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#41
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Road tire life span
Cheg Nospam writes:
So how do you tell if one tire handles better than another? You test it on a machine. I originally performed such tests on a 16ft long paved plywood tiltbed increasing the angle until the bicycle slid. This was done at low speed and with protective clothing. There was a difference among tires tested. That was a few years ago. If you don't like people replying to your posts, a newsgroup may not be the best place to spend your time. So your position is that no rider can tell the difference between the way different tires handle during normal riding and that they can be distinguished only at low speed on a machine. Perhaps you should both start by defining "handle" in this context. If it is strictly lateral load bearing capacity while rolling, then direct measurement would be the way to go. If it includes other characteristics, eg. vibration transmssion, then the measurement is not sufficient by itself. The term "handling" is adequately defined by use in the tire business and it concerns itself with maneuverability in cornering and for cars how well the tire tracks straight ahead. Ride comfort is another matter. Jobst Brandt |
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#42
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Road tire life span
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#43
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Road tire life span
wrote in message ... Cheg Nospam writes: The term "handling" is adequately defined by use in the tire business and it concerns itself with maneuverability in cornering and for cars how well the tire tracks straight ahead. Ride comfort is another matter. Seems like it would be more clear to call it "cornering traction" or something like that for tires. Handling applied to vehicles is much more complex, dependent on weight distribution, stiffness, steering geometry, drag, etc., as well as traction. Can't do much about traditional usage, I guess. |
#44
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Road tire life span
Cheg Nospam writes:
The term "handling" is adequately defined by use in the tire business and it concerns itself with maneuverability in cornering and for cars how well the tire tracks straight ahead. Ride comfort is another matter. Seems like it would be more clear to call it "cornering traction" or something like that for tires. Handling applied to vehicles is much more complex, dependent on weight distribution, stiffness, steering geometry, drag, etc., as well as traction. Can't do much about traditional usage, I guess. TIRES! Not vehicles. This is about tires and that is extra simple for road bicycle tires. Hnadling being how well the tire performs in curves, nothing more. Jobst Brandt |
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#46
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Road tire life span
Rick Onanian writes:
How do you whether one tire handles better than another since traction is either there or not on pavement. There is no tire squeal or side-slip although writers to this newsgroup sometimes describe their cornering as drifting in curves. This does not occur. Besides that, chip seal, the most abrasive, roads have poorer traction than concrete or hot-mix asphalt roads. This may be all true in a perfect world where roads are fresh, clean pavement. I, however, experienced a controllable side-slip on my rear tire, followed by whole-bike drift, while doing some 35 mph downhill, around a curve, on an older road whose pavement is probably imperfect (probably not as flat a surface as a taut string, for example), and it was probably not perfectly clean. If it was pavement with no sand or other solid (lubricant) I am reasonably sure that you did not drift around a curve on pavement. None of the best bicycle riders in this area believe that this is possible either nor does the tire testing machine that displays sudden and irrecoverable break out while determining maximum lean angle. I was kinda zoned out, pedalling with all my might, when I felt it, and before I processed that information, I found I was on the wrong side of the road; slowing down brought back the missing traction. No accident resulted, but I did get quite scared. I am sure you experienced loss of traction but it was not on clean dry pavement, that condition where cornering ability of a tire can only be assessed by measurement at the moment of break out and crashing. That is not a reasonable thing to attempt and that is why I asked how handling of one tire over another under similar conditions is assessed. It was very exciting, and if I thought I could purposely duplicate it without an accident, I'd love to. I have experienced such slips often and even done so crossing smooth paint stripes in the rain, but I don't attribute those incidents to the tire but rather to sand on the road or a slick wet spot. We ARE talking about handling ability of one tire over another. In a later message, Jobst wrote: You test it on a machine. I originally performed such tests on a 16ft long paved plywood tiltbed increasing the angle until the bicycle slid. I suspect that the different compounds, as well as tire casing constructions, react differently to the changing conditions of a road while moving than to the static conditions of a stopped bicycle on a tilted platform. Per my example above, where I theorize that the pavement is probably slightly wavy (although I've never noticed it, a tire on a 35 mph bike would), the tire's casing would have quite an effect on how the tire's tread stays in contact with the road. Who's talking about static condition? The test bed was ridden across at about 15mph. That is dynamic enough to give a reading and to differentiate between slick tires of that time and ones with a raised center ridge. Bicycle tires do not generate enough heat to have any effect on traction. If they did, you would be able to feel it after making a hard stop from, say, 30mph on a flat road. That is