Revolutions or Counts going Downhill as Compared with going Uphill
Introduction
Pete suggests that riding downhill causes less weight on the front wheel, while the opposite is true for riding uphill. This would mean that riding in the downhill direction on a cal course would give more counts than riding uphill on the same course, and this has, in fact, been observed.
Mark: in the above you misquoted Pete so I have made a correction below.
Pete suggests that riding uphill causes less weight on the front wheel, while the opposite is true for riding downhill. This would mean that riding in the downhill direction on a cal course would give more counts than riding uphill on the same course, and this has, in fact, been observed.
I was surprised at the above statement, because in a casual observation during a course measurement I found that I got fewer revolutions going down a long hill than when going up. I had assumed that this was caused by the tendency to lean forward and push harder on the pedals when going uphill, and so compress the front tire more.
Results
Last night I decided to check my previous observation on a very steep but straight hill, and repeatedly measured the revolutions following the white line on the edge of the road between two marks set 705 meters apart going down and up four times. The first three downhill rides were done at 20-25 mph and the last at 9-10 mph. The first three uphill rides were done at 7-9 mph while seated, and the last at 12-14 mph while standing on the pedals much of the time. Here are the results with all the downhill rides given odd numbers:
1. 337.97
2. 338.17
3. 338.04
4. 338.11
5. 338.02
6. 338.15
7. 338.00
8. 338.51
Downhill, there seems to be no significant difference between any of the rides and the average was 338.01. Evidently using a slower speed made no difference.
Uphill for the first three rides again there was no significant difference between any of them, but the average was 338.14 or plus 0.038% compared with that for the downhill rides, thus confirming my previous observation. The last ride, on which I stood up on the pedals much of the time, was much higher at 338.51 or plus 0.148%.
Differences found by Pete and Mark may have to do with riding posture and the fact Mark has a mountain bike.
Conclusions
1. A calibration course can have an appreciable slope without affecting its accuracy compared with that of a flat course. Uphill rides however should be taken slowly. This conclusion agrees with that of Pete but not with that of Mark.
2. Hills are better measured in the downward direction, but if measured uphill, they should be taken slowly without standing on the pedals.