I knwo the answer is that you can’t. I also know that it depends on body weight, aerodynamics, and what speeds you are going.
However, I currently have no reference point. I was wondering if people who use their powertaps have any data they can share.
ie…on a flat road you ride 19mph at 200 watts, 21 mph at 240 watts, and 22 mph at 270 watts…or something like that. I just want to be able to map some performance goals with some of my workouts.
Thanks - Barry
Here you go…the answers to all your questions!
Bicycle Speed And Power Calculator2
…it depends on body weight, aerodynamics, and what speeds you are going.
I just want to be able to map some performance goals with some of my workouts.
…air temp, density, wind speed, wind direction, divetrain friction…should I go on?
mapping performance goals like that is a false target. the best way without a powermeter to estimate would be a windless hillclimb.
g
mapping performance goals like that is a false target. the best way without a powermeter to estimate would be a windless hillclimb.
Funny…my boss and I just had a conversation on guestimates at our engineering firm. Right now I work on multi-million dollar projects that begin with exactly this kind of guess work.
You mean you can’t tell me if on a flat road on a windless day that you can’t nail down a range that increasing from 200-250 watts will put you in? Is that a 1 mph increase or closer to a 30 mph increase?
People with powermeters like to pretend that any method of performance evaluation with LESS accuracy is worthless, rather than simply less precise
=)
Those of us without the cash to spend on powermeters at the moment will just guesstimate the wind and keep on trucking
.
mapping performance goals like that is a false target. the best way without a powermeter to estimate would be a windless hillclimb.
Funny…my boss and I just had a conversation on guestimates at our engineering firm. Right now I work on multi-million dollar projects that begin with exactly this kind of guess work.
You mean you can’t tell me if on a flat road on a windless day that you can’t nail down a range that increasing from 200-250 watts will put you in? Is that a 1 mph increase or closer to a 30 mph increase?
Barry,
Having used a PT religiously for 18 months (download the ride data after every ride and analyze in CyclingPeaks), I’m unable to answer that question – and it’s not because I feel that speed is an invalid or imprecise metric to track. It’s simply because I don’t run that kind of analysis (power vs speed for given terrain). In training, I’m paying attention to the power that I’m able to hold for 2x20 intervals, for an hour, across an entire long ride, and so on. Those metrics will give me an indication of the effort I’ll be able to sustain on race day. The speed will be what it will be based on the physics.
If you’re simply looking for swag numbers, then I think you’re best bet is to use a calculator like the one mentioned above (or the “Speed from Power” calculator at http://www.analyticcycling.com). That way you can play with the variables (wind, weight, CdA, etc.) and document how changing those variables changes your result.
Hope that helps!
cramer
At http://www.analyticcycling.com/ there are calculators to play with all kinds of variables (wieght, rolling resistance, frontal area, wheel depth, etc.) and see the results on speed.
Folks also post interesting data in the forum at Biketechreview
Couple yrs ago i did a LT test on a computrainer…
415 watts at 28 mph, hr 158, 105 rpm
Funny…my boss and I just had a conversation on guestimates at our engineering firm. Right now I work on multi-million dollar projects that begin with exactly this kind of guess work.
Funny…my boss and I just had a conversation on guestimates at our engineering firm. Right now I work on multi-million dollar projects that begin with exactly this kind of guess work.
LOL… Engineers are approximately perfect. 
Here’s the last project Barry worked on. Factoring out resonant and natural frequency the basic design was very simple to do.
I ride at **about **22, 23, 24, 25 MPH at 180, 200, 220 and 250 watts, respectively . (With no wind, slope etc. in aerobars.) My bike and I weigh 153 pounds. Does that help? Probably not…
I’m a small guy 5’4" 144lbs
With training wheels
150 watts gets me about 20 mph
200 watts gets me about 22.7 mph
250 watts gets me just under 25 mph
Is that what you want?
jaretj
I’ve used that calculator myself, but I have some qualms about it. I’ve noticed that both that calculator and the one at Analytic Cycling (referenced by another poster) indicate that 150 watts would yield me around 21 mph on a windless, flat course. But the calculator from the Computrainer manual (http://www.computrainer.com/.../workout/Table2.html) indicates that the same wattage would result in a speed of only 19 mph (or slightly slower if interpolate my 126-lb weight). I have no idea what the assumptions are behind the Computrainer chart, but that seems to be a very large discrepancy. I find similar discrepancies at other hypothetical wattages. It’s hard to account for, unless the Computrainer manual is assuming that one is riding a fat-tire bike and sitting straight up on the seat (!).
Unfortunately, since I don’t have a power meter, I don’t know what power I’m putting out on the road, so I can’t test out which of these results is the most realistic. Yet I’d really like to have a better handle on what kind of speeds I might attain on the roads from the wattages I put out in my Computrainer intervals.
Fortunately at my job, we are supposed to break things (I blow up tanks for a living).
…smartass! ; ^ )
Yes!!!
And thanks to others for the calculators.
Thanks everyone. It looks like an increase of 25watts at FTP will yiled ~1mph. Thats what I wanted to know.
Thanks everyone. It looks like an increase of 25watts at FTP will yiled ~1mph. Thats what I wanted to know.
I’m not sure thats correct… sounds too liner.
The triathlon calculator now does some correlation between power and speed. You input CP20 watts and it estimates wattage and speed for a given bike distance (as part of a tri) and training intensities. You can work that backward and figure out what power corresponds to a given speed.
I’m not sure thats correct… sounds too liner.
Technically it would be representative of the tangent on the graph of where my FTP is now.
IOW, an additional 23 watts may get me 1mph. 27 more watts may get me another 1mph. Beyond that I don’t really care because I don’t expect my FTP to increase by more than 50 watts in the next year. At that point I’ll re-asses.
ok… It just that 1mph increments are not created equally… You don’t need a power meter to tell you there is a big difference going to 20 mph from 19 vs 25 from 24.