Why does speed seem so high?

[ergvideo]

A few people have asked "Why does the speed seem so high, like 22mph when I am only doing (for example) 130W? I can't do that out on the road."

The best way to understand that is "oh, yes you can, and you DO when the resisting forces against you are small, say, as in a tailwind or in a draft, or downhill". Please read the "erg mode vs. 3d Mode" entry and come back to this article.

Now, when the CompuTrainer's magnets are off (such as when the power set-point is below the power dissipated by the pure rolling resistance component), the actual resistive forces are low. Assuming a press on calibration of 2.00, at about 18mph you are dissipating, depending on the tire, about 130W...I could be a bit off. With higher press on, it may show 150W at same speed, since the CompuTrainer is calculating the power lost to rolling drag only. This really is like riding a tailwind, since the only resistance is in the rolling. Try pedaling out on the road downhill or with a very strong tailwind at 200W someday, you will find you go VERY VERY VERY fast. The point is, when the major resistive forces are all low, it is easy to go fast on very low power.

Why do you normally go slower at 130W out on the flat road? Because there are more resistive forces...aerodynamic ones, and the OTHER wheel's rolling friction, to name the first two that come to mind. Now consider a massive headwind if you still don't get it. At 130W, you will go much SLOWER again.

So now go back to the ErgVideo case where power setpoint may show 0% and you are still pedaling furiously at 22 mph and see only 130W, well, you are only working against rolling friction (there is no simulation of wind or terrain changes, strictly power setpoint control).

When ErgVideo is showing low power, it is because our rider was coasting or resting, and you really should too. Again, pedal as lightly as the CT allows. If you do drop under set-point, the CT will kick on and bring you back in line. Many people continue to hammer during 0% periods, and then wonder why the overall video is sooo hard. Well dude, you didn't take recovery when you could have. Take the rest, and this will allow you to sustain the hard efforts longer at at higher power than if you are not taking the recovery periods.

I hope that is somewhat clear. It all means that SPEED in this simulation is irrelevant. The workout will last the same amount of time whether you go at 20 mph or 30mph. The bottom line is that distance nor speed is measured as anything that contributes to the simulation. (But the CT is most accurate between 14-26mph, so going 40 will skew your true power readings a little).

to put a finer point on it: If you go 20 mph and complete a 1 minute long interval. If you go 30mph, how long will it take to complete the 1 minute interval?

Trick question. Since distance is not measured, nor is speed. Now read the question again "how long will it take to complete a 1 minute interval"... One minute!

Suppose the power set-point in both cases was 300W? ie, you do a 1 minute interval at 20mph with power set-point 300W. Now do it at 30mph and 300W for 1 minute. What's different?

Nothing except the resistive force that the CT exerted against the faster wheel vs the slower wheel. It kept the Torque x speed PRODUCT the same (after a small adjustment for rolling friction), and you expended 300W both times for a full minute. If in the same gear, the only thing you felt was less torque with each stroke in the faster case. Upshot is, you went 300W regardless of the speed.

Thus, speed is irrelevant to you. It is just power to you. Yes the CT uses speed to compute the required torque for the setpoint power, but that is it. you do 300w regardless.

Whew, I hope that is clear.

Paul Smeulders