence that it wouldn’t drop off at some point, especially given the wet Scottish weather. I wasn’t too keen on using some of the other solutions such as hot glue or epoxy on the new frame either.
Recently, I came across this post on Facebook from K-Edge, showing their chain catcher with an integrated magnet for SRM and Quarq power meters – exactly the solution I was looking for!
Tracking one down provided quite difficult, and I eventually ordered one from Excel Sports in Bolder, US, as there didn’t seem to be any dealers in the UK or Europe.
Fitting proved pretty straight-forward; simply replacing the front derailleur bolt with a longer one that holds an adaptor in place, then securing the chain catcher with a smaller bolt (hint – make sure you mark the vertical position of the front mech before removing the bolt!).
My only minor complaint about the device is that the screws which hold the magnet in place project slighted beyond the rear face of the chain catcher and, in some gears, rub slightly on the chain. I’ve got the catcher set at the maximum available extent, so, short of filing the slot in the device slightly longer, or fitting some small washers, there’s not much I can do about this. As I said, though, it’s only a minor complaint.
I’m sure this is a wider problem with carbon frames, and I hope SRM come up with a better design for mounting their magnets, or, even better, use internal accelerometers and do away with the need for the magnet all together. I’ve noticed that the latest Quarq firmware update now allows the device to transmit cadence data using the internal accelerometers. I’m not sure if this is designed to be used instead of requiring a magnet or simply as a backup if the magnet is lost during a ride.