Originally Posted by
muccapazza
13x28 6 speed freewheels are available
http://sheldonbrown.com/harris/freewheels.html#6 here, for one, a 53 ring with a 13 low freewheel cog would help your speed. I'ld look into seeing if a 7 speed freewheel, the 11x28, would fit, they are just a smidge wider than a 6 speed.
Does anyone really make a freewheel that takes an 11-tooth cog? If so then that would be a good solution since dropping the 14 to an 11 would increase the gearing by over 21% whereas going from a 48 to a 53 chainring only increases it by about 10%.
My Bike Friday came with a 60-tooth chainring and an 11/28 cassette to give reasonable gearing - and it has 20" wheels vs. the OPs 16". So I agree that he certainly does need higher gearing. If a freewheel is available with an 11-tooth cog then that would be easiest. Otherwise he'll need to change the hub (i.e. rebuild the wheel) using either an internal gear or one that takes cassettes with smaller cogs.
Just changing the front ring from 48 to 53 teeth (i.e. 10% larger) doesn't seem like enough of a change to make it worthwhile.