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#11
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Fat tire riders look like "fat heads."
On 7/4/2020 10:21 PM, Jeff Liebermann wrote:
https://en.wikipedia.org/wiki/Rolling_resistance Rolling_resistance = CRF * Normal_force where CRF is the coefficient of rolling friction. CRF is determined by the road and tire materials and construction. It doesn't change with inflation pressure. I think that's an oversimplification, at least if we want to be practical about bicycle tires. I think bike tires are a special case. And this has been discussed since the days of Jobst. Resistance to a bike's forward motion on level ground is usually thought of as having three components: Mechanical friction in bearings, chain, etc., which is small; Aerodynamic drag, which dominates at higher speeds but is minimal at casual biker's or most mountain biker's speeds; and rolling resistance, which is usually thought of as the simple formula above, CRF * Normal_force and is mostly due to hysteresis and internal friction in the tire itself, plus some scrubbing action against the road. (Heavy sidewalls and anything beyond minimal tread increase that internal friction.) But there's another dominant effect, which is the resistance generated by hysteresis inside the rider's body. Jiggling the rider's body tissue generates internal friction loss and heats that tissue. That energy must come from somewhere. It's energy that's not available to move the bike forward, and the more jiggling, the less the bike speed. If you want to decrease CRF * Normal_force, you could of course provide a very hard, smooth surface and a hard, smooth tire. Build a rail bike! Steel wheels on a steel rail have a very low CRF because there is almost no deflection at the contact point, so very little internal friction and hysteresis. But we ride on asphalt, concrete or dirt; and those have bumps. So how about we use very high pressures in our tires to minimize tire flex and its hysteresis losses? Sure, that works - but only on super-smooth surfaces. It's great for wooden velodrome tracks. But on real roads, let alone dirt, it's a disaster. The limit of that approach is to ride an old Hard Tired Safety bike, with non-pneumatic tires and wheels. As Dr. Dunlop and other showed over 100 years ago, a bicyclist if far faster on air. Why? Because even if the Hard Tired Safety reduces the losses where the bike wheel and tire contact the ground, it greatly increases the amount of jiggling in the rider's body. It sends energy into his body instead of into forward motion. Besides, it beats the heck out of him and tires him that way. So maybe we should say bike motions has _four_ types of resistance: tiny mechanical friction, speed-dependent aero drag, rolling resistance due to flex and scrubbing of the tire itself, and body losses caused by jiggling. The last two are related. You want to minimize the total of the two. Ideally, that would be done by choosing the proper tire width, construction and pressure for each road surface. The smoothest surfaces get the narrowest and highest pressure tires, and the roughest get widest and lowest pressure ones. So choose your tires and pressures based on the surfaces you ride. Just avoid super-cheap ones with heavy tread patterns and thick sidewalls. The fashion seems to be changing. I think I have only one friend who still uses 18mm tires with 120+ psi. I never saw any evidence his bike rolled better than mine with 28mm tires. -- - Frank Krygowski |
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#12
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Fat tire riders look like "fat heads."
On 7/5/2020 11:46 AM, Jeff Liebermann wrote:
On Sat, 04 Jul 2020 19:21:20 -0700, Jeff Liebermann wrote: When you take the same rider and bike, and switch from slicks to knobbies, you reduce the ground patch area. That increases the ground pressure, which causes the rolling resistance to increase. That's one reason why riding knobbies on pavement is like dragging an anchor. I forgot to mumble something about tire pressu "Everything You Think You Know About Bicycle Tire Pressure is Probably Wrong" https://www.roadbikerider.com/the-tire-pressure-revolution-by-jan-heine-d1/ Quoting: Tire pressure has almost no effect on a tire’s speed. If lower pressures don’t make tires slower, then you can create wide tires with supple casings. You run them at lower pressures, and you don’t give up any performance on smooth roads. On rough roads, you actually gain speed, because the tire (and you) bounce less. And on all roads, you are more comfortable. Conclusion Tire pressure does not significantly affect your bike’s rolling resistance, but the casing construction of your tires does. This means that you can ride lower pressures without going slower, and that wide tires are no slower than narrow ones - as long as they have similar casings. The fastest tires have supple casings that consume less energy when they flex, and transmit fewer vibrations, creating a win-win situation. These tires roll super-fast no matter at what pressure you run them. So, you have a choice. A hard stiff narrow tire at high pressure or a soft flexible wide tire at low pressure. And there are limits to both. Quick search brings: http://www.money4invest.com/infoshar...s-tire-safety/ and: https://www.researchgate.net/figure/...fig1_268806919 Note thermal image of underinflated tire in 1st link (which is what I searched), heat being energy transfer. -- Andrew Muzi www.yellowjersey.org/ Open every day since 1 April, 1971 |
#13
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Fat tire riders look like "fat heads."
