Date:         Tue, 16 Mar 2010 15:39:49 -0400
Reply-To:     Mike S <mikes@FLATSURFACE.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Mike S <mikes@FLATSURFACE.COM>
Subject:      Re: Revs per mile , was: 15" VS. 16' WHEELS
Comments: To: John Bange <jbange@GMAIL.COM>
In-Reply-To:  <6da579341003161126g56e55937kc2f233c21007a467@mail.gmail.co m>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 02:26 PM 3/16/2010, John Bange wrote...
> > I am wanting to know what the revs per mile of the Michelin
> Agilles >205/65R15 C is
>I use this calculator:
>
>http://www.miata.net/garage/tirecalc.html

That calculator is way off with regard to rev/mile. It might be useful
in comparing two different sizes, but not actual tires, since the only
measurement of a real tire which can be expected to be exact is rim
diameter. A tire with a section width of 210 may be called a 215,
because 210 isn't a standard size.

The problem with that calculator, and others I've seen, is that it
figures diameter mathematically, assuming perfect circles, etc. A real
world tire has a rolling radius which is smaller than that of a tire
represented as a perfect circle (it compresses when loaded), which
means it will turn faster.

So where that calculator says a 215/60R16 does 771 revs/mile, Falken
says their ZE-912 of the same size does 808. That's about a 5%
difference.