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Discussion Starter · #1 ·
I've asked this question before on other forums and always had mixed responses, i.e. some people say temperature by itself (ignoring wind, effects of bulkier clothing etc) doesn't have any effect on their average speed, while others say it does (suggested causes have ranged from muscles being less efficient at lower temperatures to the effects of the denser air).

I'm in the latter camp. Where I am at the moment it's only just beginning to be consistently above 0 degrees C (32F). At about 5C (40F) I find that my average speed over a given route is 1.5 - 2mph slower than it is in the summer. Some of that may be down to early season lack of fitness (although I've been on the trainer over the winter). However, I noticed the same thing in the autumn/fall; as soon as temperatures got below about 10C (50F) I became noticeably slower.

So I'm wondering if this is a universal experience (maybe some people just don't notice), and if so, if there is consensus on the cause. Or could it be something that depends a lot on individual physiology? Perhaps even age? I'm pretty light and skinny, so not much insulation for the muscles...
 

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corning my own beef
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some of that effect may be due to the way you're dressing; it's possible that the colder-weather gear offers less mobility or introduces aerodynamic drag that effects your speed.

For most people, the same effect applies at the opposite end of the temperature spectrum. My favorite temperature (only in regard top performance) is probably 60F -- no extra clothes necessary, but I'm also unlikely to overheat. In any hard (race-type) effort that is over 75F, I am noticably slower and feel overheated.
 

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Le Misérable
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Sometimes I feel like I have to work harder than I should to go a certain speed when it's at or near freezing, but it's probably from the clothing. Over a short distance it's probably mostly mental.

However, what I'm convinced is VERY real is the toll the cold takes on my endurance: I'm a long-distance kind of guy no matter what the sport, but no matter how well I dress I'm wiped out after 3 hours of cycling at 0C. I can't back this up with science, but I have the sense that my body is spending energy keeping warm, sending blood to frozen fingers and toes, etc. and thus there is less available to keep me pedaling. That might be 100% crap biologically--that's a little out of my knowledge sphere--but the result is too consistent to write off to my imagination.
 

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Captain Obvious
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i'm slower in the cold. i'm probably most comfortable between the mid 60's and upper 70s.
 

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Here in south Texas it never really get that cold but I find my average speeds are faster during the late fall, winter, and early spring when it's cooler. In the summer heat my averages go down.
 

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Cold air is more dense than hot air. It will take more power to push your body through cold air than warm air. It's like adding a couple mph of headwind.
 

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jd3 said:
Cold air is more dense than hot air. It will take more power to push your body through cold air than warm air. It's like adding a couple mph of headwind.


a couple mph of headwind? really???
 

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FatTireFred said:
a couple mph of headwind? really???
Ummm, yeah...me too; I'd like some proof of that claim. Seems to me that a) there are more factors involved in air density than just temperature, and b) the conversion from air density to mph of headwind is probably pretty complicated, if even possible.
 

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BikeRider said:
Here in south Texas it never really get that cold but I find my average speeds are faster during the late fall, winter, and early spring when it's cooler. In the summer heat my averages go down.
I think that speaks to there being a "sweet spot" of temperatures where the body operates most efficiently. Too hot or too cold will hurt the efficiency.

I do notice a diffence between say 40 and 60 degrees and it is not air density.
 

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Yes, air density, as related to temperature and other variables, is a measurable factor. From Analytic Cycling website:

Was it a bad day, or was it Air Density? As an example, Denver, Colorado, at an elevation of 1500 meters with temperature of 24°C and barometric pressure of 29.01 inches of Hg could have an air density of 0.960 kg/m3 (lower than standard pressure). At the same time Wilmington, DE, at sea level with a temperature of 12°C and a barometric pressure of 30.29 inches of Hg could have an air density of 1.253 kg/m3 (higher than standard). Due to differences in Air Density it would require 28% more power to ride the same pursuit time in Wilmington as in Denver, even though 15% is more or less the nominal difference.

Air density depends on temperature, barometric pressure and altitude and to some extent on water vapor (humidity). Air density is calculated here as a function of temperature, barometric pressure, and altitude, neglecting the effect of water vapor which is small.
Also, your tires generate more rolling resistance at cold temperatures.

If you've ever ridden a bike at 40 below you know what I am talking about.
 