On Sunday, 5 July 2020 13:10:07 UTC-4, Frank Krygowski wrote:
On 7/4/2020 8:21 PM, Rich wrote: On Saturday, 4 July 2020 17:28:28 UTC-4, Andre Jute wrote: On Saturday, July 4, 2020 at 4:21:07 AM UTC+1, Rich wrote: Unless the stupid bike is powered, why endure that ridiculous rolling resistance? You may be inexperienced or a troll, but I've already settled that question, he http://thorncyclesforum.co.uk/index....16360#msg16360 Andre Jute I don't follow the fashion, I create it PS. BTW, you're ill-informed. Low pressure balloons have a lower rolling resistance, so there is no "ridiculous rolling resistance". Where'd you ever pick up that dumb street corner myth? You are complete wrong on this, it's not possible for a tire with a larger contact patch to have lower rolling-resistance than a small, higher inflation tire. Where did you learn physics, grade-school? I know a lot of people on mountain bikes who switched from 2.25" tires to 1.9" to lower rolling resistance. Assertions and "I know a guy" anecdotes without data and links don't get much respect around here. What do you know about mechanical hysteresis? -- - Frank Krygowski Yet a lot of times you use anecdotes about people you know, to try and prove a point. Cheers |
#14
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Fat tire riders look like "fat heads."
On Sunday, July 5, 2020 at 5:46:09 PM UTC+1, Jeff Liebermann wrote:
On Sat, 04 Jul 2020 19:21:20 -0700, Jeff Liebermann wrote: When you take the same rider and bike, and switch from slicks to knobbies, you reduce the ground patch area. That increases the ground pressure, which causes the rolling resistance to increase. That's one reason why riding knobbies on pavement is like dragging an anchor. I forgot to mumble something about tire pressu "Everything You Think You Know About Bicycle Tire Pressure is Probably Wrong" https://www.roadbikerider.com/the-tire-pressure-revolution-by-jan-heine-d1/ Quoting: Tire pressure has almost no effect on a tire’s speed. If lower pressures don’t make tires slower, then you can create wide tires with supple casings. You run them at lower pressures, and you don’t give up any performance on smooth roads. On rough roads, you actually gain speed, because the tire (and you) bounce less. And on all roads, you are more comfortable. Conclusion Tire pressure does not significantly affect your bike’s rolling resistance, but the casing construction of your tires does. This means that you can ride lower pressures without going slower, and that wide tires are no slower than narrow ones - as long as they have similar casings. The fastest tires have supple casings that consume less energy when they flex, and transmit fewer vibrations, creating a win-win situation. These tires roll super-fast no matter at what pressure you run them. So, you have a choice. A hard stiff narrow tire at high pressure or a soft flexible wide tire at low pressure. I'm not surprised, Jeff. Comparing the standard and the lightweight folding Big Apples, and the thinner T19A tubes with the standard T19 tubes for 60x622 tyres, I found the lightweight versions to be very much more comfortable with no degradation in handling and roadholding at the limit, and not more fragile either on my rough but tarmacced lanes. Handling is what the tyre does that is expected in response to normal inputs up to the margin of error, roadholding is recovery from something extreme stupid the rider does (or the road or environment does to him) beyond the margin of error. It must have been a common experience, because elements of the folding Big Apple, and especially its ultra-flexible sidewall, were then spread throughout the Big Apple range by Schwalbe, so that the folding tyre is no longer a separate line within the brand. Andre Jute A life spent on the response of wheeled vehicles is not wasted. Sometimes I wish I continued as a hot rodder all my life. |
#15
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Fat tire riders look like "fat heads."
On Sunday, July 5, 2020 at 5:23:18 PM UTC+1, AMuzi wrote:
On 7/4/2020 4:28 PM, Andre Jute wrote: On Saturday, July 4, 2020 at 4:21:07 AM UTC+1, Rich wrote: Unless the stupid bike is powered, why endure that ridiculous rolling resistance? You may be inexperienced or a troll, but I've already settled that question, he http://thorncyclesforum.co.uk/index....16360#msg16360 Andre Jute I don't follow the fashion, I create it PS. BTW, you're ill-informed. Low pressure balloons have a lower rolling resistance, so there is no "ridiculous rolling resistance". Where'd you ever pick up that dumb street corner myth? Maybe, maybe not. Rolling resistance is a J curve for tires, Maybe true for bicycle tyres, but if true for bicycle tyres, that merely shows they fall on a particular section of the more general S curve that suspension engineers generally gnash their teeth about. A J-curve implies some linearity across a considerable stretch of input/output, and there isn't a huge amount of linearity in rubber and hardwearing fibres and air arranged as tyres with their tubes in service at speed. with extremely narrow and firm tires suffering loss from bounce and excessively wide tires from casing flex. Casing material and thickness, tread material thickness and pattern, inflation pressure and road surface also move that curve's shape and height. There's some optimum width for each rider with each tire design on each road. A racing car and a fast bike are by definition extreme designs which compromise factors non-essential to their stated purpose. Andre Jute Be frightened, be very frightened of what the tyres will do to the beautiful geometry of your suspension design. |
#16
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Fat tire riders look like "fat heads."
