Chainring Size??

[cowboyd]

Hi, I'm updating my L.W.B. to an 8-speed Nexus hub on the rear wheel. Any ideas as to what size chainring to use on the front. Will be switching out the 3-ring MTB crank, and going to a single ring. Thanks, Cowboyd

[TheKid]

It all depends on how low you want the low gear and/or how high you want the high gear. That's also going to depend on which cog you're using, the 19 tooth or the 21 tooth. Sheldon Brown has an excellent internal gear calculator. You can figure gain ratios, gear inches and speed at various RPM of the chain ring. It also covers all rear wheel sizes, and it includes almost all internal gear hubs:

http://www.sheldonbrown.com/gears/internal.html