more work than a tire does when cornering because all the weight is on the front wheel and the retardation is close to that of hard cornering. The casing also must compensate for imbalanced wheels. We don't balance our wheels because it doesn't bother us; but if you lift your bike, hold it in your hand, and pedal the rear wheel up to 25 mph, you may feel the bike jumping up and down. Mine does; I taped weights to the wheel until it was balanced, just to see if I could. I suppose it could be something odd with the bearings... I guess you missed the balance experiments that were done by placing lead weights at one spoke location and other such balance and imbalance conditions that are used as excuses for all sorts of rider errors. This has all been done. None of the best descenders I have talked to has ever considered balanced tires as a benefit. Additionally, that test is certainly irrelevant for lateral traction; it only tests fore-aft traction. Sideways, the tire bends (again, involving the casing), and also the rider leans, exposing a different part of the tire to the road. I think you are not visualizing what occurs when a bicycle leans in a curve. The tire testing machine leaned the tire that was loaded in-plane onto a large paved drum while a set of sensors triggered the recording of the angle at which the wheel slipped out. This was repeatable and was done at about 20mph. There are no side loads any more than there are side loads on a bicycle when cornering. Later still, Jobst wrote: TIRES! Not vehicles. This is about tires and that is extra simple for road bicycle tires. Handling being how well the tire performs in curves, nothing more. Then what makes you think your tilt-brake-slide test is relevant to this thread? The test was cornering and that alone and was repeatable. Even though the in situ test at 40mph was made, the limit was not exceeded: http://tinyurl.com/2gbsj Then, Carl did his best to determine what Jobst is trying to say: So your position is that no rider can tell the difference between the way different tires handle during normal riding and that they an be distinguished-- --without pain and destruction-- --only at low speed on a test bed. If, in fact, that is a correct translation, then I disagree I disagree also because that is not a correct translation. In a subsequent reply I reiterated what I said and meant. Maybe you can take that up and tell me how you assess the handling differences between similar sized tires of different manufacture under similar conditions. By this I do not mean a singular anecdote in which a certain tire did thus and so with no comparison. I disagree that a rider can't tell; and more importantly, if I'm wrong and the only way to know how a tire handles is to wipe out, then it would seem _very_ important to know how the tire handles before buying it; at that point, one's life could depend on a tire's handling ability. Could you explain what this paragraph means with respect to a rider being able to feel that one tire handles better than another? My statement is that since road tires (without knobs) do not have a transition point on smooth dry pavement, riders who claim that a tire handles well are merely repeating advertising copy, because below the slip out limit (the only difference) no difference in handling is noticeable. Again, handling being control in curves. Jobst Brandt |
#47
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#48
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Road tire life span
Rick Onanian writes:
This may be all true in a perfect world where roads are fresh, clean pavement. I, however, experienced a controllable side-slip on my rear tire, followed by whole-bike drift, while doing some 35 mph downhill, around a curve, on an older road whose pavement is probably imperfect (probably not as flat a surface as a taut string, for example), and it was probably not perfectly clean. If it was pavement with no sand or other solid (lubricant) I am reasonably sure that you did not drift around a curve on pavement. It probably was not perfect, fresh, clean, 100% black, unmolested pavement. I'm sure that it includes some dust and dirt. Many driveways on that street are dirt. No dirt was visible on the pavement, but it wasn't the 100% dark jet black of brand new pavement either. I'm not quibbling about common dust on roads. The dry pavement you describe fits the definition of clean dry pavement and on such a surface, no "drifting" or sliding is possible without crashing. This has been measured often enough and we have not seen anyone who can demonstrate a slide in a curve since the lean angle for that is greater than 45 degrees to the pavement. At that angle, no one I or any of the fastest descenders that I know have seen anyone do that and not crash. In short, it's a real world condition. It doesn't take that much definition. I am sure you experienced loss of traction but it was not on clean dry pavement, that condition where cornering ability of a tire can only be assessed by measurement at the moment of break out and crashing. Agreed. It was a real road, the kind where bicyclists depend on tire traction. That is not a reasonable thing to attempt and that is why I asked how handling of one tire over another under similar conditions is assessed. Your paved-drum/leaned-bike experiment sounds like a reasonable, if imperfect, test method for fictional roads made of perfectly clean and perfectly flat pavement. I rarely find roads like that, and when I do, the new-pavement fumes make riding somewhat unpleasant. Maybe you can explain what is "imperfect about this test. We have a few riders in this area who corner at the limit of near 45 degrees and the testing machine predicts break out at 47 or so with slick tread repeatably. I have experienced such slips often and even done so crossing smooth paint stripes in the rain, but I don't attribute those incidents to the tire but rather to sand on the road or a slick wet spot. We ARE talking about handling ability of one tire over another. Yes, but what good is it to know the handling ability on perfect