On Sunday, July 5, 2020 at 5:58:22 PM UTC+1, Frank Krygowski wrote:
On 7/5/2020 12:23 PM, AMuzi wrote: On 7/4/2020 4:28 PM, Andre Jute wrote:. .... .... +1. It's not simple. -- - Frank Krygowski Hey, at last Franki-boy gets something right. First, he agrees with Mr Muzi, which is always wise, and with me, which is smart for a clown I've taken against because otherwise I'll make a fool of him ever hour on the hour, and then he gives us the safe platitude: "It's not simple." Now he's resting on his laurels... Andre Jute Applause, gentlemen, for Franki-boy getting something right. The opportunity to be nice to him probably won't arise for another year. |
#17
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Fat tire riders look like "fat heads."
Andre Jute wrote:
On Sunday, July 5, 2020 at 5:46:09 PM UTC+1, Jeff Liebermann wrote: On Sat, 04 Jul 2020 19:21:20 -0700, Jeff Liebermann wrote: When you take the same rider and bike, and switch from slicks to knobbies, you reduce the ground patch area. That increases the ground pressure, which causes the rolling resistance to increase. That's one reason why riding knobbies on pavement is like dragging an anchor. I forgot to mumble something about tire pressu "Everything You Think You Know About Bicycle Tire Pressure is Probably Wrong" https://www.roadbikerider.com/the-tire-pressure-revolution-by-jan-heine-d1/ Quoting: Tire pressure has almost no effect on a tire’s speed. If lower pressures don’t make tires slower, then you can create wide tires with supple casings. You run them at lower pressures, and you don’t give up any performance on smooth roads. On rough roads, you actually gain speed, because the tire (and you) bounce less. And on all roads, you are more comfortable. Conclusion Tire pressure does not significantly affect your bike’s rolling resistance, but the casing construction of your tires does. This means that you can ride lower pressures without going slower, and that wide tires are no slower than narrow ones - as long as they have similar casings. The fastest tires have supple casings that consume less energy when they flex, and transmit fewer vibrations, creating a win-win situation. These tires roll super-fast no matter at what pressure you run them. So, you have a choice. A hard stiff narrow tire at high pressure or a soft flexible wide tire at low pressure. I'm not surprised, Jeff. Comparing the standard and the lightweight folding Big Apples, and the thinner T19A tubes with the standard T19 tubes for 60x622 tyres, I found the lightweight versions to be very much more comfortable with no degradation in handling and roadholding at the limit, and not more fragile either on my rough but tarmacced lanes. Handling is what the tyre does that is expected in response to normal inputs up to the margin of error, roadholding is recovery from something extreme stupid the rider does (or the road or environment does to him) beyond the margin of error. It must have been a common experience, because elements of the folding Big Apple, and especially its ultra-flexible sidewall, were then spread throughout the Big Apple range by Schwalbe, so that the folding tyre is no longer a separate line within the brand. Andre Jute A life spent on the response of wheeled vehicles is not wasted. Sometimes I wish I continued as a hot rodder all my life. I tend to notice handling more than slight differences in rolling resistance. Granted I’m not a racer trying to milk milliseconds from my times. But cornering in a tight downhill is something I care about. My HED wheels running 23mm conti folding tire at 90 psi are the sweet spot for me. Comfortable and good handling. Just my two cents but I find the discussion on rolling resistance without handling considered to be a bit useless. |
#18
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Fat tire riders look like "fat heads."
