I'm trying to deduce the forces acting on a cyclist going up a hill and I need help. There's 2 questions: Q.1 I've looked at online calculator already in existence: http://www.analyticcycling.com/ForcesPower_Page.html http://www.gribble.org/cycling/power_v_speed.html What puzzles me about these calculators is when I caculate the parallel force I get numbers that are different to these calculator. but are the same as http://thecraftycanvas.com/library/...pers/incline-force-calculator-problem-solver/ e.g. for a 5º slope and a 78 kg rider+equipment: -9.81 * sin(rad5) * 78 = 66.6 N "thecraftycanvas.com" get the same result, yet Gribble and Analytic cycling get 38.2 N Q.2 Following on from this, what I am trying to do is calculate what the force are acting on the rider by doing a calibration run down the hill, the other forces (air resistance (wind, pressure), friction) besides gravity being the difference between the force on the calibration run and a hypothetical run just with the force of gravity. So that when the rider goes up hill in X amount of time we can calculate the how much work against gravity by itself and all the other forces rolled together (deduced from the calibration run). Am I missing something fundamental?