Am running alfine hub on 26er rim. front chainring is 36 teeth, rear cog is 23, i want to gear it by changing out the rear sprocket, changing to a 20 or 18 is that going to gear it up or down? cheers

up

http://www.sheldonbrown.com/harris/shimano-nexus.html

smaller rear sproket = higher gear – same as any other set up

With an 18 the ratios are almost identical to an 11/34 caseette

Thanks have just ordered a 16 ,)

online calculator here also