On 7/5/2020 5:41 PM, Duane wrote:
Andre Jute wrote: On Sunday, July 5, 2020 at 5:46:09 PM UTC+1, Jeff Liebermann wrote: On Sat, 04 Jul 2020 19:21:20 -0700, Jeff Liebermann wrote: When you take the same rider and bike, and switch from slicks to knobbies, you reduce the ground patch area. That increases the ground pressure, which causes the rolling resistance to increase. That's one reason why riding knobbies on pavement is like dragging an anchor. I forgot to mumble something about tire pressu "Everything You Think You Know About Bicycle Tire Pressure is Probably Wrong" https://www.roadbikerider.com/the-tire-pressure-revolution-by-jan-heine-d1/ Quoting: Tire pressure has almost no effect on a tire’s speed. If lower pressures don’t make tires slower, then you can create wide tires with supple casings. You run them at lower pressures, and you don’t give up any performance on smooth roads. On rough roads, you actually gain speed, because the tire (and you) bounce less. And on all roads, you are more comfortable. Conclusion Tire pressure does not significantly affect your bike’s rolling resistance, but the casing construction of your tires does. This means that you can ride lower pressures without going slower, and that wide tires are no slower than narrow ones - as long as they have similar casings. The fastest tires have supple casings that consume less energy when they flex, and transmit fewer vibrations, creating a win-win situation. These tires roll super-fast no matter at what pressure you run them. So, you have a choice. A hard stiff narrow tire at high pressure or a soft flexible wide tire at low pressure. I'm not surprised, Jeff. Comparing the standard and the lightweight folding Big Apples, and the thinner T19A tubes with the standard T19 tubes for 60x622 tyres, I found the lightweight versions to be very much more comfortable with no degradation in handling and roadholding at the limit, and not more fragile either on my rough but tarmacced lanes. Handling is what the tyre does that is expected in response to normal inputs up to the margin of error, roadholding is recovery from something extreme stupid the rider does (or the road or environment does to him) beyond the margin of error. It must have been a common experience, because elements of the folding Big Apple, and especially its ultra-flexible sidewall, were then spread throughout the Big Apple range by Schwalbe, so that the folding tyre is no longer a separate line within the brand. Andre Jute A life spent on the response of wheeled vehicles is not wasted. Sometimes I wish I continued as a hot rodder all my life. I tend to notice handling more than slight differences in rolling resistance. Granted I’m not a racer trying to milk milliseconds from my times. But cornering in a tight downhill is something I care about. My HED wheels running 23mm conti folding tire at 90 psi are the sweet spot for me. Comfortable and good handling. Just my two cents but I find the discussion on rolling resistance without handling considered to be a bit useless. +1 -- Andrew Muzi www.yellowjersey.org/ Open every day since 1 April, 1971 |
#19
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Fat tire riders look like "fat heads."
On Sunday, July 5, 2020 at 11:41:11 PM UTC+1, Duane wrote:
Andre Jute wrote: On Sunday, July 5, 2020 at 5:46:09 PM UTC+1, Jeff Liebermann wrote: On Sat, 04 Jul 2020 19:21:20 -0700, Jeff Liebermann wrote: When you take the same rider and bike, and switch from slicks to knobbies, you reduce the ground patch area. That increases the ground pressure, which causes the rolling resistance to increase. That's one reason why riding knobbies on pavement is like dragging an anchor. I forgot to mumble something about tire pressu "Everything You Think You Know About Bicycle Tire Pressure is Probably Wrong" https://www.roadbikerider.com/the-tire-pressure-revolution-by-jan-heine-d1/ Quoting: Tire pressure has almost no effect on a tire’s speed. If lower pressures don’t make tires slower, then you can create wide tires with supple casings. You run them at lower pressures, and you don’t give up any performance on smooth roads. On rough roads, you actually gain speed, because the tire (and you) bounce less. And on all roads, you are more comfortable. Conclusion Tire pressure does not significantly affect your bike’s rolling resistance, but the casing construction of your tires does. This means that you can ride lower pressures without going slower, and that wide tires are no slower than narrow ones - as long as they have similar casings. The fastest tires have supple casings that consume less energy when they flex, and transmit fewer vibrations, creating a win-win situation. These tires roll super-fast no matter at what pressure you run them. So, you have a choice. A hard stiff narrow tire at high pressure or a soft flexible wide tire at low pressure. I'm not surprised, Jeff. Comparing the standard and the lightweight folding Big Apples, and the thinner T19A tubes with the standard T19 tubes for 60x622 tyres, I found the lightweight versions to be very much more comfortable with no degradation in handling and roadholding at the limit, and not more fragile either on my rough but tarmacced lanes. Handling is what the tyre does that is expected in response to normal inputs up to the margin of error, roadholding is recovery from something extreme stupid the rider does (or the road or environment does to him) beyond the margin of error. It must have been a common experience, because elements of the folding Big Apple, and especially its ultra-flexible sidewall, were then spread throughout the Big Apple range by Schwalbe, so that the folding tyre is no longer a separate line within the brand. Andre Jute A life spent on the response of wheeled vehicles is not wasted. Sometimes I wish I continued as a hot rodder all my life. I tend to notice handling more than slight differences in rolling resistance. Granted I’m not a racer trying to milk milliseconds from my times. But cornering in a tight downhill is something I care about. My HED wheels running 23mm conti folding tire at 90 psi are the sweet spot for me. Comfortable and good handling. Just my two cents but I find the discussion on rolling resistance without handling considered to be a bit useless. Yes, that is why my original article at http://thorncyclesforum.co.uk/index....16360#msg16360 considered roadholding (the mannered response of a tyre) and handling (its tolerance for rude inputs) at some length, and then considered comfort ahead of rolling resistance. By comparison, making a mountain out of rolling resistance, as Rich (and of course Franki-boy) try to do, because that is what they feel can understand from the welter of interrelated considerations, is a juvenile descent to triviality. All the same, I clearly put a higher value on comfort than you do, Duane. Anyone for whom 23mm tyres at 90psi are the sweet spot must have an backside of cast iron. Andre Jute Tyres are horses for courses |
#20
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Fat tire riders look like "fat heads."
