Ah, okay. At first I was like, "woah, massive chainring! That's pretty badass." But then you said it was a 48. (Most standard 'big rings' are 52s or 53s, usually not anything higher.)

What type of gear cluster do you have in the back? 6 speed? 7 speed? 8, 9, 10 speed? What is it? With some older styles (freewheels) you're limited to a minimum 13t small cog, while newer designs (cassettes) allow you to go down to an 11t even.