Power meter upgrade on 2015 Surly Long Haul Trucker I have a 2015 Surly Long Haul Trucker with a Andel RSC6 crank and Shimano UN-55 bottom bracket. Is there a crankset I could replace that with that would be compatible with a single side power meter?
Power meters for square taper BBs are hard to come by, and usually custom made and expensive.
However, fortunately the Surly LHT has an ordinary English threaded bottom bracket. Just swap out the UN-55 for any Hollowtech 2 compatible external BB, such as the Shimano Tiagra BB-RS500 or 105 SM-BBR60. Then, get any hollowtech 2 crank, replace the left side with a power meter, and you're good to go.
In fact, more recent models of the LHT use hollowtech-2-type crankset systems out of the factory.
I know Stages only sells power meters for 105 and above for road, so it might make sense to get a 105 BB and a 105 crankset, coupled with a 105 power meter such as the stages Gen 3 Power L, or 4iiii equivelant.
If you want more gearing range than a 105 crankset provides, you can mix and match with other cranksets that use the Hollowtech 2 interface, of which there are plenty.