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Clinchers vs. Sew-ups
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#82
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Clinchers vs. Sew-ups
On Thu, 06 Oct 2005 17:00:44 GMT,
wrote: Vittoria Mastik One was not around then, from what I can tell. It has been around as long as Vittoria has been in the tubular business. Really? Was it sold under a different name. I never saw it in the major mail order catalogs or the bike shops near where I live more than perhaps 10 years ago. JT **************************** Remove "remove" to reply Visit http://www.jt10000.com **************************** |
#83
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Clinchers vs. Sew-ups
anonymous snipes:
Don't be a jerk, Brandt. I'm not repeating myth and lore, I'm stating something that occured to me and threw out for discussion. Oh? "better shock absorption", "more comfortable ride", "lower rolling resistance" are classics of pro-tubular speak and no quantitative values or explanation how these things are achieved. That is what myth and lore are made of! What an ass. Proposing a hypothesis for discussion is not the same as claiming something to be true; quantitative values are not necessary, and I don't see you providing any, either. Is it possible to discuss this without using rude epithets? The response style suggests weakness of your position and lack of perspective of the concepts involved. No it doesn't. It applies a deserved label to you for your insulting habit of insisting that anyone who questions you about anything, is spouting "myth and lore". What do you mean by "better shock absorption", "more comfortable ride", "lower rolling resistance" and how are these produced by, for instance, glue on the rim. You might notice that outside the transition of tire casing to rim the two kinds of tire are mechanically indistinguishable. Both are constrained to not absorb any road displacements between the rim edges and both have a circular cross section that can be deformed outside of that diameter. It is not irrelevant that they are also visibly indistinguishable, exactly because they are physically identical. The tire "systems" are not physically identical as anyone can see who picks them up and looks at them. Clinchers absorb road displacements to the air inside them beyond the rim edge toward its interior; tubulars practically do not. You make obvious that you do not understand how tires support loads. Has it occurred to you that automotive tire shops mount tires on wheels, inflate them and subsequently put them in place to support the car. You cannot see the difference in pressure on a tire pressure gauge. That is why you can inflate your spare in a car to 30psi to be subsequently used at 30psi when you let the car off the jack. The difference in displacement is hidden inside the casing and the rim. It is absurd to suggest that they are the same simply because you can't see the difference. You say that as though it were a secret or scientific mystery. What is hidden inside the rim? Part of the tube, the bead and part of the sidewall? Yes, and what effect does that have on the parameter you claim are different between clinchers and tubulars? The problem with your treatise there, in addition to being poorly written and lacking "quantitative values", is the failure to demonstrate that the change in pressure is insignificant. You simply say it is and expect me to take your word for it, which is pretty much the same method of argument that you always use, and, ironically, accuse me of using. You present nothing more than lore that may or may not be myth, but there is no way to know. I think you don't understand vector forces and how they can be separated into vertical and horizontal components. I think I do. Please demonstrate that rather than dodging with quips. The analysis of tire casing forces is not a quantitative subject but rather one of forces and their direction. Tire casings do not support wheels in compression or bending but purely in tension, similar to wire spokes in a bicycle wheel. One thing that I'm pretty sure of is that a tire at 100psi does not compress as far toward the rim as one at 50psi, so the air pressure is doing something there that I don't see adequately explained. Read it again if you missed that. Casing tension varies with pressure and rim support is given by casing tension. Or rewrite it so that it is adequately explained. You seem to be the exception when it comes to understanding what keeps a wheel off the ground. I don't believe it needs a rewrite considering how many people understand what it says. If you start with incorrect beliefs and hold to them, you will have difficulty understanding. **** off, Brandt. You don't know how hard I ride. You just explained that you don't get snake bites. I don't know any active riders who have never gotten such a flat and I have seen a lot of them. I don't remember any circumstance where I had a flat on a tubular that I could attribute to compression of the tire to the rim, except for being squeezed once about 25 years ago into a curb by a car. And despite what you say, there are few people on this ng that ride tubulars regularly that have that type of flat with any regularity if at all. It's a stupid argument, regardless, because it's a false dichotomy: you are probably one of only a handfull of people in the world that have an opinion on it that would claim that tubulars and clinchers are equally subject to pinch flats. That arises today because most of the tubular riders don't ride unpaved roads and never get to cobbled streets. As I said, there were no other tires but tubulars for the sport so we rode them wherever we went and in those days many of the great roads in the Alps were yet unpaved. I don't know anyone who rides tubulars today other than at old timers meets where we try to pull out stuff from the old days. So, again, **** off. I see you can't control your emotions. Try to be civil if you want your utterances to be taken seriously. The term snake bite was coined at my Wednesday evening tubular patch sessions in the 1970's when our local racers came to patched flats. We