Today I did an experiment to measure just how much additional friction is in a Derailleur as opposed to a single speed setup. An easy test shows that the derailleur has more friction. Take the pedals and spin them backwards in each setup. What you will find is that when connected to a derailleur the pedals stop quickly. In my case in about 1/2 a turn. Whereas in the single speed setup the pedals move easily, in my case more one turn.
I wanted a more quantitative measure of the difference than just the above observation. So I attached a weight to the pedals and measured the amount of weight needed to take the pedals from horizontal to vertical in 1/2 a second. What I found was that the derailleur took 4 times as much weight. This means that the power output needed to just turn the pedals is 4 times more for the derailleur than in the single speed setup.
Next I tried to determine the actual power needed. This was a very crude estimate but I came up with 16 Watts for the derailleur verses 4 Watts for the single speed. The difference of 12 Watts is power that is not going to moving the bike but is needed to just overcome drive train friction.
At the Iola race an additional 12 Watts of power for me would have translated to reducing my race time by two and a half minutes. That would have moved me from fifth to third in my age group.
All these measurements were crude but show that friction is the real enemy and a simple configuration such as a single speed can help lower it by a significant amount.
I want to improve my measurements to get a better estimate of the difference in power so stay tuned.
Mike
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