I do a lot of fixed gear riding, racing and therefore training. So I got myself some Vector 3 two weeks ago and started using them whenever possible and I have had them on my fixed gear bike and my road bike. I noticed the following here and I am a bit angry about this. The bikes I mention here weight almost the same and are pretty similar anyway (crank length, size, etc) except with one I can coast and with the other I cannot. I even ride the same gear ratio that I ride on the fixed gear on the road bike most of the time because I am so used to it.
- Calories for the exact same track differ a lot. I have a daily 15km commute (one way) and it almost always takes the same time to ride it. Without a vector the kcal are within 10kcal every day. With the vector I get ~350kcal on my road bike and ~230kcal on my fixed gear bike. Even though I work much harder on the fixed gear bike not only because I have to backpedal to brake or slow down and I cannot coast.
- VO2max and performance index are off: On the road bike I start with a performance index of +10 and end at +12 ALWAYS with every ride so far. And I find it pretty easy to drive this up as well. On my fixed gear I struggle to stay above -2 at all times. It took me 6 rides to get from the initial VO2max of 37 to the green area on my road bike. I cannot manage to do the same on my fixed gear bike. Even though I output much more power over a much longer time in total.
Things I have noticed with VO2max: I find it easy to drive the performance up on my road bike as I have said and then whenever I think it might decrease again I start to coast more to have it stay the same. I cannot do that on a fixed gear. So even though I output 0W when just letting the pedals move under my feet or backpedaling for slowing down (which the vectors don't notice at all) the performance index drops instantly. So VO2max does take pedal movement into account in an IMHO wrong way. IMHO it should decrease when coasting to long and not going downhill.
So the main difference here is coasting vs not coasting and even pedalling when slowing down. The other difference is that even though NP is higher on my fixed gear I pedal differently on both bikes. Why on my road bike my initial power is not that high but I output a higher power while riding to keep the speed. On my fixed gear I output much more power and get off the start much quicker initially but then I pedal much more efficiently over long distances so that I need a bit less power to ride even faster than on the road bike.
An example to make things even more clear why I think the values are fishy: Last friday I took my fixed gear bike for an easy (for me) 50km ride where I have averaged 30kph on bike paths that go around my hometown and did a 40kph average minimal effort sprint which lasted 10 minutes and still VO2max dropped to -2 and stayed there. Afterwards my VO2max told me that my fitness level is that of a 50yo guy. Yeah right. While on the road bike I don't even break a sweat and get a performance index of +12 easily for every ride so far.
Long story short: does anyone notice similarities here? Is there a thing that I can do to get around this imho erroneous behaviour? If not, is there at least a switch to turn off VO2max altogether? I really cannot ignore it since it is present everywhere and it is really distracting to see the values that are plain wrong.