Weight is one of the most talked about issues in cycling. It dominates much of cycling technology, feels good when it isn't there and sometimes loses races. Just how important is it?
This simple calculator uses the model derived by Papadoupoulous to estimate the gain in speed after the rider and machine lose weight. The estimate uses the ratio of speed on a slope at a given power output and the speed at the same power output when riding on the flat. If this ratio is called u - that is u = (speed on hill) / (speed on flat) then the increase in speed up that hill for a given weight reduction is expressed as:
%increase in speed = %decrease in system weight * (1-u^3)/(1 + 2u^3)
Rules of thumb, pp 140-142, Bicycling Science 3rd edition, David Gordon Wilson, The MIT Press, 2004, ISBN 0-262-73154-1
So, plug your starting weights and dream weights into the fields and note the effect. Of course, this does not take in to account the extra fitness achieved while shedding those extra kilo's on the rider! In truth, this is likely to be far more important than saving a few [kilo]grams on the bike.