The user's guide says:
I have a computrainer, so it doesn't simulate motoring down grade, but I thought that my setting (-2% grade limit) would let me do some pedaling work on the downhill side but still have the effect described above, that is, the speed would be as though I were on the actual grade."Descent grade limit" does not let trainers that are capable of motoring to simulate grades below certain limit but the video still moves with the speed you would be moving if the grade was unclamped.
Last night I rode Grand Alps Part 5, Col de la Bonette which includes a long downhill of about 13.5 miles. On the descent, the on screen speed display never dropped below 30mph and ranged from low 30s to 40+, so I should have been able to easily finish the descent in less than half an hour.
It actually took me about 50 minutes and Strava says that my average speed on the descent was 16.7mph.
I wasn't riding terribly hard so I guess that time and speed are plausible for a -2% grade, but I thought that setting was just to give some resistance and the original video grade would still be in effect. I have noticed this on descents before, but this one was so long it became very obvious that there is a big difference between the virtual speed displayed and the distance covered.
Can you please clarify? Is this working as expected?