
mtbr member
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Comparing two rider's power.
I am curious what is a good rule of thumb (nothing too complicated) to compare two riders. I usually ride with my buddy. He blows me away on the climbs. On a recent 3 mile 700 ft elevation climb, I did it in 23 minutes (best time for me). My buddy did it in 15minutes.
His stats are:
age: 34
ht: 5'2
wt: 115 lbs
Bike: All mountain 6" travel ~ 34lbs.
Me:
age: 34
ht: 5'7"
wt: 158 lbs
Bike: All Mountain 6" Travel ~ 27 lbs
I understand the power to weight concept so thats plays a big role in his time. However is there calculation that attempts to normalize the results by taking into account rider weight, bike weight, time, distance, age, elevation, etc.
Look forward to hearing others response.


From your data you can do a quick comparison using the analytic cycling Forces on Rider (Power given Speed) calculator.
Forces on Rider
Convert mph to m/s calculator
Time, Speed and Distance Calculator
Analytic Cycling entries:
Frontal area 0.5 m2 (default)
Drag coefficient 0.5 (default)
Air density 1.226 kg/m3 (default)
Rolling Resistance entered as 0.08
Cadence 90rpm
Crank length 175mm
Calculate the gradient of the hill (elevation (ft) / distance travelled in feet x 100)
700/(5280*3)*100 = 4.4% gradient
Gradient in the analytic cycling calculator is a decimal so entered as 0.044
Buddy + bike 115lbs + 34lbs: Weight = 149lbs (67.58kg)
Time for climb: 15 min
Average speed 12 mph (5.36m/s)
Average Power Output estimate from calculator 208.3 watts
Power to Weight Ratio: 208.3 watts/ 52.16kg = 3.99w/kg
You + bike 158lbs + 27lbs: Weight = 185lbs (83.92kg)
Time for climb: 23min
Average speed 7.82 mph (3.49m/s)
Average Power Output estimate from calculator 155.9 watts
Power to Weight Ratio: 155.9 watts/ 71.67kg = 2.17w/kg
That's a rough estimate of course. It's probably a slight underestimate of your power outputs. If it's climbing a rough track then rolling resistance will be higher. You also need to add in the weight of riding kit and equipment you were carrying. If you had a full backpack that can add quite a bit of additional weight which would make you have to work harder to go the same speed.
I did a quick check of what the calculator numbers look like using my own figures from a 3 mile 4.5% gradient climb that I rode up earlier this year. Those average power output estimate figures look like they will be fairly close to what you would see riding with a power meter. Give or take 1020 watts perhaps.
Me + bike 149lbs + 24lbs: Weight = 173lbs (78.47kg)
Time for 3 mile 4.5% gradient climb: 17min 54sec
Average speed 10.1 mph (4.50m/s)
Average Power Output estimate from calculator 197.5 watts
Actual power output from my Powertap 212 watts
Power to Weight Ratio: 212 watts/ 67.59kg = 3.13w/kg
.
Last edited by WR304; 10122011 at 03:48 PM.

Very interesting stuff. I would not have thought the wattages would be so disparate. I would have attributed the time difference to weight and assumed wattage was very similar.
Just curious, can anyone do the calculations to determine what wattage the OP would need to generate in order to match his buddy's climb time?
Thanks

mtbr member
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Originally Posted by Stumpjumpy
Very interesting stuff. I would not have thought the wattages would be so disparate. I would have attributed the time difference to weight and assumed wattage was very similar.
Just curious, can anyone do the calculations to determine what wattage the OP would need to generate in order to match his buddy's climb time?
Thanks
3.99 w/kg / 2.17 w/kg = 1.84
1.84 * 155.9watts = 286.9 watts required to have the same w/kg ratio as the other rider (not including bikes, same w/kg metric the post above used).

Do you guys upload rides to GPS Bike Routes and Cycling Training Log  Strava? It will do the power calculations automatically for you and you can compare your times, power output, and even HR against anyone else who as ever ridden that segment and uploaded their ride to Strava. Totally addicted to that site.


mtbr member
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Great stuff WR04! I appreciate your response. The math does justify the results.
The example above is an easy climb. We rode together on a tougher climb 3 mile 1,600 ft gain (average 10% grade) and the separation time was much greater at 28 minutes. I average about 34 mph, per my garmin 305. Based on my math, my buddy conquered this climb at an astonishing 6 mph. Although the average grade is 10%, some parts are close to 2025% for 1/8 mile or so. Simply amazing how some folks can climb.
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