I would rather know how wide is wide enough (as opposed to how wide is too wide).
It seems generally accepted that really low pressure results in more rolling resistance than somewhat more pressure does. Somebody (sorry to say I forget the proper citation to credit the appropriate party) did some investigation and concluded that the pressure to achieve 15% drop produced an optimum trade off, with further increases in pressure yielding insignificant reductions in resistance. They then generated curves indicating what pressure was required to produce the chosen 15% drop as a function of load and tire width. If I recall correctly that work presumed that further pressure increases would produce small reductions in resistance but that rider comfort would be compromised and it wasn't worth it to ride harder tires. I think Jan's work shows that (due to suspension losses which he includes in rolling resistance) for real world conditions there will be a true rolling resistance minimum at some optimal pressure for a given combination of road surface, rider, and tire. The point where decreasing losses in the tire itself are offset by increased suspension losses in the rider determining that optimum. I think it is reasonable to postulate that such an optimum pressure would depend on how rough the surface was. I do not know if Jan (or anybody else) has tested that hypothesis.Since narrower tires ride squishier for a given pressure, it also seems likely that such an optimum pressure would be higher for narrower tires. Again I don't know if that hypothesis has ben tested experimentally. The question "does tire a roll faster than tire b" is not really a properly posed question without some assumption about the tire pressure. If we accept Jan's statements about suspension losses it seems assumptions about the road surface (and perhaps the body composition of the rider) may also be necessary. Are the tires to be compared at equal pressure? At 15% drop? At an experimentally determined optimum pressure for a given load and road surface? I think we all assume such comparisons are made with equal load, and that increasing or decreasing the load would not change the relative rankings of the tires (I don't know if anybody has proven that experimentally). What I would like to know is, for me, using tire pressures I find comfy but not overly squishy, how much faster is a Hetre than a Lierre than a Cypres on different sorts of surfaces. I expect the only way to find out is to buy and ride each type myself, because I doubt anybody is going to publish curves of watts per kph as a function of load and tire pressure on a variety of surfaces for each of those tires (with margin of error / uncertainty too of course). It would sure be nice if somebody did though. On Saturday, January 4, 2014 1:17:58 PM UTC-8, Patrick Moore wrote: > > > IIRC, Jan has asked aloud if there is a point where wider might begin to > make a tire slower. Has this been answered? > > Also, has he or anyone else determined that a 23 mm Pro Race 3 is slower > than a 25 mm on a very smooth road? A 19mm? On glass? In brief, is there a > breadth below which an otherwise identical tire is always slower even on > the best of surfaces? On the other hand, is there a point where, even on > rough surfaces, a wider tire is not faster than a narrower one? 60 mm? 70 > mm? 100 mm? > > Will they ride Pugsleys in Paris Roubaix? > > Patrick Moore, asking seriously despite the flippancy, who does plan to > replace his Pro Race 23s with 25s. > > On Sat, Jan 4, 2014 at 1:17 PM, ted <ted....@comcast.net <javascript:>>wrote: > >> >> 2) All other things being equal a wider tire will have lower rolling >> resistance than a narrower one. >> > -- > Burque (NM) > > Resumes that get interviews: > http://www.resumespecialties.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.
