Frontal area A, drag coefficient Cd, Drivetrain loss

Feature Requests
1

Is it possible to calculate from power, speed and elevation:
-Frontal area A,
-Drag coefficient Cd,
-Drivetrain loss?
Unlike here:
https://www.gribble.org/cycling/power_v_speed.html

2

You forgot about the opposing wind. Without wind measurements your error will be extremely large. Consider two riders riding with the same speed one after another. Naturally they apply very different power that depends a lot on the weather conditions.

If you had a wind sensor, you’d get basically a PowerPod that I use calculate the power. In conjunction with a Direct Force Power Meter, you could do what you want.

3

So basically, you want to reverse what the model is doing? How would/could that work?

Anyway, I’ve tried Best Bike Split a few times. Even if you know all parameters - A being particularly hard to calculate correctly - you will still be dependent on weather conditions and form of the day, which makes it near impossible to calculate an end result. The error margin increasing every extra mile / km.

To inverse that, after you have completed your course, is impossible, without additional measuring or establishing other variables, as Andrii mentioned. For example for wind, varying grades and terrain, surface conditions.

4

I have no idea :slight_smile: I’m just suggesting :slight_smile: Maybe only virtual parameters without the wind, average for the whole workout. I just don’t know if it would be useful :slight_smile:

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5

Well, Best Bike Split does try this, if you give them data from an actual ride. It will come up with the parameters you look for, but as I said, the error margin is considerable and I have never been able to get reliable predictions.

So, I guess that working the other way around, is a dead end.

BTW, BBS is not free, although you can use it without paying, with the limitation of one setup, or something like that.

6

yes there are a number of ways, basically if you have all variables but one missing (eg CDA is unknown) then you can calculate it fairly precisely. BUT if you have multiple missing variables then you either have to guestimate some to estimate the truly missing one or control some of them. For example, you can do a climb and use VAM or our calculation (fft.tips/climb) to work out power from the slope and time. Drivetrain loss is difficult to measure exactly and its usually fudged in these calculations…but you can get a pretty good ball park from our drivetrain loss calculation (fft.tips/drivetrain). Don’t forget that wind conditions have a huge effect when cycling solo so take that into account too. We do have a calculator of CDA that takes into account wind, but thats getting pretty detailed for most people.

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