July 29, 2021, 2:51 a.m. -  fartymarty

Andrew, One thing you haven't mentioned is rider weigh.  I think bike weigh must be proportional to rider weight.  A 30lb bike for someone at 60kg (sorry to mix units) is proportional to a 45lb bike for someone at 90kg.  This assumes both riders have a similar muscle %.   Thinking about this more scientificly it makes sense (or at least in my mind).  Heavier riders generate more kinetic energy (KE = 1/2 m v^2).  Therefore heavier riders are putting proportionally more force into components than lighter riders for the same speed.  Components are proportionally stronger as weight increased*.  Therefore heavier riders need stronger and therefore heavier components than lighter riders.  Therefore bike weigh is proportional to rider weight.... \* this is not strictly true as you can increase diameters which increase strength / stiffness without the proportional increase in weight - look at larger diameter thin walled tubes cf smaller thicker walled tubes. What annoys me is comparing bike weights (a stand alone number) and not factoring in rider weight.  Add in rider speed and the equation gets worse.