Hello, and sorry for another gear ratio question I am currently peddling a 32/16 ratio on a 29er but I need more speed as I find myself peddling like a madmen to reach 15 KM/h. I live in a relatively flat area with one 20 degree hill that is about 700 metres and I will have to go up/down for many years are I do plan on commuting to my school. My ride is about 7 KM each way. Would a 38t chain ring be suitable or even a 42? My LBS doesn't have 38 but it was recommended. Any tips?