In article
>,
"Tim M." > wrote:

> On Sep 15, 12:24*pm, Alan Baker > wrote:
> > In article >, Don Q wrote:
> > > On 2010-09-09 20:50:12 -0400, Arye > said:
> >
> > > > My thinking is to go up one size (from 185/60R14 to 195/60R14), to
> > > > compensate for the slightly too-slow speedometer
> >
> > > Is there a typo here?
> >
> > > I'm no expert but my understanding is that 185 and 195 indicate the
> > > tread width in millimeters. In other words, you are getting a tire that
> > > is about 2/5 of an inch wider. This may provide slightly better grip in
> > > cornering, everything else being equal. (Tread pattern, compound
> > > hardness, tire pressure, slip angles...)
> >
> > > But since they are both 60 profile I think the diameter will be exactly
> > > the same, hence the speedo/odo will not be affected.
> >
> > Ummmm... ...no.
> >
> > The "60" indicates that the section height of the tire is 60% of the
> > section width of the tire (the "185" or "195" in the size; which is not
> > tread width, BTW), and both of these figures are nominal and not
> > necessarily completely precise.
> >
> > So a 185/60R14 tire is (nominally!) 185mm wide at its widest point (the
> > tread is narrower and (nominally!) 2 * (185 * .6)/25.4 + 14 = 22.74"
> > tall.
>
> In fact, there is a great variance from manufacturer to manufacturer
> and from tire model to tire model. On the company "Tire Rack"'s site,
> you can compare the specifications of tires, and see that some tires
> two full metric sizes apart (typically 20mm, or about 4/5's of an
> inch) will have the same tread width, and the smaller section width
> tire may even have greater tread width in some rare instances.

Yup. But all other things being equal, the narrower section width will
typically have the narrower tread.

--
Alan Baker
Vancouver, British Columbia
<http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>