I wasn't sure if I should put this here or in Road Cycling but my question is:
Riding the same bike, under the same conditions, how much difference in cruising speed could one expect from a 30-pound weight loss?
I know there is a formula out there somewhere and an online calculator that let you plug in different variables such as incline, wind speed, weight, etc. but I couldn't find it and as I remember I had problems getting it to work correctly back when I first saw it.
Last fall I was cruising (60 minutes or more at steady pace) at about 18mph on flat ground with no wind. 28lb touring/hybrid 700c x 28 Bontrager H2 eco tires. I weighed 230 lbs and have the goal of losing 30 pounds by April 1 (I'm about half way there). I'm not looking for advice on training or on getting a lighter road bike (I already have a project road bike in the workstand). I'm just curious about approximately how the loss of 30 pounds of excess (fat) bodyweight would effect average cruising speed, isolated from other variables.
My plan is better training, better bike, and the loss of 30 pounds of excess weight in preparation for doing a couple of charity centuries and being better on group rides. Just for curiosity's sake, I'm wondering how much of the improvement I'll hopefully see comes from the bike, greater strength and endurance, and how much is because of the loss of excess baggage.
A way to look at it would be if I rode one day with a 30-pound weight vest, took a day of rest, and then rode the same course, on the same bike, under identical weather conditions, but minus the weight vest, how much speed could I expect to gain.