Ever wondered how much difference it would make if you made your bike lighter? I guess most serious riders once in while have concerns about their bikes whether they are light enough. As previously described the bike weight has impact on performance – especially during climbing. Thus, I thought it was interesting to find out how much difference it makes if you ride a heavier bike up alpe d’Huez. This little trial was performed by the best rider I coach as a part of his preparation for Tour de l’avenir (U23 Tour de France) in September.
In this experiment he had to ride up Alpe d’Huez four times with different setups. He was supposed to keep a pace around 275w on all four rides. The test bike was a Pinarello Prince equipped with Shimano Dura Ace and SRM crank:
1. Normal bike + 1.8L extra water in tyres(!)
This setup was quite interesting and got quite a lot of attention the day before when he had a puncture..! It was possible to fill 900ml into each tyre. Reducing weights on wheels is more important than reducing weight on non-rolling equipment e.g. bike saddle.
2. Normal bike + 1,8L extra water on bike.
This setup also got some serious attention because he rode a relative fast pace compared to most riders visiting Alpe d’Huez. Thus, when he performed the trial, well-trained riders were trying to keep up with his pace because this setup looked so extreme.
3. Normal bike
This setup was a completely normal bike.
4. Normal bike, reduced tyre pressure only 3 bars.
The last setup was ridden with reduced tyre pressure to 3bars. This was a tough finish on the last ride up Alpe d’Huez this day.
Results:
1. 52.01, 275w
2. 51.34, 277w
3. 49.40, 278w
4. 50.38, 273w
1,8L extra weight costs 1.54min up Alpe d’Huez. This is a remarkable test that shows us how important weight savings are when you are riding on steep hills. Also it shows that weight savings on wheels might be more important than weight saving on non-rolling equipment. These trials were only possible because of his SRM Crank that made it possible to compare each ride up the hill. You can make similar trials to test your bike setup if you want to optimize your bike equipment. These tests can be extremely helpful for e.g. time trialists if you don’t have wind tunnel in the neighbourhood.
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How did he get the tires filled with water? I tried that with a football once, and it wasn’t easy to do. He didn’t descend with water in his tires, did he?
I told him to not do that because it sounded a bit risky. He didn’t bring a pump to the top, so he did the downhill with tyres full of water…
interesting but i’m not sure that you can make the conclusion that wheel mass is worse than frame mass.
Although the SRM allowed the rider to keep the power levels similar there are slight differences. In order to draw conclusions some normalisation has to be done.
Taking the normal run (#3) as the bench mark and assuming the 278w is the average for the climb, the total energy used for the climb is 828440J.
Using the same method, the total energy used for each climb is as follows:
1. 858275j
2. 857038j
3. 828440j
4. 829374j
The difference between the heavy wheel and heavy frame (#1 & #2) runs is about 0.15% in total energy required. This is in the range of the typical measurement error. This implies that if the rider put out the same power for each set up the time would be the same.
The difference between the normal climb and the flat tire climb (#3 & #4) is also around 0.11%
From the above numbers I would conclude that it doesn’t matter where the weight is located (rotating vs non-rotating).
Of course to get really solid results the climbs would have to repeated several times (not popular with the rider!)
beebee>>
Thanks for commenting. You’re right, we will need (a lot) more riders to make these results statistical significant. Also there is a couple of other concerns like the weather and the rider’s body weight troughout the day. It is certainly non-scientific, but still, I like the setup and think other riders should try similar things with their power meter mounted.
These results shall be seen as an example of how you can make your own field studies using a power meter. Conclusions shall be made with the above comments in mind.
Jesper
Ps. The rider who performed this workout finished 26th overall in Tour de l’Avenir yesterday.
Our local ‘Alp’ (Jebel Hafeet, Al Ain, UAE) is pretty similar to Alpe d’Huez in length and gradient, I’ve ridden both dozens of times. I recently lost 10 kgs and my times up it improved……exactly 10 minutes. My impression is that your 1 min/kg of weight is pretty accurate on similar climbs. I suspect the biggest improvements come not on a single climb, but, with reduced cumulative fatigue, at the end of multiple climbs, i.e. a long day in the mountains.
I’m thinking the tyres[sic] (sorry, american speller here) may have had some free surface effect issues, hence pushing the time down. I’m almost positive that you could not have removed all the free surface, so the sloshing would have cost you time.
John,
You’re right, there are several problems with water in tyres. I’m planning to do another series of tests this summer so there we will try some different wheelsets instead.
Have a nice day
Jesper
Interesting test but it is inconclusive whether it was the addition of weight in the tires that slowed him down. For example, just looking from the way you setup the tests, you made him do the run with the watered tired first. Could you prove that for the first 3 tests, it wasn’t the rider’s adaptation to the climb that made him do better and better? And the power consumed was highest when he had his normal bike? Thats odd, especially to your point in the beginning of the post.
Powertap doesnt tell you things like mood fluctuations, motivation, and human adaptation to physical stress.
-Ron
Cozy Beehive
Ron,
What kind of adaptations should make the rider faster up Alpe d’huez? The test rider was supposed to deliver a constant power output, not to ride as fast as possible. Contant power output shouldn’t be affected by motivation or physical stress. 1W = 1W ~ happy or not.
Awesome! I’m just about to do the Alpe Duez Triathlon and this is only decent article on weight, scientific enough for me, I’m trying to decide on whether to use my p-tap or not, appr 1200 grams, or Mavic Ksyriums. By the way how much did yout test rider weigh? Thanks for the test.
I live at the base of Alpe d’Huez running a cycling holiday company and keep plugging away at my fastest time – now have a brand new bike on the way which is a few pounds lighter – wonder if it will have any effect !
Heavy tyres mean more rotational inertia to overcome. As a result they affect acceleration much more than they will a steady tempo climb.
One important thing to check if you’re doing exercises like this- did the measured distance traveled change between runs? The distances I get when doing a long climb like this always vary by a bit from attempt to attempt.