Thinking of Dan here, the KMC 42x20 setup is roughly the same as 36x17.
Thanks, Martin; a good thought indeed!
I am currently running 1/8in sprocket and chainring on my Fixie which I use rather more than expected. It is a converted 1970 road racer with long-ramp Campagnolo 1010 dropouts that allow plenty of room for tensioning the chain. The bike is setup for a perfect 42mm chainline with no deflection.
I started with 3/32in gears and a compatible derailleur chain, then swapped in the 1/8in chain and found immediately better life, but it is hard to know if that is due to the larger bearing surface area or due to construction or metallurgy. I played around a bit on spacing out the chainring to see how tolerant the wider 1/8in chain would be and found to no surprise it will tolerate some misalignment when paired with the narrower chainring and sprocket. The third iteration I'm running now is a full 1/8in drivetrain and if is showing the least wear as expected. Fixies are pretty hard on chains because they see tension under braking as well as under drive. I'm using the bike a lot on rides in hilly terrain and even on singletrack for up to 200km day rides and find it surprisingly good and amazingly versatile for such a simple setup.
I've been thinking about someday switching to a 1/8in setup on my Nomad and may do so at some point but I think the current setup will last "long enough" with reversing to still be a good value, so I'm in no hurry to convert. I did switch to the Rohloff slim splined carrier and have been pleased with the result so far. It sure will make reversing the cog while on tour an easy task but I heartily agree with George about the value of periodically removing the carrier to relube the threaded interface with anti-seize.
Still hoping Hebie will someday come out with a Chainglider to fit my present 36x17 setup so I can convert at minimal cost without having to invest in a new chainring and sprocket.
Best,
Dan.