If you're planning on skidding with this bike, look at how many skid spots you'll have with a new cog/chainring setup. The calculation is pretty simple. Make a fraction with the teeth on the chainring on top and the teeth on the cog on the bottom (55/16 in your case) and reduce the fraction as far as possible. The bottom number of the new fraction is how many spots on your tire will get worn from skidding (the more the better). 55/16 is irreducible so you would have 16 skid spots. If you were to get a 48 tooth chainring, 48/16=3/1 so you would only wear out one spot on your tire. The most foolproof way to go is to get a 17 or 19 tooth cog in the back since they're prime numbers
edit: blast from the past