On Aug 7, 4:33 am, Robert Zeidler <zeidler.rob...@gmail.com> wrote: > To get it absolutely spot on every single time? Likely but not possible.
Humans can be very consistent. When we went to the wind tunnel, we found that a rider can adopt the same position, time and again. The variability in wind resistance for the same rider on the same bike - while pedaling - was on the order of 2-5%. More recently, we worked with a Power Meter on the track. I was surprised that my lap times (at 20 mph) were within 1 second of each other, for a quarter-mile lap. Making sure that there is no wind is easy. We have a wind-speed meter, but even more accurate is observing the leaves on trees around our test track. If they don't move at all, wind speed is less than 0.3 m/s For our roll-down tests, we had two people time the first day, and their times were within 0.3 seconds of each other. Repeat runs of the same tires usually fell within 0.5 seconds - which accounts for all the noise combined. The differences between the fastest tire, a hand- made racing clincher, and the slowest, the Rivendell Nifty-Swifty, were 5 seconds. You can see that we had no difficulty showing that these tires offer different performance. (Total time was 25 - 30 seconds, to the slowest tire rolled about 20% slower than the fastest.) Our method does not allow us to determine minute differences between similar tires. Is the Grand Bois Hetre faster than the Mitsuboshi Trimline? We can't tell. But we can tell tires that are significantly different, like the 25 mm version of the Michelin Pro 2 Race, which is faster than the 23 mm version, which in turn is faster than the 20 mm version. Doing a rigorous statistical analysis allows us to see the limitations of our study. I haven't seen any other cycling-related study that has published their statistical analysis - most don't even bother with repeat measurements. As far as which tire is better - we would never make such a value judgment. We provide the data which tire is faster, and we leave the judgment to the reader. The same is true for all our articles: If we form an opinion, we give you plenty of information that allows you to agree or disagree. Even if you disagree, you will find the information useful in forming your own opinion. Jan Heine Editor Bicycle Quarterly Follow our blog at http://janheine.wordpress.com/ -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To post to this group, send email to rbw-owners-bunch@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
