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 [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/rbw-owners-bunch. For more options, visit https://groups.google.com/groups/opt_out.