all know the lore of how you supposedly coined the phrase- you've told us over and over again. This only gets repetition when you do as though you never heard of it or understand how it occurs. Which has nothing to do at all with the tall tale about you coining the phrase. You seem to have problems with that. Do you repair tubular tires? I think I said no, or at least very infrequently, anymore, below. However, I have repaired many, many of them. The only tires I remember as having punctures not attributable to outside punctures were some steel (that's right, steel) belted Hutchinsons. Because the problem ONLY occurred with them, and I never bought any more of them, I believe it was a tire design issue, and at the time thought it was likely that impacts were causing tube penetration by wires in the steel belts. I admit it would indicate that with some frequency I do bottom out the tire, yet I don't get pinch flats with the more conventionally designed tubulars. I don't understand what your are proposing here. Are you saying that these people are not capable of measuring rolling drag? They measure it indirectly by doing coast-down testing. As I pointed out, that doesn't give the same information direct drag measurements as a range of inflation pressures do. There is no way you can see what effect inflation pressure has on RR unless it is measured over a range of pressures. Your tests prove what they prove: that with some unknown but admittedly inferior glue and gluing technique (you implied that the gluing technique allowed for easy removal to replace a tire after a flat; and you definitely did not use the best glue available today), some Avocet clincher demonstrated lower rr than some unknown tubular, and that that advantage disappeared with the better bond provided by track shellac. Those are not unknown tubulars. I think your arguments fall in the same bag as the denial that disc brakes pose a hazard as they are designed today. I have no opinion on disc brakes. If the tubulars are not unknown, then you should be able to tell us here the make and model. If you do, I would rephrase my statement thusly: "that with some unknown but admittedly inferior glue and gluing technique (you implied that the gluing technique allowed for easy removal to replace a tire after a flat; and you definitely did not use the best glue available today), some Avocet clincher demonstrated lower rr than a (fill in tubular name) tubular that has been out of production for (fill in number of years out of production) years and whose performance was not quantified by comparison to other tubulars, and that that advantage disappeared with the better bond provided by track shellac." I take it you haven't looked at the data because the tires are all identified on the graph: http://skyscrapercity.com/showthread.php?t=252897 In light of this, I don't understand what your are writing about, not having looked at the graphs that show the tubular offset due to rim losses. The curves clearly show a family of similar curves in which tubulars have the best characteristics (slope of curve and flatness) but are out of place by a constant. These curves are closely related most of them being identical except for a bas multiplier. You seem to believe that tubulars at their peak use had something that could be improved. Can you explain what those features are and how they affect performance? That would be a better question to ask Conti or Vittoria. For me, the answer is I don't know, but would not be willing to make any assumptions that nothing could be improved. You ought to be able to give an answer to that when you have been arguing that case all along by saying that the test values are irrelevant because they were made by older tires. Vittoria Mastik One was not around then, from what I can tell. It has been around as long as Vittoria has been in the tubular business. Vittoria has had glue but Mastik One? If so, did you use it? If you didn't, and I'm pretty sure you used Clement, you used a vastly inferior glue, which goes back to what I already said: you did not quantify the quality of the glue or the gluing technique. I used Tubasti and Pastali, Clement and Pirelli being a lower temperature glue that tended to dry out in time. But 3M should be replaced by Vittoria Mastik One. It has been shown experimentally to be superior to 3M and every other glue used for gluing tubulars in all characteristics that seem to be important for a glue. In what way is it superior. Bond strength, heat resistance, time to achieve ridable bond strength. Go read the test reports. I posted the reference already in this thread. Do you not believe that tubulars move on tacky road glue I don't know whether a tire glued on properly with it would "move" significantly more than shellac. And neither do you, because you didn't test it. You seem to base your disagreement on the use of Vittoria Glue. Is that the only thing you think is germane in this discussion. Is it that the whole subject depends on whether or not the tests were done with this glue? You'll notice that other adhesives are used by the tubular users in this forum. Do you think they have no reasons for doing so? and that this is addressed by using hard glues for timed track events? Sure. And _maybe_ by using the best glues on the road. So if this is not a problem with tubulars, how do you justify the search for the ideal glue, one that is almost inseparable from the tire and rim yet one that allows changing a tire. This indicates to me that there is a problem with gluing them to rims that is worth addressing. What conclusion do you find faulty and why? I already answered that. Repetition wouldn't hurt. I don't recall you giving an answer on that anyway, most of which is in this thread right now. I have not seen any bond strength comparisons. That's because you didn't read the reports that I referenced. Higher bond strength seems not to be desirable because tires cannot be removed non-destructively, as you can read from people damaging base tapes from excessively cured glue. And which we have now determined was probably because they didn't use the best technique for removing the tires, prying up a