I have a dual suspension mongoose aluminum frame that I had bought at a mass retailer. It seemed like a nice enough bike and I have been riding regularly all spring. Problem is I'm 6'1" and always felt cramped. There is a 2.7 mile loop that I have been timing myself on just for kicks. Since purchasing a correct fitting trek 4500 hardtail my time has dropped from a little over 18 and 1/2 minutes to about 14 minutes flat in less than 1 month. I don't get as tired and get to extend myself more. I'm sure some of this has come from learning the trail better but I attribute much of it to the right fit and equipment.