hot climate tire pressure rules/science

"czb" <[email hidden]> wrote in message
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Quoted message said:

been riding west of tucson this week. today got a 2.5 hr ride in at
105 degrees. yesterday was about 101. but here's the thing. my tires
are constantly almost flat in the morning. i have pulled the tubes and
run them in water to find leaks. nada. even changed out new tubes to
be sure. rides fine, though appears to lose pressure. running basic
velicoraptor 26.1 i can't locate answer in archives. here's the q:
does extreme heat for several hours tigger later air loss? i would
have thought air inside would have heated up and expanded, so filling
to say 40 psi would on its own by the climate get to 45-50. instead 65
psi becomes 25 overnight. what's up with that? thanks for advice.

First, let me tell you something. That pressure rating is for COLD tire
pressure. that means driven less than 5 minutes or 1 mile (in a car at
least).

A frequent problem people in northern climates have is that they get low
tire pressures in the spring, and high tire pressures in the fall. You are
not loosing air, nor are you gaining it. air is expanding and compressing.
Heat makes air increase in pressure.

What is the tempurature swing? if you are going from 5C(40F) to 30C(90F)
then I would not worry about it.

Micheal

czb said:

been riding west of tucson this week. today got a 2.5 hr ride in at
105 degrees. yesterday was about 101. but here's the thing. my tires
are constantly almost flat in the morning. i have pulled the tubes and
run them in water to find leaks. nada. even changed out new tubes to
be sure. rides fine, though appears to lose pressure. running basic
velicoraptor 26.1 i can't locate answer in archives. here's the q:
does extreme heat for several hours tigger later air loss? i would
have thought air inside would have heated up and expanded, so filling
to say 40 psi would on its own by the climate get to 45-50. instead 65
psi becomes 25 overnight. what's up with that? thanks for advice.

There's nothing about the heat that causes pressure loss. If you're
losing 40psi overnight, you've got a leak. Try pumping up the tubes
more when you're looking for the leak (try getting the diameter of the
tube to 3" or more. My guess is that you've got a thin thorn stuck in
your tire that's going to punch a tiny little hole in every tube you
install.

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $695 ti frame