I'll go ahead and open Pandora's box. I just got this pretty awesome 2001 Bianchi Pista but the gear ratio is a tough 48x15. I've been out of the fixed gear game for a few years and don't have hulk legs, so I was thinking either 48x17 or 48x19 would be easy to get back into, decent for city riding, and would give me a good number of skid patches. The city is fairly flat but there are some gentle and steep slopes here and there. It is Oregon after all. I have limited funds and don't want to swap out chainrings, hence the cog. According to Sheldon Brown's Gear Calculator (with 165mm cranks, 23c tires), 48x15 is 84.1 gear inches. 48x17=74.2 GI. 48x19=66.4 GI. I used to ride 42x17 (64.9 GI) in a very hilly city and liked it, but I wonder if 48x19 will cause me to spin out on flat ground, hence the 17t cog. I can spin but also don't want my legs to be egg beaters at 20mph. Any advice is appreciated.