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01-09-2005, 09:05 PM
| #91 (permalink) |
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Posts: n/a
| Re: Rim brake heat and clincher blowoff, was Re: Potential good newsfor Mt. Washington access. [Only registered and activated users can see links. ] wrote: > Benjamin Lewis writes: > > [FK wrote:] >>>>When you do this, please compare with a static pressure test of the >>>>same tire and rim at room temperature. > > >>>What do you mean by this. Inflation pressure is inflation pressure >>>whether the wheel is rotating or not. > > >>Are you saying that tire blow off depends only on pressure and not >>on temperature? The test Frank proposes could confirm this. > > > As I mentioned, rims reach their peak temperatures quickly on steep > descents and we don't have problems because these are transients. Rim > temperatures drop rapidly as soon as the brake is released if the road > is fairly straight and allows cooling speeds. Treacherous roads are > steep ones that require nearly continuous braking. > > The problem with a static test is that I believe wheel rotation may > have an influence on how predictably the tire releases, there being > constant motion between rim and tire. This is evident from the wear > marks in the rim and the presence of a chafing strip on the tire bead > at that interface. This is a continuation of a somewhat spirited discussion that took place about a month ago on r.b.tech. IIRC, at that time, several people pointed out that room temperature, stationary tires can withstand very high (over 160 psi) pressures without blowoff, and that therefore blowoffs must be caused by something other than _just_ the pressure increase from the heat of braking. I was certainly one who felt that way. Others (I'll let Jobst say who) seemed to be claiming that the only relevant factor was the pressure increase. Thus, after Jobst determines pressure at blowout during hard braking, I'd like to see the same rim subjected to a room temperature static test at the same pressure. We'll then know if _only_ pressure causes those blowouts. It's an opportunity to learn. -- -- --------------------+ Frank Krygowski [To reply, remove rodent and vegetable dot com, replace with cc.ysu dot edu] |
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01-09-2005, 09:05 PM
| #92 (permalink) |
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Posts: n/a
| Re: Rim brake heat and clincher blowoff, was Re: Potential good newsfor Mt. Washington access. [Only registered and activated users can see links. ] wrote: > Benjamin Lewis writes: > > [FK wrote:] >>>>When you do this, please compare with a static pressure test of the >>>>same tire and rim at room temperature. > > >>>What do you mean by this. Inflation pressure is inflation pressure >>>whether the wheel is rotating or not. > > >>Are you saying that tire blow off depends only on pressure and not >>on temperature? The test Frank proposes could confirm this. > > > As I mentioned, rims reach their peak temperatures quickly on steep > descents and we don't have problems because these are transients. Rim > temperatures drop rapidly as soon as the brake is released if the road > is fairly straight and allows cooling speeds. Treacherous roads are > steep ones that require nearly continuous braking. > > The problem with a static test is that I believe wheel rotation may > have an influence on how predictably the tire releases, there being > constant motion between rim and tire. This is evident from the wear > marks in the rim and the presence of a chafing strip on the tire bead > at that interface. This is a continuation of a somewhat spirited discussion that took place about a month ago on r.b.tech. IIRC, at that time, several people pointed out that room temperature, stationary tires can withstand very high (over 160 psi) pressures without blowoff, and that therefore blowoffs must be caused by something other than _just_ the pressure increase from the heat of braking. I was certainly one who felt that way. Others (I'll let Jobst say who) seemed to be claiming that the only relevant factor was the pressure increase. Thus, after Jobst determines pressure at blowout during hard braking, I'd like to see the same rim subjected to a room temperature static test at the same pressure. We'll then know if _only_ pressure causes those blowouts. It's an opportunity to learn. -- -- --------------------+ Frank Krygowski [To reply, remove rodent and vegetable dot com, replace with cc.ysu dot edu] |
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01-09-2005, 09:05 PM
| #93 (permalink) |
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Posts: n/a
