interesting question as to why this air shock works while the mechanical spring seems to give a less efficient ride? I think this is because the this air shock is simple, you set the air pressure to match your weight and what size "bump" you want the shock to absorb. The rest of the time the air shock gives the Quest the features of a "hard tail" mountain bike. Which means the Quest will accelerate much faster, climb better and the rider will experience less fatigue. For my 150lbs and a bump size that equals the drop off my drive way at home, I use 130 psi. This pressure, for my weight, will some times result in activation of the shock going over rumble strips at 25 mph and the rest of the time I'm in " hard tail mode". I could never adjust the mechanical spring enough to give the same results.