spot on a tire, working the tool all the way under it, and then working the tool around the rim. Once you get it going you may be able to pull it the rest of the way off by hand, but you have to make sure you are pulling up the base tape, not the casing. It is not that hard, and it is certainly easier than trying to tear off by hand a tire glued on that well. I have NEVER damaged a base tape removing a tire. This sounds arduous. You may recall that quick and easy tire changes is one of the main advantages touted for tubulars. The question is whether a strong soft glue such as Vittoria Mastik One, applied properly with the minimal amount necessary to achieve a secure bond, can approach the performance of shellac, and perhaps even surpass the performance of shellac in your testing (because the shellac performance in your testing may not have been optimized). If it is sticky and elastic it cannot be as low in losses as a hardened adhesive that is hard to the extent of being brittle, as shellac is. Yes, but the difference may not be significant, and unless the shellac was used with perfect technique (whatever that is) there is always the possibility that approaching perfect technique with a soft glue could give better results that you got with the shellac. "MAY NOT". I think you'll have to give more evidence than that. I showed you my data, you show me yours. These tires were mounted by people who knew their business. Wasn't their business clinchers? Their business is tires and tubulars as well. These tests were not done by desk clerks. So it wasn't Avocet, who had a major stake in getting clinchers into the "serious" cycling market? Regardless, it is obvious that they were dependent on tubular myth and lore as opposed to experimentation in their glue and their gluing technique. These tests were performed in Japan by IRC at the time they sponsored racing and served racing teams. I don't really see that anymore, but you present a strong argument for using the minimal amount of glue necessary to provide a strong, secure bond. I don't understand what you mean by that. Are you saying that I propose applying glue in a thick layer before mounting the tire? On the contrary, I am saying that your research suggests that the best way to mount a tire is to minimize the thickness of the glue layer while insuring a strong, secure bond. Yes, go on, and what does that have to do with the rolling resistance cause by the interface between tire and rim. As I pointed out, rims show base tape pattern in the aluminum from this motion. That means that upon heating from braking, the glue migrates out of the highest pressure contact and allows the fabric of the tire to contact the metal. Is that thin enough? As I said, regardless of who mounted the tire and with which rim glue, base tapes wore out and rims showed friction wear in the aluminum. That does not mean that anyone used the best glue or the best technique. You are retreating. The contention is that tubulars mounted on pressure sensitive (tacky) glue have losses. Now you are saying that users are not using your preferred adhesive so the concept is flawed. If you use hardening glue, then there is no rim glue loss. So what? The point is that tubulars glued with the conventional adhesives have rolling losses that make them poorer in RR than the best clinchers. That's all I ride for the last 30+ years except for a very occasional mtb excursion. I don't patch them so much anymore, though; I tend to use Tufo sealant or throw them away. I get very few flats, so this system works for me without being wasteful. How very very very few flats? Throwing away a tire that gets a flat, is wasteful in my perception. I don't throw away a tire that gets a flat, I try to fix it with Tufo sealant which usually works. If it doesn't then I am likely to toss it unless I think it otherwise worth saving. What I am saying is that the combination of few flats and Tufo rarely leaves me in the position of having to repair a flat the traditional way. Please explain what is obsolete. The glue. I think if you read wreck.bike.tech you will see that riders still use the glues furnished by tubular tire manufacturers and these are no different from those used in the past. That doesn't mean they are the best. Just the same, why are you so fixated on glue? Look at the results. The glue is significant variable in the results, but unfortunately you only used two (Clement? & shellac). I never used shellac. I only pointed out that after seeing the test results I finally discovered why there is hard glue. You should realize that until these curves were shown, no one in bicycle racing or the industry could explain why there was hard glue. All they said was that rolling a tire on a track was a greater possibility if hard glue was not used. Do your base tapes wear in the course of riding a tire through to the cords or not? I regularly ride my tires until the cords show, now and in my days on tubulars. Sadly, I don't. Something else catastrophic usually happens first. It seems you may also believe most physics is obsolete, much of the research having been done more than a century ago. Poor Galileo doesn't rate highly in your science! And in fact much of it is obsolete, being usable to provide rough explanations of only phenomena that are directly observable with the human senses. But, of course, this is really beside the point since your comment has no purpose other than to belittle and amuse. I take that as your interpretation of technical explanations of natural phenomena that disagree with your beliefs. No, take it as general relativity changed the understanding of gravity that Galileo and Newton gave us. In an interview with one of Einstein's colleagues the old professor said with irritation "He had no right in publishing his relativity papers because he didn't do the research." This is not an original tactic as you can see. Attack the messenger, not the message. Jobst Brandt |
#84
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Clinchers vs. Sew-ups
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#85
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Clinchers vs. Sew-ups
So, again, **** off.
