A look at how much time and effort we can save by losing weight from either ourselves or our bike. We all know that saving weight helps us to get up hills, but how much will we save, if we can shave off 1Kg from our bike (or lose 10KG off our tummy) ?
As a rough rule of thumb, I had the idea that for a 100 meters ascent, saving 1Kg would give you an extra 2 seconds.
Analytic cycling have this program to calculate approx time saved from losing weight.
I put in figures for next years Rake hill climb
- 900 metres.
- Height gain 100 metres
- Average Gradient 11%
- Weight of rider 61Kg
- power 500 watts
- Time Saved – 1.7 seconds
This seems about right from my own unscientific tests with different weights on the bike.
By, the way, in 2005 on the Rake, Ben Greenwood beat Jim Henderson by 0.3 seconds. In other words the winning margin was 0.3 seconds or 170 grams.
What About a Climb like Alpe d’Huez?
photo Maurice Koop
- 14 km distance
- average gradient of 8.1% (max gradient 10.6%)
- Height gain 1071 metres
- power 400 watts
- 1Kg saved = 24.16 seconds
Lose 10 Kg and you will be able to climb Alpe d’Huez 4 minutes quicker. No wonder, heavier built riders like Mark Cavendish can never compete in the mountains.
Empirical Tests on Alpe D’Huez
According to this site (Alpe d’Huez weight). A rider tired climbing Alpe d’Huez at constant power of 275 watts. With 1.8 extra Kg. It took an extra 66 seconds – which is very close to what the model suggests for 1.8Kg (64 seconds) .
Losing Weight on the Wheel
It is argued that saving weight on your wheel gives an even bigger advantage. This is because a wheel rotates at twice the speed of your bike. Therefore, extra power is needed in accelerating wheel weight. According to the empirical tests on Alpe d’Huez adding an extra 1.8Kg to wheels was an extra 1 minute slower than putting the weight on the bike. Therefore, if you can some lighter wheels, the benefit from the weight saved will be greater.
Test Results from Alpe d’Huez
- 52.01, 275w – Normal bike + 1.8Kg extra water in tyres(!)
- 51.34, 277w – Normal bike + 1,8Kg extra water on bike.
- 49.40, 278w – Normal bike
- 50.38, 273w – Normal bike, reduced tyre pressure only 3 bars.
Other issues in Weight Saving
Power. When climbing it is not all about weight, but also power transfer. If you lose weight at the expense of rigidity and strength, the gains may be lose. When I switched from Aluminium frame to Trek Madone 6.9 Carbon fibre, I felt a stiffer more powerful bike – the weight was actually the same.
Aerodynamics. At certain speeds benefits from reducing aero drag outweigh weight savings. Thus a slightly heavier time trial bike may be faster than a road bike on a hill climb of 3%. (as some found out at National Hill Climb Championships)