For The Brain Trust-Tires

willie in mn · Jan 6, 2013

Thread below from yesterday about tire pressure warning systems brought up another conundrum. Does a tire low on pressure actually roll faster than when properly inflated? Bear with me a moment, I say it makes no difference.
Circumference of a circle- For easy figuring let's use 3.1416 for pi, & 40" for the diameter, circumference equals 125.664"
Deflate the same tire so it squishes out to give 38" height. Pi times 38 equals 119.38"
Question is- where did the other 6.284" of tread go?
To end the head scratching, it is still there. Key word in the problem is CIRCLE. When the tire squishes out at the bottom, it is no longer round, not a circle, & the diameter times pi formular does not apply. It has been over 50 years, I don't remember my trig classes, but there is a formula to calculate circumference of a deformed shape.
That's my opinion, & I'm sticking to it.
Willie

McBride · Jan 6, 2013

Willie, Don't tell that to the speed sensor on certian cars that trips the warning when the pressure is low.

onefarmer · Jan 6, 2013

Without doing all the math. A tire low on air has a smaller radius from the center of the tire to the ground. Making an "effectively" smaller diameter and therefore must spin faster to maintain the same MPH down the road.

Dan T in MO · Jan 6, 2013

A tire low on pressure ain't a circle. The length of the tread is the same whether it's at 2 psi or 50 psi.

McBride · Jan 6, 2013

This is going to get good.
Might be better than the oil ones.

Larry NEIL · Jan 6, 2013

Ifn there a squirell on a tree, when you get close he runs to the oppisite side. Ifn you walk 360 degrees around that tree and the squirell always oppisite side, did you walk around the squirell too?

colekicker · Jan 6, 2013

If you put two of the same tires beside each other, one properly inflated and the other lower and roll them down a hill, the properly inflated tire will be faster.
Reason, the difference in air pressure changes the amount of surface contact. The more surface contact, the more rolling resistance.

Anonymous-0 · Jan 6, 2013

more/less pressure = bigger/smaller diameter tire. especially a soft race car tire, them boys fret about it.

McBride · Jan 6, 2013

Well that might depend on if your talking squirells or squirrels. LOL

gene bender · Jan 6, 2013

So just what made you post such a question on a tractor site.

Walt Davies · Jan 6, 2013

When lost air the other day it got real slow until it disintegrated.
Walt

Dr. Walt · Jan 7, 2013

NO, you didn't walk around the squirrel because when the squirrel saw you walk 360 degrees around the tree, he thought you were kind of squirrely and he left and jumped across to another tree.

Hay_Man · Jan 7, 2013

What makes you ask that question on this post, yet there's about 15 other non-tractor related posts on this first page of posts that you haven't asked that question on?

Point is, most of the posts here are not tractor related. So get over it.

willie in mn · Jan 7, 2013

Sorry about that part. Had been downstairs on talers, must have hit the clicker once too often.
Willie

onefarmer · Jan 7, 2013

"So just what made you post such a question on a tractor site. "

Because my tractor has at least four tires!

For The Brain Trust-Tires

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