"just ride" On Jan 5, 2014 8:45 PM, "ted" <ted.ke...@comcast.net> wrote:
> Jan, > > You wrote: > "Low and very high pressures were marginally more efficient than > medium-high pressures." > If I read that right, you are saying that your data shows a local maxima > at medium-high pressure with lower losses at tire pressures both above and > below that point. Is that really what you mean to be saying? > > Assuming that you are not really saying the curve is flipped I agree with > Tim, whether the insignificant but measurable change in resistance due to > going from 100psi to 140psi is positive or negative it is still > insignificant and the results are generally speaking pretty much consistent. > > If you really mean the shape of the curve is flipped, then I don't think > your results pass basic sanity checking and maybe you should revisit your > margin of error assessment. > > On Sunday, January 5, 2014 3:21:42 PM UTC-8, Jan Heine wrote: >> >> >> >> On Sunday, January 5, 2014 8:32:54 AM UTC-8, Tim McNamara wrote: >>> >>> Interestingly that is pretty much in keeping with the traditional >>> rolling resistance tests done in tire labs. The decrease in rolling >>> resistance "flattens out" as inflation pressure increases. Even on a steel >>> roller, an increase from 100 to 140 psi doesn't reduce rolling resistance >>> that much. >>> >> >> All the steel drum tests don't measure the suspension losses, even though >> they are a very important part of the equation. >> >> Our tests on real roads with a rider on board found that the curve didn't >> just flatten, but it was U-shaped (if you disregard the really low >> pressures). Low and very high pressures were marginally more efficient than >> medium-high pressures. So the curve looks fundamentally different from that >> you find in steel drum tests. If you believed that data, you'd still gain a >> small advantage going from 100 to 140 psi. In real life, you might actually >> be slower at 140 psi. (Where the least efficient point in the curve is >> depends on the tire type.) >> >> Similarly, on real roads, the "tubular disadvantage" is much smaller >> because tubulars are more comfortable and thus have lower suspension >> losses. This counteracts to a large degree the slightly higher hysteretic >> losses or glue creep or whatever it is that makes them less efficient on >> the steel drum. >> >> Jan Heine >> Editor >> Bicycle Quarterly >> www.bikequarterly.com >> >> Follow our blog at www.janheine.wordpress.com >> > -- > You received this message because you are subscribed to the Google Groups > "RBW Owners Bunch" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to rbw-owners-bunch+unsubscr...@googlegroups.com. > To post to this group, send email to rbw-owners-bunch@googlegroups.com. > Visit this group at http://groups.google.com/group/rbw-owners-bunch. > For more options, visit https://groups.google.com/groups/opt_out. > -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to rbw-owners-bunch+unsubscr...@googlegroups.com. To post to this group, send email to rbw-owners-bunch@googlegroups.com. Visit this group at http://groups.google.com/group/rbw-owners-bunch. For more options, visit https://groups.google.com/groups/opt_out.
