On 15 Jul 2006 14:50:44 -0700,
[email protected] wrote:
>Hello,
>
>I have, for several years, been riding exclusively on Avocet tires and
>have been very pleased with their performance and flat resistance.
>
>However on a recent ride in hot temperature (~ 105 degree air
>temperature, probably hotter on the pavement), I had 6 flats for 5
>distinct reasons over a couple hundred miles. I noticed also (while
>changing the flats) that the casing felt extremely supple.
>
>The following day, in comparable heat, I switched to a Continental
>Gatorskin, and experienced no flats. The casing also seemed to remain
>stiffer throughout the day.
>
>Has anyone noticed a correlation between high heat and flats on certain
>tires? It seemed to me that the heat could soften the rubber, causing
>it to pick up loose debris on the road more readily.
>
>
>Thanks,
>Sam
Dear Sam,
Unfortunately, a reasonable sample requires thousands of miles on the
same route and dozens of flats (or more). The Gatorskin is probably
just stiffer because it's thicker than whatever Avocet you're using.
Rain is the most commonly noticed correlation between flats and
weather, not heat.
One reason is that a wet front tire flings up far more debris,
increasing the probability that something sharp will be sticking up
dangerously instead of lying harmlessly flat when the rear tire
arrives.
The other reason is that water lubricates debris, reduces friction,
and lets it penetrate the tire more easily. We use rubber tires
because dry rubber has tremendous friction against dry surfaces.
The usual example offered here on RBT is cutting rubber tubing in a
high school lab. Dry tubing requires sawing back and forth with a dry
razor blade because the metal sides encounter more and more friction
as they slice into the rubber.
But if you wet the blade or the tube, you cut through easily with a
single swipe. The water lubricated the blade/rubber interface.
To return to hot weather, it's possible that more bottles are tossed
out windows in summer, just as more mowing operations might scatter
more thorns and debris on the road during the growing season.
For what it's worth, here's my flat tire average by month, going back
for years on the same route where winter rides are 36-45 degrees (to
hell with it when it's colder) and summer rides are over 90 degrees
(and agreeably faster, due to the lowered air density):
total 10 yr
212 avg
jan 7 3.3% 0.8
feb 20 9.4% 2.2
mar 25 11.8% 2.8
apr 17 8.0% 1.9
may 14 6.6% 1.6
jun 19 9.0% 2.1
jul 22 10.4% 2.4
aug 26 12.3% 2.9
sep 16 7.5% 1.8
oct 17 8.0% 1.9
nov 15 7.1% 1.7
dec 14 6.6% 1.6
There's a slight pattern of fewer flats in colder weather, but it's a
little misleading. December and January are cold months with few
flats, but they're also months where I skip more rides.
June, July, and August do seem to support a hot-weather theory, but
those hot months are when I rarely miss a ride, the goatheads are
flourishing, the road crews are mowing the sides of the highway and
bike path, beer-bottle-tossing traffic is higher to the reservoir, and
the gravel pit was busier. Summer is also when it rains here.
Cheers,
Carl Fogel
