Originally Posted by billridesbikes

Going up hill it's power that matters. Weight to power matters too, however not quite as much as people think. A big guy can churn up the uphill at the same speed as you with lower watts/kg, however the number of watts he's putting out will be much higher. Whoever passed you could have just been a bigger guy with much more power.

For example: For a 10% grade with three riders whose weights are 60kg, 75kg, and 100kg all traveling together at 10kpm the 60kg guy will be putting out 230W (3.8 w/kg) the 75kg guy will be putting out 275W (3.7 w/kg) and the 100kg guy will be putting out 340W (3.4 W/kg). So in order to go the same speed as the others the lighter rider has to put out higher w/kg.

Although if you where at a steady 3.5 w/kg and someone passed you at 1.7 w/kg uphill that would be really weird.