DanielCoffey

I would appreciate some advice on what front and rear sprocket sizes I should be looking at for a Shimano Alfine on a bike with 700x38c tyres in a moderately hilly town.

I will be using the bike in town as a Utility bike and am aware that 5th gear is the 1:1 gear that I should be aiming to use as often as the gradients permit. I will not be travelling great distances on it. Most of my route is on slight inclines with one long climb and one short but steep ******* of a hill with traffic lights at both top and bottom. I was previously riding fixed on 40/16 which I am now finding a little low as my fitness has increased over the past year.

Thanks for any relevant advice.

Daniel.

tatfiend 

I would not worry about necessarily using fifth gear as much as possible as the difference in efficiency is only a few percent. Gears are to make riding easier so use them.

I geared my Alfine 48-21 IIRC which gives a low of 32.5 gear inches and a high of about 100". For comparison your FG is about 67 gear inches. You could gear your Alfine hub the same as your old gearing though the high would then be fairly high, about 109 gear inches. Your low would be about 35 gear inches. Gear choices are so rider dependent it is hard to say but rear sprockets are relatively cheap and easy to change on the Shimano hub so not too hard to experiment to find what suits you.

vredstein

Like you, I switched from a fixed gear to a Shimano internal gear hub. My fixed was set up with 44/17. I swapped over the entire crankset and used the supplied 21t Shimano cog. The old 44/17 fixed fell must about in the middle of the 44/21 gearing of the internal gear hub.
Keep in mind that if you were to use a 16t cog with the Alfine, you would only be able to install it dished outward. Only cogs larger than 19t can be set up dished inward without removing the drive side dust cap.
Smaller rings and smaller cogs wear out faster than larger rings and larger cogs. Rear cogs are smaller, so they wear out faster than chainrings. So you should try to use the largest rear cog to achieve the appropriate gearing. If you're thinking about trying a higher gearing, Usually the hub is supplied with both a 19t and a 21T cog. Your best bet would be to try to set it up with the 21t cog first and see how it works. If it's too low, you can use the 19t cog, and just shortening the chain. If you try the 19t first, cutting the chain to the appropriate length, then find out it's too high, the chain would be too short to use with the 21t cog.

mconlonx

I was running 46/19, but rarely got into the top few gears. So just recently I went down to 44/19 (at the time, I was under the mistaken impression that I was running a 48 chainring...), and things seem better. I use this setup for a 38 mi r/t commute on a route with some smaller hills. If there were bigger hills, I'd probably drop the gearing even more, maybe try 44/21

DanielCoffey

Thanks folks - looks like 44/21 is my starting point. I am hoping to get the wheel built in a week or two and I will make sure to ask them to let me keep the 19T from the Alfine kit too.

Cheers.