Originally Posted by Aurelius
I'm told that for hundreds of dollars, I can lighten my 29er from it's current weight of 26 lbs down to 22 lbs. Alternatively, I can rid myself of 4 lbs just by dieting, and it would cost me nothing. So my question is, does taking weight off the bike make more of a difference during the ride than taking an equal amount of weight off the rider?
The best money you can spend to reduce noticeable weight on the bike will be in wheels, tires and secondarily on cranks, cassettes, chains. Essentially, anything that rotates will make a discernible difference. Beyond that, it's all subjective and static weight. It helps tremendously to shed weight from your body and that just takes discipline, the right nutrition and training.
Edit: or you could just man up and switch to a single speed to get rid of all those unnecessary gears, derailleurs, shifters and cables. Then swap out for a light set of wheels with that money you just made to most likely get in the sub-20lb range...