Originally Posted by
aliasfox
...One thing I've noticed over the past few rides is that I'm more likely to catch up/pass other riders as the road pitches upwards, but strangely enough, have the most trouble keeping pace on flats or slight descents.
What's strange about this is that I'm not a small guy...
Seems like what you observe conforms with the laws of physics. Gravity accelerates objects at 9.8 meters per second per second, regardless of the weight of the objects. So gravity isn't going to accelerate a large person any more than a small person. But more weight on the tires means more rolling resistance, which may make you go slower. A heavier person putting out the same power should go slower downhill than a lighter person.
On the uphills you do have the disadvantage of having to pull more weight up the hill, so you should be going slower up hills too (holding power output constant). My point is: the disadvantage a heavier person has going uphill isn't offset by any advantage going downhill, because the acceleration due to gravity is not dependent on weight.