What's What With Watts...

A few days ago I published a post on choosing a power meter and, though it seems to have been well received, I have been asked some follow up questions.

Firstly it seems that there is some interest in knowing what kind of power output is attainable and how does your output compare to others. To try and answer this I have broken down some previously published data and averaged out the results into four rider groups. Lastly, so that it is possible to compare riders of differing weights, I have broken down the power output into watts per kilo of body weight

(a kilo =2.2lbs)

Rider	1 Minute Burst( watts per kilo)	Maintained (watts per kilo)
Pro Tour Rider	11.2	6.1
Cat 2 Rider	8.85	4.6
Cat 4 Rider	7.6	3.75
Regular Recreational Rider	5.85	2.4

The higher wattage figure in each category is what the average rider, in that group, can reasonably expect to sustain for 1 minute. The second, lower figure, is the average output for a usual distance ride in each group.

These figures are by no means written in stone and I have done my best to average everything out with the intent of giving you some kind of baseline in each group. There are plenty of riders, in every category, that produce figures well outside of the norm and if you want to compare your wattage to your favorite tour rider then a five minute search online will glean you a set of figures to use. Top sprinters are capable of producing around 1200 watts output over the last run to the line and top climbers are getting close to 525 watts on extended climbing stages. Tour guys love to show off their power figures I have found…

 

The Second questioned, that has been asked more than once. Is there a way to calculate watts without a power meter?

Well, kind of. The first thing to remember is all the variables that act against your forward motion, as mentioned in my original post, the terrain, weather, equipment etc; all act against you gaining an accurate set of data from anything other than a power-meter but, by choosing a flat course and a mild day with no adverse wind conditions, a fair judge of power output can be recorded.

Using the table below, again I have taken an average of many power output readings to try and lessen inaccuracies; you can see what kind of power is required to propel you along at a given speed. The data used in the calculations all came from drop bar road bikes using tires from 18 to 25 wide. There may possibly have been the odd 28 in there too but not enough to make much of a difference.

The following is the chart that was produced.

Speed,(kmh)                                     Watts

20                                                           78

25                                                           123

30                                                           186

35                                                           273

40                                                           378

It is interesting to see how the wattage required to increase your speed grows substantially the faster you go. At low speeds the wind resistance plays very little part in holding you back along with other resistance factors. However the faster you go the more wind plays a part. This is because the resistance increases in line with the square of the forward velocity. All pretty technical but this is the basic factor that we have battled with since we decided to start going places on something else other than our feet. The bottom line is that the better you get the harder it is to get even faster.