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As a non-professional biker who commutes on a bike daily I've been noticing that some factors that I didn't think would make much difference in how fast I go or how quickly I get tired have a much bigger impact.

For example, sideways wind. I did not think that a 5-10 mph wind from the side would slow me down as much as it does. Even tail wind doesn't seem to help.

Another is cold. I think that I can bike much faster when its 30C outside vs 0C. Its a little bit hard to say though because I can never compare them side by side.

This question may seem a bit vague, but what other factors affect performance in either positive or negative ways that one would not necessarily consider as making much of a difference?

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Good question! Regarding the wind, drag is proportionate to the square of the difference between your speed and the wind. Tail winds don't help much because as you bike faster, that distance gets small very quickly. Also why doubling head wind speeds actually quadruples the apparent effects. –  John Doucette Feb 27 '13 at 17:12
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Is there any way to make this question a little more concrete? Perhaps there could be a few separate questions about the issues (for example, What makes me go so much slower at 0C than at 30C?) –  amcnabb Feb 27 '13 at 19:48
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I agree with you on both counts. A "quartering" wind is almost worse than a headwind. I think the geometry (and law of squares) works out that a side wind increases the apparent headwind, in addition to the problem that a side wind demands additional energy to balance the bike and hold it on course. And a number of cyclists have noted that particularly on cool, slightly foggy mornings the bike just seems to be moving through molasses (even though physicists assure us this is not the case). –  Daniel R Hicks Feb 27 '13 at 23:08
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As @amcnabb notes, this question is a bit loosely defined. However, I think it would be a great community wiki. –  jimirings Feb 28 '13 at 6:34
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Are you kidding? Tail wind can provide a stupendous boost in speed. With even a moderately brisk tail wind, I'm keeping up with cars. At least until the next hill. Also, I've tried drafting behind the tail gate of a large truck. Boy, what a difference that makes. Air drag is the culprit in cycling, make no mistake. There are few losses elsewhere. You've got your tires well pumped up for very little rolling resistance and the machine has lubricated bearings. –  Kaz Mar 1 '13 at 3:00

5 Answers 5

Some factors that affect day to day athletic performance are:

  • the degree to which your muscles have recovered from previous strenuous work. It is impossible to push the pace everyday, and hit a consistent performance level. Day to day consistent performance is only possible (far) less than maximal effort.

  • symptom-free infections. It's possible for your body to be fighting some virus, yet fully recover without ever showing symptoms. For instance, you could have a cold virus, but you have no runny nose, no sneezing, no stuffed sinuses. However, when you go running, there is this mysterious extra 1:15 added to every mile which has no obvious explanation like muscles not recovered from prior hard training.

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+1 for recovery. The symptom-free infections sounds a bit unfalsifiable to me. You might very well be right, but if there are no other symptoms than slight athletic underperformance, how can you ever be sure. Couldn't it just as easily be lack of sleep or the wrong kind of food (even an allergy)? –  James Bradbury Mar 1 '13 at 8:43
    
Alas I was going to add food reactions to the list, indeed. –  Kaz Mar 1 '13 at 19:19
    
@JamesBradbury A lot of pros measure their resting heart rate daily, and can see an increase of a few beats/minute 1-2 days before any symptoms of illness become apparent. –  pgs Mar 6 '13 at 22:39

Road quality has an amazing effect. A smooth and freshly paved road vs a worn down road, where the tar has leached away and it is very rough makes a real difference on performance.

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But fresh asphalt pavement can feel like you're riding through sand. The asphalt actually "gives" to enough of a degree that you lose energy there. –  Daniel R Hicks Feb 28 '13 at 16:05
    
@DanielRHicks True enough. Takes time to 'harden'. But that is fairly fresh, vs smooth/new pavement. Worst is probably that annoying concrete with all the grooves for traction. Hate that stuff. –  geoffc Feb 28 '13 at 17:17
    
I've noticed "fresh" asphalt producing that extra drag for months after it was laid -- stuff that was laid in early June was still noticeably "slower" in August. –  Daniel R Hicks Feb 28 '13 at 22:58
    
@DanielRHicks Really? I am not sure I have experienced that before. Neat. –  geoffc Feb 28 '13 at 23:21

I'm a commuter who has to carry things like books, a notebook, food for the day, bike lock, etc. I should say that it makes a striking difference whether you carry stuff on your back or on a bike rack -- a heavy bike is not as bad as a heavy backpack, in other words.

Another thing that I've noticed is that my performance decreases if I ride five days a week for prolonged periodes of time, compared to having an extra day (or two) off a week, or having a week off in a month. Having rest is important, not only constant training.

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is back strain the only reason why a bike rack is better than a backpack? –  mkoryak Mar 1 '13 at 18:55
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@mkoryak It not only affects back strain, but muscle fatique when you are riding out of the saddle. It's also a lot cooler to not have a backpack on your back. Having a backpack on is kind of like riding with a jacket. –  Kibbee Mar 1 '13 at 21:20

Boozing the night before has a dramatic effect.

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I'm not sure that this qualifies as a "subtle factor." –  jimirings Feb 28 '13 at 6:29
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its subtle if you booze the night before very often –  mkoryak Feb 28 '13 at 17:18

Small changes in bike fit make dramatic differences in performance. Heat and humidity make a big difference.

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I was having some comfort issues on the seat of my bike. I thought it was the seat, but after moving my seat about 3/4 of an inch forward, I found all the problems with the seat comfort disappeared. Small adjustments can make a world of difference. Ensuring the your bike first right, and that the seat and handlebars are properly aligned can make a huge difference. –  Kibbee Feb 28 '13 at 15:04
    
But the first one doesn't change from ride to ride, unless you have loose bolts (e.g. your seat post slips down and you don't know it), and the second is obvious (you know you're struggling because it is hot and humid). Not exactly a "subtle factor". –  Kaz Mar 1 '13 at 20:18
    
@Kaz If you're the kind of person who has a quick release seat, and you take the seat with you every time you lock up the bike, it's very probably that the seat position would change over time, which would ultimately change bike fit. Even the difference from riding with thin soled sandals to thicker soled sneakers can change how the bike fits you as it effectively changes the length of your leg. –  Kibbee Mar 1 '13 at 21:17
    
@Kibbee Ah yes, good point. It might be a good idea to stick a piece of tape at the insertion line, or make a mark with a permanent marker. –  Kaz Mar 1 '13 at 22:01

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