Tony tonypf11 at gmail.com
Wed Dec 2 10:13:06 CST 2015

Mathematically, circumference is PI times diameter or 3.14159..... times 
the diameter.

On 12/2/2015 11:06 AM, Fred Cisin wrote:
> On Wed, 2 Dec 2015, Paul Koning wrote:
>> Actually, it's the circumference that matters, not the diameter.
> I always thought that there was a relatively stable relationship 
> between those!  :-)
> Circumference tends to be a little over 3 times the diameter (3.0 in 
> some states)    :-)
>> Does the circumference of a rubber roll change significantly when you 
>> press on it?
> If it shifts or squeezes out to the sides, not so much.
> If it compresses, yes.
> Before TPMS, some cars got a crude estimation of low tire pressure by 
> comparing the RPM of a tire (ABS sensors) with its fully inflated 
> brethren.
> (circumference changing with pressure change)

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