On 7/5/2020 8:06 PM, AMuzi wrote:
On 7/5/2020 5:41 PM, Duane wrote: Andre Jute wrote: On Sunday, July 5, 2020 at 5:46:09 PM UTC+1, Jeff Liebermann wrote: On Sat, 04 Jul 2020 19:21:20 -0700, Jeff Liebermann wrote: When you take the same rider and bike, and switch from slicks to knobbies, you reduce the ground patch area.* That increases the ground pressure, which causes the rolling resistance to increase.* That's one reason why riding knobbies on pavement is like dragging an anchor. I forgot to mumble something about tire pressu "Everything You Think You Know About Bicycle Tire Pressure is Probably Wrong" https://www.roadbikerider.com/the-tire-pressure-revolution-by-jan-heine-d1/ Quoting: Tire pressure has almost no effect on a tire’s speed. If lower pressures don’t make tires slower, then you can create wide tires with supple casings. You run them at lower pressures, and you don’t give up any performance on smooth roads. On rough roads, you actually gain speed, because the tire (and you) bounce less. And on all roads, you are more comfortable. Conclusion Tire pressure does not significantly affect your bike’s rolling resistance, but the casing construction of your tires does. This means that you can ride lower pressures without going slower, and that wide tires are no slower than narrow ones - as long as they have similar casings. The fastest tires have supple casings that consume less energy when they flex, and transmit fewer vibrations, creating a win-win situation. These tires roll super-fast no matter at what pressure you run them. So, you have a choice.* A hard stiff narrow tire at high pressure or a soft flexible wide tire at low pressure. I'm not surprised, Jeff. Comparing the standard and the lightweight folding Big Apples, and the thinner T19A tubes with the standard T19 tubes for 60x622 tyres, I found the lightweight versions to be very much more comfortable with no degradation in handling and roadholding at the limit, and not more fragile either on my rough but tarmacced lanes. Handling is what the tyre does that is expected in response to normal inputs up to the margin of error, roadholding is recovery from something extreme stupid the rider does (or the road or environment does to him) beyond the margin of error. It must have been a common experience, because elements of the folding Big Apple, and especially its ultra-flexible sidewall, were then spread throughout the Big Apple range by Schwalbe, so that the folding tyre is no longer a separate line within the brand. Andre Jute A life spent on the response of wheeled vehicles is not wasted. Sometimes I wish I continued as a hot rodder all my life. I tend to notice handling more than slight differences in rolling resistance.* Granted I’m not a racer trying to milk milliseconds from my times.* But cornering in a tight downhill is something I care about.* My HED wheels running 23mm conti folding tire at 90 psi are the sweet spot for me.* Comfortable and good handling.** Just my two cents but I find the discussion on rolling resistance without handling considered to be a bit useless. +1 Except rolling resistance is quantifiable, at least to a degree. Handling is a pretty nebulous item. Similarly, I've been skeptical of Jan Heine's testimonies about bikes that "plane" i.e. that have the precise degree of flexibility (not too stiff) that allows the frame to somehow match his pedal strokes and go faster with less effort. like a speedboat that planes over the water. I'm not saying such a thing is impossible; but I'd like some hard evidence "planing" exists other than his rave review. If some bikes "plane" more than others, how can we measure it? Likewise, if one tire "handles" better than others, how can we measure it? Does anyone know if there is an actual metric? -- - Frank Krygowski |
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