# Tire Size

Grant Lenahan glenahan at vfemail.net
Mon Feb 16 10:33:30 PST 2015

```Well, its wrong, but no as wrong as i stated. The numbers we have discussed here have wandered all over the map in the course of the discussion.

The difference between 215/55-16 and 215/65-16 (only change: aspect ratio) is 6.7%, which rounds to 7%

One complication is that one must convert inches to millimeters or vice-versa to get meaningful answers.

Grant
On Feb 16, 2015, at 1:22 PM, Ed Kellock <ekellock at gmail.com> wrote:

> I have used this for years to compare  tire sizes...
>
> On Feb 16, 2015 6:28 AM, "Grant Lenahan" <glenahan at vfemail.net> wrote:
> How did you get 6%? My math says >8%
>
> c= 2*pi*R
>
>
> Grant
> On Feb 16, 2015, at 12:42 AM, <ekellock at gmail.com> <ekellock at gmail.com> wrote:
>
> > The speedo difference would be 6% which means an indicated 75 is actually 80mph.
> >
> >
> > Ed
> >
> >
> >
> >
> >
> >
> > From: Vincent Gelinas
> > Sent: ‎Saturday‎, ‎February‎ ‎14‎, ‎2015 ‎2‎:‎59‎ ‎PM
> > To: quattro at audifans.com
> >
> >
> >
> >
> >
> > Hi, all.
> >
> > To update, it seems like I had a bad tire. I put the spare on and it all went away. I need four new tires now and I got them for free (almost new Goodyear Extra Grip Ice) but they're 215/65/16 instead of 215/55/16. That's less than an inch difference in  diameter if my math is right (10% of 215 mm is 21.5mm... 21.5mm is around 0.84 inches).
> >
> > I know this will cause my speedometer and odometer to read a little slow, but I'm wondering if it will fit under a stock suspension on a 2004 A6qA. C5 chassis. My research points to yes, but I would like the group's opinion.
> >
> > I would get the correct size, but beggars can't be choosers.
> >
> >
> > Vinney
> >
> > Sent from my iPhone
> > _______________________________________________
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> > http://www.audifans.com/kb/List_information
>
> <TireWheelCombinationCalculator.htm>

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