Is it possible to measure avg power on a ride if you don’t have a power meter on your bike?
Is it possible to measure avg power on a ride if you don’t have a power meter on your bike?
No.
Yes, you can use a computrainer 
Sorry…thinking outside the box
jaretj
.
VERY roughly
http://bikecalculator.com/wattsUS.html
.
If you know the elevation profile for the ride and the wind was not too great, you can get pretty close. You’ll need your weight, and make assumptions about aero drag and rolling resistance… then plug the numbers into a calculator.
Climbs are better because aero drag is less of a factor.
Ok, i have a garmin forerunner 305 that has my whole profile. Is there some program that i can import may data to to get me an avg power reading?
Power Meters are pretty expensive so trying to back into my power somehow
I have a pretty decent idea of my ftp because I have an accurate idea of my weight, my bike’s weight, and access to several 20+ min climbs. I figure this gives me results within 5% or so.
First of all, my guess is that any estimation of power after the fact is bound to be a poor guess.
But most importantly, what good would it do even assuming it was close to accurate?
What use is it to know your power without a power meter?
Is it possible to measure avg power on a ride if you don’t have a power meter on your bike?
Yes. Ride somebody else’s bike that has a power meter. Or, in a tri, look for some rich fat guy’s bike that you beat on the swim. Ride his bike for the race. Put it back in his spot after you are done. He’ll never know it was gone if you are fast enough.
Ok, i have a garmin forerunner 305 that has my whole profile. Is there some program that i can import may data to to get me an avg power reading?
Power Meters are pretty expensive so trying to back into my power somehow
There is a plugin to SportTracks that calculates power from speed and grade. Haven’t tried it (have PM) but I’d start there.
Beware that the altitude/grade data is pretty much wortless from the FR305 - you’ll need to do GPS->altitude correction.
I’m in the same boat you are as far as equipment. (Have the Garmin, don’t have the Power Meter.) Assuming the calculator link provided above is accurate (and I have no reason to assume it isn’t), it is EXTREMELY twitchy based on the headwind measurement.
I put in a set of 20 mph values with no headwind and get: 172 watts.
with a 2 mph headwind this jumps to 200 watts.
with a -2 mph headwind this plummets to 147 watts.
Your Garmin won’t tell you about the direction and strength of the wind, and dead calm is pretty rare around here.
I suppose if you assume the wind is constant for the whole ride and you do a loop it should be affecting your from all directions, so the 0 wind might be close to the average…
Yeah. I am just curious what my avg power output is without spending any more money. I’ll try the sporttracks software. There are a lot of posters on here that give their power output and i’d like some context.
“There are a lot of posters on here that give their power output and i’d like some context”
Keep this in mind for context: a lot of people lie on the internet.
If this is for context (), then take your bike to a friend’s place who has a a computrainer as Jaretj said . But you’ll need to do a proper roll down test and also have a means of keeping tire temp fairly constant once you have done the roll down.
I’d suggesting riding an FTP test at around 35-40 kph wheel speed and keep the press on force at around 2.00 (you don’t need a high press on force if the wheel speed is high). This will give the least divergence on the power numbers…
Once you do this you’ll be set. Or find a climb with 10% grade that takes an hour (hard to find in most areas)… get your time and enter the data on analyticalcycling.com and you’ll have a fairly close estimate of your FTP for the purpose of dick measurement/context.
Or of you really want context, just look at the race results for you vs your buddies…lots of guys with big FTP numbers and even big watts/kilo numbers who choke in racing…race results don’t really care what your training/lab numbers are, although having good training/lab numbers help assure better race results (in general)!
Dev