| Re: Rim brake heat and clincher blowoff, was Re: Potential good newsfor Mt. Washington access. [Only registered and activated users can see links. ] wrote: > Benjamin Lewis writes: > > [FK wrote:] >>>>When you do this, please compare with a static pressure test of the >>>>same tire and rim at room temperature. > > >>>What do you mean by this. Inflation pressure is inflation pressure >>>whether the wheel is rotating or not. > > >>Are you saying that tire blow off depends only on pressure and not >>on temperature? The test Frank proposes could confirm this. > > > As I mentioned, rims reach their peak temperatures quickly on steep > descents and we don't have problems because these are transients. Rim > temperatures drop rapidly as soon as the brake is released if the road > is fairly straight and allows cooling speeds. Treacherous roads are > steep ones that require nearly continuous braking. > > The problem with a static test is that I believe wheel rotation may > have an influence on how predictably the tire releases, there being > constant motion between rim and tire. This is evident from the wear > marks in the rim and the presence of a chafing strip on the tire bead > at that interface. This is a continuation of a somewhat spirited discussion that took place about a month ago on r.b.tech. IIRC, at that time, several people pointed out that room temperature, stationary tires can withstand very high (over 160 psi) pressures without blowoff, and that therefore blowoffs must be caused by something other than _just_ the pressure increase from the heat of braking. I was certainly one who felt that way. Others (I'll let Jobst say who) seemed to be claiming that the only relevant factor was the pressure increase. Thus, after Jobst determines pressure at blowout during hard braking, I'd like to see the same rim subjected to a room temperature static test at the same pressure. We'll then know if _only_ pressure causes those blowouts. It's an opportunity to learn. -- -- --------------------+ Frank Krygowski [To reply, remove rodent and vegetable dot com, replace with cc.ysu dot edu] |
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01-09-2005, 09:18 PM
| #94 (permalink) |
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Posts: n/a
| Re: Rim brake heat and clincher blowoff, was Re: Potential good newsfor Mt. Washington access. Frank Krygowski wrote: > [Only registered and activated users can see links. ] wrote: > >> Benjamin Lewis writes: >> >> > [FK wrote:] > >>>>> When you do this, please compare with a static pressure test of the >>>>> same tire and rim at room temperature. >> >> >> >>>> What do you mean by this. Inflation pressure is inflation pressure >>>> whether the wheel is rotating or not. >> >> >> >>> Are you saying that tire blow off depends only on pressure and not >>> on temperature? The test Frank proposes could confirm this. >> >> >> >> As I mentioned, rims reach their peak temperatures quickly on steep >> descents and we don't have problems because these are transients. Rim >> temperatures drop rapidly as soon as the brake is released if the road >> is fairly straight and allows cooling speeds. Treacherous roads are >> steep ones that require nearly continuous braking. >> >> The problem with a static test is that I believe wheel rotation may >> have an influence on how predictably the tire releases, there being >> constant motion between rim and tire. This is evident from the wear >> marks in the rim and the presence of a chafing strip on the tire bead >> at that interface. > > > This is a continuation of a somewhat spirited discussion that took place > about a month ago on r.b.tech. IIRC, at that time, several people > pointed out that room temperature, stationary tires can withstand very > high (over 160 psi) pressures without blowoff, and that therefore > blowoffs must be caused by something other than _just_ the pressure > increase from the heat of braking. I was certainly one who felt that way. > > Others (I'll let Jobst say who) seemed to be claiming that the only > relevant factor was the pressure increase. > > Thus, after Jobst determines pressure at blowout during hard braking, > I'd like to see the same rim subjected to a room temperature static test > at the same pressure. We'll then know if _only_ pressure causes those > blowouts. It's an opportunity to learn. There still needs to be a control for temperature in the static test, since of course compressing air into the tire raises the temperature of the air and casing. However, if the tire is inflated slowly, actual temperature rise will be insignificant. In addition to the motion between the tire and rim that Jobst Brandt mentions as possibly affecting blow-off pressure, there is the effect of heating the tire, since the rubber will change properties with temperature. -- Tom Sherman - Near Rock Island |
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01-09-2005, 09:18 PM
| #95 (permalink) |
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Posts: n/a
| Re: Rim brake heat and clincher blowoff, was Re: Potential good newsfor Mt. Washington access. Frank Krygowski wrote: > [Only registered and activated users can see links. ] wrote: > >> Benjamin Lewis writes: >> >> > [FK wrote:] > >>>>> When you do this, please compare with a static pressure test of the >>>>> same tire and rim at room temperature. >> >> >> >>>> What do you mean by this. Inflation pressure is inflation pressure >>>> whether the wheel is rotating or not. >> >> >> >>> Are you saying that tire blow off depends only on pressure and not >>> on temperature? The test Frank proposes could confirm this. >> >> >> >> As I mentioned, rims reach their peak temperatures quickly on steep >> descents and we don't have problems because these are transients. Rim >> temperatures drop rapidly as soon as the brake is released if the road >> is fairly straight and allows cooling speeds. Treacherous roads are >> steep ones that require nearly continuous braking. >> >> The problem with a static test is that I believe wheel rotation may >> have an influence on how predictably the tire releases, there being >> constant motion between rim and tire. This is evident from the wear >> marks