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Discussion Starter · #12 ·
Wow, does sound like air density could be significant and could explain a lot. Combine that with slightly increased resistance from bulkier clothing, possibly less flexibility due to the cold, tyre rolling resistance, and maybe that would account for 1-2mph. But if so then it's strange that when ever I ask this question, many people say (or imply) that they aren't slower in the cold. I wonder if they have checked properly, though; I'm talking about when you are trying to maintain a fast speed on your own over, say, 30-40 miles.

Yeah, my favourite temperature is also about 15-20C. If I'm not sweating at all I'm slower, but if I'm sweating buckets I guess I'm slower too, although it rarely gets much above 25C here so I've less experience of that.
 

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JustTooBig said:
some of that effect may be due to the way you're dressing; it's possible that the colder-weather gear offers less mobility or introduces aerodynamic drag that effects your speed.
Nailed it. In the winter here in Wisconsin I don't pay attention to my average speed when I have 3 layers, booties, mittens and feel like Charlie Brown. I know I warm-up faster layered and settle into tempo easier at a slower rate layered like that.

I can't imagine racing with all that on.
 

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Some numbers

FatTireFred said:
a couple mph of headwind? really???
Aero drag is proportional to air density. Air at 40F (5C) is about 8% denser than at 80F (29C), and at 20 mph (32 km/hr) about 80% of your power goes to overcome aero drag. Running these very simple numbers says that temperature alone (air density) costs about 1.2 mph (1.9 km/hr).
 

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anthony.delorenzo said:
Yes, air density, as related to temperature and other variables, is a measurable factor. From Analytic Cycling website:



Also, your tires generate more rolling resistance at cold temperatures.

If you've ever ridden a bike at 40 below you know what I am talking about.
Okay, that looks dramatic, do you gain something at due to less air resistance in "thinner air", but there is also a physiological trade off. Is there anyone in any sport that can claim to have the same endurance in a thin air environment? Clearly there are more than one factor at play.

The same internal combustion engine will develop more power at sea level and at cool temps than at high altitude and warm temps. The human machine performs similarly.
 

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Kerry Irons said:
Aero drag is proportional to air density. Air at 40F (5C) is about 8% denser than at 80F (29C), and at 20 mph (32 km/hr) about 80% of your power goes to overcome aero drag. Running these very simple numbers says that temperature alone (air density) costs about 1.2 mph (1.9 km/hr).
Thanks Kerry. I feel better now. I thought I was slow(er) in the cool spring from sitting on the couch and eating junk all winter. :D
 

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Thanks Kelly and Anthony for putting some numbers to what I posted. I've spent way to many years in airplanes, gliders, hot air balloons and sailboats to not know something about wind and air density.
 

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What Would Google Do.
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Its funny how most? people come on the forum looking for 'answers'...you dont get answers here (or any forum for that matter) only opinion, yes there are answers and some RIGHT ones, but they usually get lost in all the nonsensicle stuff along the way, like in this one where people are talkin about air density on cold days....a little knowledge is a dangerous thing remember that!!. And given that you asked the question before and got a mixed OPINION (as always) chances are it'll be the same this time round! - so not sure what your after? as I said you'll just get another load of opinions and some arguing to the death that their one is the RIGHT one :rolleyes:
 

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Höchstgeschwindigkeit
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Damn, or is it cool? I thought it was the Amino Acids I started taking that has improved my speed and endurance. Was doing some nice pulls this morning at 28-31 mph. Alas, it is probably only air density, or plasibo or the wheaties.
 

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Discussion Starter · #20 ·
Its funny how most? people come on the forum looking for 'answers'...you dont get answers here (or any forum for that matter) only opinion, yes there are answers and some RIGHT ones, but they usually get lost in all the nonsensicle stuff along the way, like in this one where people are talkin about air density on cold days....a little knowledge is a dangerous thing remember that!!. And given that you asked the question before and got a mixed OPINION (as always) chances are it'll be the same this time round! - so not sure what your after? as I said you'll just get another load of opinions and some arguing to the death that their one is the RIGHT one
Well, you quite often get answers, or at least partial answers that you can follow up on. If you assume that even just a small percentage of respondents might know something you don't then the only problem is separating the "nonsensical" from the sensical, and with a modicum of critical evaluation, prior knowledge and common sense that's usually not too difficult. Opinions are often informed, and a little knowledge is the only starting point for more knowledge!

Incidentally I don't think the possible effect of air density on cold days is nonsensical, but that's because some people produced some figures, not just opinions! :)
 
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