Originally Posted by
Bacciagalupe
When climbing, you're fighting gravity; most (non-pro) riders won't ride fast enough up a hill for drag to be a major factor. Even here, though, weight is a smaller factor than you think;
Chris Carmichael, Lance Armstrong's coach, describes the impact of adding 2.5kg (~5 lbs) as adding 38 seconds off of a 20-minute long, 5km, 1200 foot climb -- huge for a pro, noticeable for an amateur racer, inconsequential for everyone else.
I think that on any club ride with some drafting falling out of the group -- which the five pounds would do with riders of equal strength on a moderate hill -- will have a big effect since once it brings you out of the paceline, you have to work hard to get back in.