I am riding a Mongoose Switchback 21-speed hybrid. I only use 4 gears, because if I use any of the others, I feel that I am pedaling my keester off and going nowhere. Should I change the crank gears of the rear cassette? Also, if I change the front crank, I surmise that they should be bigger and if I need to change the rear cassette, should they be smaller?
Any info is greatly appreciated.