That's known as the loaded radius. It is this deflection that limits a tires carrying capacity and speed.

Dennis

Sent from my Windows Phone
________________________________
From: Alan Felder
Sent: 10/15/2011 7:26 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: tire circumference

My two cents:

A tire under load has a smaller effective diameter than one laying on its
side.

--
Alan Felder
Austin TX
82 Diesel Westy

On Fri, Oct 14, 2011 at 12:39 PM, Rob <becida@comcast.net> wrote:

> At  10/14/2011 06:41 AM, Robert Mac Dowell wrote:
>
>> Let me rephrase that. How many RPM'S should it be for the speedo to be
>> right
>>
>
> I've been using http://www.1010tires.com/**tiresizecalculator.asp<http://www.1010tires.com/tiresizecalculator.asp>to
> see sizes, revs & all that stuff for different sized tires.
>
>
>
> Rob
> becida@comcast.net
>