Indeed, and given the relationships between load, width, and pressure, I suspect how wide is wide enough depends on weight (of the rider that is). I am much shorter and roughly 65lbs lighter than you (which is about 30% less) and I run 32mm tires down around 55 or 65 psi. these days. Decades ago I went from riding garden variety 27" clinchers at ~80 psi to hand made 700c tubulars at 100+psi. The tubulars were way more comfortable. I only ever got one pinch flat riding tubulars, and that event also ruined the wheel. So we want to use lower pressure for more comfort (and per Jan less suspension losses), to avoid pinch flats many riders then need bigger tires, which in turn need to have even lower pressure to stay comfortable, which hopefully doesn't then lead to still getting pinch flats. Add to that questions of hysteresis losses in the casing, and changing contact patch shapes and sizes, and you have a complex system. I think some of the admonitions I read about what is true and or has been proven about bike tires over simplify things, and/or are over broad. I will be surprised if "optimal" tire width and pressure are not related to load (unless it turns out any optimum is so weak that it hardly matters what you use).
Does anybody else remember Jobst asserting back in the early 90s that tubulars were slower than clinchers because of the glue? I think the "... flattening was more pronounced in tubulars than clinchers." that Tim mentions was part of his reasoning. 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. > Interestingly in the old Avocet tests, that flattening was more pronounced > in tubulars than in clicnhers. Those were also- as far as I know- the > first published tests hinting at lower RR with wider tires. > > Tire pressure needs to be high enough to prevent pinch flats. At my > weight (6'4" and roughly 220 lbs these days, more in midwinter when I am > not riding due to snow, ice and cold) I pretty much have to run tires 32 mm > or narrower at the top end of the rated pressure on the rear, and run the > same at the front for no particular reason. At 23 mm I have to run them at > 120 psi or lose weight... ;-) Interestingly enough the comfort of my > 559x32 Paselas at 100 psi is very similar to my 700x25 Paselas at 115. > > > > On Jan 5, 2014, at 7:29 AM, Jan Heine <[email protected] <javascript:>> > wrote: > > On Saturday, January 4, 2014 10:59:41 PM UTC-8, ted wrote: >> >> Are you equating the behavior of high performance 32mm clinchers and 25mm >> tubulars, or are both tires you mention clinchers? >> > > I am just talking about test results. We tested the Grand Bois clinchers, > as well as the Vittorias as clinchers and tubulars at a multitude of > pressures. The results were the same - ultra-high-pressures don't provide > any benefit, even on very smooth roads. For more information, I recommend > you read the original article - there are dozens of pages on tire > performance in that issue (Vol. 11, No. 3), much more than I can summarize > in this format. > > 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] <javascript:>. > To post to this group, send email to [email protected]<javascript:> > . > 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 [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.