pavement when we don't ride on such surfaces? We ride on roads with a bit of sand or a slick wet spot. Knowing the handling ability of a tire for such conditions is immensely more useful. Let's not get into philosophy. You claim to have slid tires on clean dry pavement and I said that is not a recoverable condition so it cannot be the criterion for handling among different tires. We generally don't ride beyond the limit of traction so the criterion must be something else. I'm trying to get to the bottom of how you can give comparative ratings to tires of similar size, inflation and essentially smooth tread. You test it on a machine. I originally performed such tests on a 16ft long paved plywood tiltbed increasing the angle until the bicycle slid. I suspect that the different compounds, as well as tire casing constructions, react differently to the changing conditions of a road while moving than to the static conditions of a stopped bicycle on a tilted platform. Per my example above, where I theorize that the pavement is probably slightly wavy (although I've never noticed it, a tire on a 35 mph bike would), the tire's casing would have quite an effect on how the tire's tread stays in contact with the road. Who's talking about static condition? The test bed was ridden across at about 15mph. That is dynamic enough to give a reading and to I think I understand; the bed was tilted sideways while you rode across it, leaning to the high side of the bed to keep yourself plumb. That makes more sense; I visualized you on the non-moving bike holding the brakes as the front of the bed raised (in a dumping motion), until the bike slid. I didn't lean, I rode across it upright. The test bed was tilted. When the tilt was too steep, the bicycle slid out unrecoverably as it does on a road. The casing also must compensate for imbalanced wheels. We don't balance our wheels because it doesn't bother us; but if you lift your bike, hold it in your hand, and pedal the rear wheel up to 25 mph, you may feel the bike jumping up and down. Mine does; I taped weights to the wheel until it was balanced, just to see if I could. I suppose it could be something odd with the bearings... I guess you missed the balance experiments that were done by placing lead weights at one spoke location and other such balance and imbalance conditions that are used as excuses for all sorts of rider errors. This has all been done. None of the best descenders I have talked to has ever considered balanced tires as a benefit. Well, then we're not talking about a lot of precision here. Wheel imbalance can bounce a bike up and down in my hand at 20mph; that lifting/weighting force must affect the tire's load (and therefore, contact patch) each revolution. I doubt that. Having descended at more than 50mph often without having balanced wheels, I have not felt so much as a hint of imbalance from my conventional wheels that are not balanced. Besides that, as I said, I have done balance and imbalance tests with no perceptible effect and reported the results here. These tests were done to prove that shimmy is not related to wheel im/balance. Additionally, that test is certainly irrelevant for lateral traction; it only tests fore-aft traction. Sideways, the tire bends (again, involving the casing), and also the rider leans, exposing a different part of the tire to the road. I think you are not visualizing what occurs when a bicycle leans in a curve. The tire testing machine leaned the tire that was loaded in-plane onto a large paved drum while a set of sensors triggered the recording of the angle at which the wheel slipped out. This was repeatable and was done at about 20mph. There are no side loads any more than there are side loads on a bicycle when cornering. A different portion of the tread, supported differently by the sidewalls, is in contact with the road. However, the tire testing machine of which you speak, and of which I was unaware in my previous message, would test that. I don't understand what you propose here. The tires tested were typical of available major brand tires. I disagree that a rider can't tell; and more importantly, if I'm wrong and the only way to know how a tire handles is to wipe out, then it would seem _very_ important to know how the tire handles before buying it; at that point, one's life could depend on a tire's handling ability. Could you explain what this paragraph means with respect to a rider being able to feel that one tire handles better than another? A rider can tell if he got through his favorite curve (which has real-world pavement) at a higher speed without any traction reduction. Yes? How do you determine "traction reduction". This is what is at the root of this subject and I propose that you cannot sense this without exceeding the limit and crashing. Therefore, claiming that one tire handles better than another is an undefined subjective claim. More importantly, however, you've failed to address the big issue -- if tires really do break out without any warning as you say, then it would seem extremely important to be able to choose a tire based on it's actual tested and reviewed handling. A high speed traction failure accident sure sounds dangerous! I doubt I would have ridden home if my slip incident turned into a complete loss of control; at 35 mph or so, I would have wrapped my body around a tree or a stone wall (the two types of object found on the side of that road). -- I repeat, you didn't slip on clean dry pavement. I don't claim that you didn't slip but it was for some reason other than traction limitation of the tire. It was more likely some foreign object on the road or a spot of some lubricant. Tire testing machinery is important in this business and as far as I can tell no one has one other than Avocet, a company that is not currently performing such tests. Jobst Brandt |
#49
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Road tire life span
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#50
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Road tire life span
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