Does anyone know the effect of headwind / temperature on cycling speed?
Specifically a 10-12 mph headwind and temps 52 degrees. Flat terrain. I am just l;ooking to rationolize what I feel was a subpar training ride (at least avg mph wise) yesterday.
I am sure that a PM would have helped me based on watts but I train sans power nor do I use HR monitor. I like to go off PE, or else I would be OCD crunching numbers.
I have seen each 5mph of wind = a 1% grade, I was just curious if there was direct correlation to speed. i.e. 20mph avg pace with no wind would be 18 mph with 5 mph wind etc…
Any insight appreciated. Sarcastic comments also encouraged
fudge the power, putting in whatever number gives you the value that matches the speed you expect. Then use that same power in the second column with the new conditions.
Its really difficult to say how much the wind will affect you unless we have more data. The bike calculator suggested above is helpful to a certain extent, but it is limited in that you don’t know the exact conditions from the rides that you are comparing, and it doesn’t account for gusts, changes in wind direction, etc…
I think Andrew V’s suggestion is probably a good idea, and could provide some interesting info.
Howeva… I would also recommend that you don’t worry about it too much. The things you can control while riding are effort (power output), cadence, and body position. Whatever speed those 3 variables result in is pretty much out of your control, because of wind and hills. Basically, I’m saying, don’t stress too much about what the speedometer says - there are 2 very powerful factors outside of your control that affect speed. If you just worry about effort, body position, and cadence, then overall average speed will take care of itself.
(you could say that food/hydration are also factors, and they are… I’m just including them in the “effort” variable).
And one more thing… to follow up on your question about how wind speed affects bike speed. Here goes: as you increase speed, more and more of your power is dedicated to overcoming air resistance (but there is also some power spent on rolling resistance, etc…). The forces that your power is spent on overcoming change in relative proportion when climbing/descending, as gravity starts to play a more prominent role, but… We’ll just assume we’re talking about relatively flat riding here. When you get up to higher air speeds, the vast majority of your power is dedicated to overcoming air resistance. When I say “air speed”, I’m referring to (ground speed + wind speed), which is the important speed to be worried about when dealing with air resistance. So, for example, riding at 25mph with no wind is the same air speed as riding at 20mph with a 5mph head wind, which is the same air speed as riding at 30mph with a 5mph tailwind.
Why does all this matter? Well, the power required to overcome air resistance increases as a cube of the air speed. For example, if you’re going 20mph, and you increase your air speed by 10% (to 22mph), all other things being equal (i.e. negating the effects of gradient changes, rolling resistance changes, etc…), it will require a power increase of 33%. (I arrived at 33% from: 1.1x1.1x1.1=1.331, i.e., 33%).
Actually power to overcome air resistance is proportional to Vt^2Vg, where Vg is the ground speed (what your speedo says) and Vt is the true air speed. Vt is equal to Vg+Vwind for headwind, Vg-Vwind for tailwind. So not quite 1.11.1*1.1 in one of the examples above.
The other thing to note is that a “10 mph” wind reported by Mr. Weatherman is not a 10 mph wind for you. Wind speed as you approach the ground reduces. Typically wind speeds are 40-50% of reported winds at bike level.
