Below is some data from a race I had 2 weeks ago. I had some brake caliper/pad issues less then 12 hours from my race start and had to scramble to get a new rear brake pad setup. A local shop in Lake Havasu sold me the incorrect brake pads that were just a slight bit too thick for my break setup (didn’t notice till after the race when I got home and had to sand down the brake material to get the pads to not rub). In the end I didn’t have time to correct it and raced anyways knowing I had a bit of drag.
I was leading the race with good legs for the 1st 2 laps with a 3 minute gap on the 2nd place guy and flatted. However, my legs felt DRAINED at the end of the race even after flatting for a 2nd time and finishing out in 9th place. Low and behold, my meter on the bike told the whole story, I was losing nearly 60 watts per pedal the whole race from my dragging brake. Left side shows the 1st main climb and then the whole race course with math calculated power numbers based on rider weight, bike and a few other variables. Right side shows the same segments but what my power meter was reading. I averaged 332 (4.45 watts/kg) watts for the 1st 20 minutes of the race, however by math I only averaged 250 watts (3.34 watts/kg). In the end, my brake cost me nearly 1,000 extra calories (same as riding for an extra 1.1hrs) and 15-20 minutes of total time for the race.