I see you can't control your emotions. Try to be civil if you want your utterances to be taken seriously. Jobst, you are rewarding his rudeness with a relatively polite reply. Worse, you are engaging him in the discussion without any sort of commitment (from him) to civility. If you don't mind, then fine, but if you keep rewarding him, you can expect more of the same. Tom |
#86
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Clinchers vs. Sew-ups
Tom Reingold writes:
So, again, **** off. I see you can't control your emotions. Try to be civil if you want your utterances to be taken seriously. Jobst, you are rewarding his rudeness with a relatively polite reply. Worse, you are engaging him in the discussion without any sort of commitment (from him) to civility. If you don't mind, then fine, but if you keep rewarding him, you can expect more of the same. I don't write this stuff to please myself but rather to let readers know there is another explanation for what I generally call myth and lore, the stuff without merit that is passed from one generation of bicyclists to the next. The rude responses do two things, they generally invoke the myth that needs airing, and they do it in a way that civilized readers recognize as rude and uninformed of the matter at hand. As I said above, the readers that count can tell the difference. There is only one kind of appropriate reply, regardless of what tone the critic uses, and that is a civil and polite one. Stooping to use a similarly rude response is not constructive. When a subject comes up often enough, I often write a short essay on it and put it in the FAQ so I don't need to write an explanation. Sheldon was kind enough to offer a bit of space for that on his web site: http://www.sheldonbrown.com/brandt/ Jobst Brandt |
#88
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Clinchers vs. Sew-ups
wrote: I think you'll find that a 25mm clincher has the same deflection to bottoming as a 25mm tubular, the only difference are a few 0.001" of casing thickness and tube thickness difference but then clinchers with thin latex tube and the same TPI are around and they are indistinguishable in displacement from tubulars. In fact, it takes a careful eye to see whether a tire is a tubular or clincher unless there is rim glue smeared around. I think you missed what supports a rim off the ground but that can be corrected at: http://www.sheldonbrown.com/brandt/rim-support.html "unit casing tension is equivalent to inflation pressure times the radius of curvature divided by pi. As the curvature reduces when the tire bulges out, the casing tension decreases correspondingly. The inflated tire supports the rim primarily by these two effects." The casing tension is decreased as the tire bulges out in response to an external force. The local loss of tension creates a localized difference in casing tension between that part of the tire and the rest of it, and the pressure acts on the tire as the outside force is dissapated to equalize the tension. So the effect of the pressure is not dependent on some increased pressurization caused be compression of the tire, but by the difference between atmospheric pressure and the pressure inside the tire (which is obviously a much larger difference) acting to restore tension to some state of equilibrium for the tire as a whole. Nevertheless, the compressibility of an inflated tire is dependent on its volume, and two tires of equal "radius" above the rim edge, pressurized to the same degree, will not be equally compressible if the volume of one tire is different from the other. It looks to me like the formula above may be flawed in its use of pi; this would be a reasonably good approximation for a tubular tire, but less so for a clincher where the correct value may be something more complex (and larger), and suggests to me that casing tension may be less in a clincher compared to a tubular of equal pressure, which would completely explain the anecdotal but widely reported difference between clinchers and tubulars in their tendency toward bottoming out. |
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