Somewhere in the range of 75 gear inches or slightly less seems to work best for me for hills. Let's me get up them and not spin too crazy fast on the downhills. I use a 44x16 (74.2 GI) on my Kilo and a 45x16 (75.9) on my other fixed gear. If you don't want to change chainrings (and mess with chain length) hooters recommendation of 48x18 will get you 72 GI.