in the rim and the presence of a chafing strip on the tire bead >> at that interface. > > > This is a continuation of a somewhat spirited discussion that took place > about a month ago on r.b.tech. IIRC, at that time, several people > pointed out that room temperature, stationary tires can withstand very > high (over 160 psi) pressures without blowoff, and that therefore > blowoffs must be caused by something other than _just_ the pressure > increase from the heat of braking. I was certainly one who felt that way. > > Others (I'll let Jobst say who) seemed to be claiming that the only > relevant factor was the pressure increase. > > Thus, after Jobst determines pressure at blowout during hard braking, > I'd like to see the same rim subjected to a room temperature static test > at the same pressure. We'll then know if _only_ pressure causes those > blowouts. It's an opportunity to learn. There still needs to be a control for temperature in the static test, since of course compressing air into the tire raises the temperature of the air and casing. However, if the tire is inflated slowly, actual temperature rise will be insignificant. In addition to the motion between the tire and rim that Jobst Brandt mentions as possibly affecting blow-off pressure, there is the effect of heating the tire, since the rubber will change properties with temperature. -- Tom Sherman - Near Rock Island |
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01-09-2005, 09:18 PM
| #96 (permalink) |
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Posts: n/a
| Re: Rim brake heat and clincher blowoff, was Re: Potential good newsfor Mt. Washington access. Frank Krygowski wrote: > [Only registered and activated users can see links. ] wrote: > >> Benjamin Lewis writes: >> >> > [FK wrote:] > >>>>> When you do this, please compare with a static pressure test of the >>>>> same tire and rim at room temperature. >> >> >> >>>> What do you mean by this. Inflation pressure is inflation pressure >>>> whether the wheel is rotating or not. >> >> >> >>> Are you saying that tire blow off depends only on pressure and not >>> on temperature? The test Frank proposes could confirm this. >> >> >> >> As I mentioned, rims reach their peak temperatures quickly on steep >> descents and we don't have problems because these are transients. Rim >> temperatures drop rapidly as soon as the brake is released if the road >> is fairly straight and allows cooling speeds. Treacherous roads are >> steep ones that require nearly continuous braking. >> >> The problem with a static test is that I believe wheel rotation may >> have an influence on how predictably the tire releases, there being >> constant motion between rim and tire. This is evident from the wear >> marks in the rim and the presence of a chafing strip on the tire bead >> at that interface. > > > This is a continuation of a somewhat spirited discussion that took place > about a month ago on r.b.tech. IIRC, at that time, several people > pointed out that room temperature, stationary tires can withstand very > high (over 160 psi) pressures without blowoff, and that therefore > blowoffs must be caused by something other than _just_ the pressure > increase from the heat of braking. I was certainly one who felt that way. > > Others (I'll let Jobst say who) seemed to be claiming that the only > relevant factor was the pressure increase. > > Thus, after Jobst determines pressure at blowout during hard braking, > I'd like to see the same rim subjected to a room temperature static test > at the same pressure. We'll then know if _only_ pressure causes those > blowouts. It's an opportunity to learn. There still needs to be a control for temperature in the static test, since of course compressing air into the tire raises the temperature of the air and casing. However, if the tire is inflated slowly, actual temperature rise will be insignificant. In addition to the motion between the tire and rim that Jobst Brandt mentions as possibly affecting blow-off pressure, there is the effect of heating the tire, since the rubber will change properties with temperature. -- Tom Sherman - Near Rock Island |
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01-09-2005, 09:18 PM
| #97 (permalink) |
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Posts: n/a
| Re: Rim brake heat and clincher blowoff, was Re: Potential good newsfor Mt. Washington access. Frank Krygowski wrote: > [Only registered and activated users can see links. ] wrote: > >> Benjamin Lewis writes: >> >> > [FK wrote:] > >>>>> When you do this, please compare with a static pressure test of the >>>>> same tire and rim at room temperature. >> >> >> >>>> What do you mean by this. Inflation pressure is inflation pressure >>>> whether the wheel is rotating or not. >> >> >> >>> Are you saying that tire blow off depends only on pressure and not >>> on temperature? The test Frank proposes could confirm this. >> >> >> >> As I mentioned, rims reach their peak temperatures quickly on steep >> descents and we don't have problems because these are transients. Rim >> temperatures drop rapidly as soon as the brake is released if the road >> is fairly straight and allows cooling speeds. Treacherous roads are >> steep ones that require nearly continuous braking. >> >> The problem with a static test is that I believe wheel rotation may >> have an influence on how predictably the tire releases, there being >> constant motion between