Originally Posted by PolishPostal
If most of your riding is on the flats. Considering your chainrings (48-36), I would go with an 11-21 (11-12-13-14-15-16-17-19-21). With that combination you gain the 11 and 16 tooth cogs. Your lowest gear of 36/21 would give you the equivalent of a standard 39/23. With that smallish big ring (48) you will need the 11 cog. The 48/11 is the approx equivalent of a standard 53/12.
+1, with a 48 chainring, I think you will run out gearing around 30 to 35 mph, I rode a bike with 50x12 on sat and ran out at 38 mph.