Weight, w/kg and climbing

Triathlon Forum
1

Is there a back of a fag packet way of calculating what a 1, 2 or 8 percent drop in body weight would do for a given time on a fixed distance climb?

I’ve repeated the same climb 5 times in the last week at different wattages. Conditions for the sake of this experiment were basically similar - same time of day, same weather - there is probably a wind difference but its negligible relative to me being fat

Its 4.77 miles 1050 feet in elevation

30.28, 9.5 mph, 221 NP, 215 AP, Cadence 61, 2.79 w/kg
31.27, 9.1 mph, 219 NP, 210 AP, Cadence 58, 2.72 w/kg
33.01, 8.6 mph, 177 AP
43.12, 6.7 mph, 154 NP, 146 AP, Cadence 57, 1.89 w/kg
48.32, 6.0 mph, 132 NP, 126 AP, Cadence 55, 1.63 w/kg

I figure I am at least 6, and probably closer to 8kg over my ideal weight. I rode a bike which is at least 2.5 kilo’s over my tri-bike and I am ridiculously out of condition for a variety of reasons. (the bike also had 45 gravel tires on it)

Is there a way of estimating the difference weight would make for a given time without resorting to a calculator? a rule of thumb, if you will? e.g. 1% of weight is X% of speed all things being equal?

Thanks

2

Not that I know of but this works well.
http://www.bikecalculator.com

3

Dr. Ferrari Method works well for climbs at low speed: VAM (vertical m/hr)/(2+gradient/10)= w/kg*100 of rider assuming ~8kg of bike/kit.

For example if your VAM on the climb in question is 1000 and the gradient is 7% the equation would be 1000/2.7= 3.7 w/kg. From here you can play with the variables and figure out how much faster you would climb with less weight and more power. Basically take your new w/kg and multiply by 2+gradient to get your new VAM…

For you example: You climb 320m (1050ft) in a best time of 30.5 minutes for a VAM of 629. Average gradient is 3.9% if my metric conversion is right. This estimates your w/kg to be 2.63. Improve that by 8% to 2.84 and you can expect your VAM to increase to 680. This would have you finishing the climb in ~28:15. You definitely have to be mindful of wind on a climb of only 3.9%.

Its not perfect, but once you get used to the formula you can figure this stuff out pretty quick. Kind of fun if you are a Strava geek.

4

Your formula works reasonably well on hills. the steeper the hill the better the accuracy. Shave 1% off your weight and you’ll climb 1% faster.