rim and tire. This is evident from the wear >> marks in the rim and the presence of a chafing strip on the tire bead >> at that interface. > > > This is a continuation of a somewhat spirited discussion that took place > about a month ago on r.b.tech. IIRC, at that time, several people > pointed out that room temperature, stationary tires can withstand very > high (over 160 psi) pressures without blowoff, and that therefore > blowoffs must be caused by something other than _just_ the pressure > increase from the heat of braking. I was certainly one who felt that way. > > Others (I'll let Jobst say who) seemed to be claiming that the only > relevant factor was the pressure increase. > > Thus, after Jobst determines pressure at blowout during hard braking, > I'd like to see the same rim subjected to a room temperature static test > at the same pressure. We'll then know if _only_ pressure causes those > blowouts. It's an opportunity to learn. There still needs to be a control for temperature in the static test, since of course compressing air into the tire raises the temperature of the air and casing. However, if the tire is inflated slowly, actual temperature rise will be insignificant. In addition to the motion between the tire and rim that Jobst Brandt mentions as possibly affecting blow-off pressure, there is the effect of heating the tire, since the rubber will change properties with temperature. -- Tom Sherman - Near Rock Island |
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01-09-2005, 09:29 PM
| #98 (permalink) |
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Posts: n/a
| Re: Rim brake heat and clincher blowoff, was Re: Potential good news for Mt. Washington access. Tom Sherman writes: > There still needs to be a control for temperature in the static > test, since of course compressing air into the tire raises the > temperature of the air and casing. However, if the tire is inflated > slowly, actual temperature rise will be insignificant. > In addition to the motion between the tire and rim that Jobst Brandt > mentions as possibly affecting blow-off pressure, there is the > effect of heating the tire, since the rubber will change properties > with temperature. I don't believe inflating a tire makes enough temperature difference to worry about. I have not noticed hot tires from inflation nor even a hot hose or brass hose-to-valve coupler (hose chuck). I am aware of Silca frame fit pump heads getting hot in the hand while pumping but that is a big difference from a floor pump and hose. I think we are scraping at nits. Besides, who gives a damn how much pressure a stationary wheel can hold. We are interested in safely riding down steep grades. Jobst Brandt [Only registered and activated users can see links. ] |
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01-09-2005, 09:29 PM
| #99 (permalink) |
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Posts: n/a
| Re: Rim brake heat and clincher blowoff, was Re: Potential good news for Mt. Washington access. Tom Sherman writes: > There still needs to be a control for temperature in the static > test, since of course compressing air into the tire raises the > temperature of the air and casing. However, if the tire is inflated > slowly, actual temperature rise will be insignificant. > In addition to the motion between the tire and rim that Jobst Brandt > mentions as possibly affecting blow-off pressure, there is the > effect of heating the tire, since the rubber will change properties > with temperature. I don't believe inflating a tire makes enough temperature difference to worry about. I have not noticed hot tires from inflation nor even a hot hose or brass hose-to-valve coupler (hose chuck). I am aware of Silca frame fit pump heads getting hot in the hand while pumping but that is a big difference from a floor pump and hose. I think we are scraping at nits. Besides, who gives a damn how much pressure a stationary wheel can hold. We are interested in safely riding down steep grades. Jobst Brandt [Only registered and activated users can see links. ] |
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01-09-2005, 09:29 PM
| #100 (permalink) |
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Posts: n/a
| Re: Rim brake heat and clincher blowoff, was Re: Potential good news for Mt. Washington access. Tom Sherman writes: > There still needs to be a control for temperature in the static > test, since of course compressing air into the tire raises the > temperature of the air and casing. However, if the tire is inflated > slowly, actual temperature rise will be insignificant. > In addition to the motion between the tire and rim that Jobst Brandt > mentions as possibly affecting blow-off pressure, there is the > effect of heating the tire, since the rubber will change properties > with temperature. I don't believe inflating a tire makes enough temperature difference to worry about. I have not noticed hot tires from inflation nor even a hot hose or brass hose-to-valve coupler (hose chuck). I am aware of Silca frame fit pump heads getting hot in the hand while pumping but that is a big difference from a floor pump and hose. I think we are scraping at nits. Besides, who gives a damn how much pressure a stationary wheel can hold. We are interested in safely riding down steep grades. Jobst Brandt [Only registered and activated users can see links. ] |
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