My bike came stock with a 46-15 and it was a bit hard for me to get started, i got a dura ace 17 and noticed an instant ease in my stroke. i kinda muscle up hills so i cant accurately recall the change, skidding went from impossible to easy even though i still suck.

46x16=67.4 gear inches
46x18=71.4 gear inches

Someone will correct me if i'm wrong but the consensus is right around 70 is nominal?

as far as skid patches:

http://sheldonbrown.com/fixed.html#skid

Again someone right me if I'm wrong, this is my first try at being a contributing member.