i run 48-20, a 65 inch ratio. im a weak ass 5'6 and 65 inches is almost TOO low. Skidding is effortless, any lower and it will be like riding a kids bike. the difference between 70 and 65 is HUGE. any lower than 65 and i would be surprised if you pass 15mph. trust me dont drop below 65 unless you have some kind of knee injury

http://software.bareknucklebrigade.c...it.applet.html

^^that will help you figure out inches and skid patches.

if you want something easily skiddable, id say go with a cog between 18 and 20.