Q. My brother recently rode a course with about 4,000 feet of climbing. I rode a similarly hilly course. He averaged close to 200 Watts, I averaged 135 Watts, and we rode at about the same average speed.
I have lost weight so I'm down to about 160 pounds, he is about 180. He is upset that he's using so much more power to ride the same speed. He thinks I'm more efficient, but I'm impressed with his power.
Why the big difference? Different course? The weight difference? Efficiency difference?
Thanks for help understanding this new power thing. - LG
A. Hey L.G. ~ Great questions. First, let me say that watts are not watts. What I mean by that is the critical measure for power comparisons from person to person begins with watts produced per kilogram (or pound) of body weight. Raw wattage numbers don't tell the entire power story—of course neither does body weight alone. (Some pretty big guys can ride fast.)
Your current watts per pound are 0.84 and your brother's are 1.1. Theoretically, he should go faster than you do if all other things are the same. The course specifics might be one difference—a bunch of short hills compared to longer climbs. Different riders favor different courses.
Another big issue is likely body position. Using an extreme example, if your brother was using his 1.1 watts per pound to race you, but he was sitting upright with a giant flappy jacket on, his wind-catching position (wind pushing against his chest and the jacket) would be causing a good percentage of his wattage to be spent on overcoming the wind resistance.
If his bike weighs 10 pounds more than yours, that wattage is going into pushing a heavier bike. If he uses heavy tires and doesn't inflate them properly, that's more drag and friction that he's spending watts to overcome.
If you have your tires properly inflated, an aerodynamic position, an aero bike (aerobars and wheels are the biggies) and an aero helmet, then a bigger percentage of your wattage can be spent on powering the bike (speed) rather than overcoming friction and drag. So yes, you're likely more efficient, to the tune of at least 30 percent (110/85 = 30). That difference is huge.
If your brother wants to get faster, he needs to start looking at some of these items. Of course, the "free speed" items are body position and clothing. If he needs to drop some weight, then that's another way to gain speed—if he doesn't lose weight so quickly that he loses strength (and power).
Of course, you may not want want to tell him all of this.
Put your power to the test at a cycling event.