Cycling Forums - View Single Post - Potential good news for Mt. Washington access.

01-10-2005, 10:01 AM

Benjamin Lewis 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.

> Then shouldn't it help to know as much as possible about what
> factors affect blowoff? In addition to the static case, you could
> ride the bike with increasingly higher pressures, without braking,
> to test your hypothesis that motion between the tire and rim is
> contributory. If temperature as well as pressure were a factor,
> perhaps using a different material for the tire bead would help.

OK. Do it. I'm interested in brake heating and the resulting hazard
of crashing... fatally. You can perform the tests you propose without
instrumentation so what's keeping you from doing so? You could "know
as much as possible about what factors affect blowoff."

Jobst Brandt
jobst.brandt@stanfordalumni.org

01-10-2005, 10:01 AM	#124 (permalink)
jobst.brandt@stanfordalumni.org Guest Posts: n/a	Re: Rim brake heat and clincher blowoff, was Re: Potential good news for Mt. Washington access. Benjamin Lewis 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. > Then shouldn't it help to know as much as possible about what > factors affect blowoff? In addition to the static case, you could > ride the bike with increasingly higher pressures, without braking, > to test your hypothesis that motion between the tire and rim is > contributory. If temperature as well as pressure were a factor, > perhaps using a different material for the tire bead would help. OK. Do it. I'm interested in brake heating and the resulting hazard of crashing... fatally. You can perform the tests you propose without instrumentation so what's keeping you from doing so? You could "know as much as possible about what factors affect blowoff." Jobst Brandt jobst.brandt@stanfordalumni.org