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Topic: Deflate Gate Footballs and Motorhome Tires (Read 834 times) previous topic - next topic
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Deflate Gate Footballs and Motorhome Tires

Yahoo Message Number: 99231
I'd guess that about now New England football fans are sitting by the window having a beverage, watching the snow fall and wondering how Bill Belichick could be wrong about the 2 lb. pressure change in the footballs. After all, our RV tires go up and down a lot more, maybe as much as 10 lbs. How can the coach be wrong?

 Well, it's related to the percent change in temperature, and the temperature scale required for air (actually all gases) is Kelvin, which uses Absolute Zero (total absence of heat energy. . . as cold as is possible in the universe). That's real cold . . . may hundreds of degrees below zero Fahrenheit! But enough of getting in the science weeds.

Anyway, in the temperature range we're interested in, the pressure change is less than 2% for around 10 degrees Fahrenheit (F). For your 100 PSI coach tires that would be 2 PSI less or 98 PSI for colder tires. For a football at 12 PSI, that's only around 2/10 of a PSI or 0.2 PSI . . . a tenth of the actual drop found with the balls.
 Coach was right though about "pressure should return to the same level when warmed back up," but no one seems to have checked if that was the case. That means the balls were less than 12 PSI to start.

He got it all half right.

Lee (leozbrowski@...) President, CCI

2007 Country Coach Intrigue 12153
CAT C-13

Re: Deflate Gate Footballs and Motorhome Tires

Reply #1 –
Yahoo Message Number: 99235
Lee,

While on this subject: I know you've provided this information before, but I can't find my notes. I know the published psi for our tires is at 65 deg Fahrenheit. Is the actual adjustment 1-1/2 psi  for every 10 degrees change from 65 degrees?

Thank-you,

Fred Compton

2005 magna # 6454

Re: Deflate Gate Footballs and Motorhome Tires

Reply #2 –
Yahoo Message Number: 99237
Hi Fred. It's closer to 2 PSI per 10 degrees F. That's what I use, though a couple PSI one way or the other is no likely to be an issue.

Lee (leozbrowski@...) President, CCI

2007 Country Coach Intrigue 12153
CAT C-13