As I mentioned in another note, we disabled inch support in our CAD equipment.
Our drawing to the wheel manufacturer would be metric. We would simply
multiply those two inch dimensions by 25.4. Now they are metric and we can
draw it.
We would require QC and SPC data in the units of our drawing and compared to
our tolerances (there is also an engineering spec.). We do not care what
additional drawings the manufacturer uses to make the part internally.
Also note that many bolt circles are mysteriously integer multiplies of 25.4
mm. Wheels and tires are a mess. There is an association, I think called the
Tire and Rim Association that handles the standards of how tires fit rims. The
real issue is the details of the bead seat and flange design. Note the detail
drawings for the three standard designs. Metric diameter tires imply a very
different bead seat design.
--- On Fri, 3/13/09, Jeremiah MacGregor <[email protected]>
wrote:
> From: Jeremiah MacGregor <[email protected]>
> Subject: Re: [USMA:43753] Re: Tyre (tire) sizes
> To: [email protected], "U.S. Metric Association" <[email protected]>
> Date: Friday, March 13, 2009, 10:54 PM
> I noticed on the top of page three that the rim
> designations are stated in inches on the left but the
> offset and pitch diameter are given in millimeters, also on
> page four other actual dimensions are in rounded
> millimeters only. So what happens if the actual
> manufactured dimensions don't equal the stated inch
> sizes?
>
> So how would you judge rims? As English because the
> designations are in inches or as metric because the actual
> manufacturing units are in millimeters?
>
> Jerry
>
>
>
>
> ________________________________
> From: John M. Steele <[email protected]>
> To: U.S. Metric Association <[email protected]>
> Sent: Friday, March 13, 2009 8:58:39 PM
> Subject: [USMA:43753] Re: Tyre (tire) sizes
>
>
>
>
> You might want to check out this Toyo Tire Talk article, as
> a Japanese company explains wheels.
> http://www.toyojapan.com/tires/pdf/TTT_12.pdf
>
> Rim diameter and width ar specified in inches. The
> details of different flange designs are detailed in metric,
> and the offset and bolt circle are specified in metric.
>
> It wouldn't surprise me if the manufacturing drawings
> are actually metric, and the nominal sizes are multiplied by
> 25.4 mm/in in producing the drawings. It is VERY unlikely
> a company would use mixed units on manufacturing drawings.
> Sure trouble.
>
>
> --- On Fri, 3/13/09, Jeremiah MacGregor
> <[email protected]> wrote:
>
> > From: Jeremiah MacGregor
> <[email protected]>
> > Subject: [USMA:43737] Re: Tyre (tire) sizes
> > To: "U.S. Metric Association"
> <[email protected]>
> > Date: Friday, March 13, 2009, 7:40 PM
> > I'm not sure I understand you. Aren't the
> present
> > standard of tires fully metric? For example, if you
> go to
> > the factory where they are made, aren't all of the
> > drawings and production done completely in metric?
> If you
> > are referring to the rim diameter still given inches,
> does
> > that carry more weight then the way it is produced?
> >
> > If you have a so-called 15 inch tire that is made to a
> 380
> > mm dimension in the factory then can the tire be
> considered
> > a metric dimension. What about the bolts and nuts
> that
> > hold the wheel to the rim? What standard are they
> today?
> >
> >
> > I say if a tire is metric in design and manufacture,
> then
> > it is a metric tire no matter what name you put on it
> for
> > the consumers.
> >
> > Jerry
> >
> >
> >
> >
> > ________________________________
> > From: John M. Steele
> <[email protected]>
> > To: U.S. Metric Association <[email protected]>
> > Sent: Monday, March 9, 2009 8:26:16 AM
> > Subject: [USMA:43590] Re: Tyre (tire) sizes
> >
> >
> >
> > Pat,
> > In fact the metric rim tires are an example of
> "just
> > because it is metric doesn't mean it is
> wonderful."
> >
> > There are whole standards behind those tire labelling
> > schemes; those standards dictate many dimensions on
> both
> > tire and wheel (mostly to ensure it seats and seals
> > properly). The metric rim tire had a new (novel?)
> bead
> > seat design (there were also symmetric ones used in
> > Europe). The bead seat design didn't work out so
> well,
> > the tires gave VERY poor service, and were
> expensive.
> > Owners were SO mad they generally mounted new
> (conventional)
> > wheels and tires, causing sales to go to near zero,
> leading
> > to withdrawal from the market.
> >
> > This does NOT mean that specifying a rim in
> millimeters
> > would be bad. But someone would have to write a new
> > standard behind the labelling scheme, using a more
> > conventional bead seat design and sell the whole
> concept.
> > The exercise apparently left a bad taste and no one
> has
> > every written a new standard for metric rims.
> >
> >
> > --- On Sun, 3/8/09, Pat Naughtin
> > <[email protected]> wrote:
> >
> > > From: Pat Naughtin
> > <[email protected]>
> > > Subject: [USMA:43582] Tyre (tire) sizes
> > > To: "U.S. Metric Association"
> > <[email protected]>
> > > Date: Sunday, March 8, 2009, 11:58 PM
> > > Dear All,
> > >
> > > Apparently, engineers in the 1970s saw an
> opportunity,
> > > through metrication, to rationalise some of the
> > original
> > > design faults in tyre design and construction.
> Here is
> > a
> > > quote from:
> > >
> >
> http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=46
> > > Tires and wheels that have a rim diameter
> expressed in
> > > millimeters (190/65R390, as well as, 365 and 415)
> are
> > called
> > > millimetric sizes. Michelin initiated millimetric
> > sizes for
> > > their TRX tires that saw limited use on many
> different
> > car
> > > models in the late 1970s and 1980s.
> > >
> > > Michelin PAX System run flat tires have been
> > introduced as
> > > an integrated wheel/tire system on a very limited
> > basis as
> > > Original Equipment (O.E.) in North America. An
> example
> > PAX
> > > System size of 235/710R460A 104T expresses tire
> and
> > wheel
> > > dimensions in millimeters (235 mm Section Width,
> tire
> > > Overall Diameter of 710 mm and a 460A mm rim
> diameter,
> > with
> > > the "A" in 460A signifying these tires
> > feature
> > > "asymmetric" beads in which the outside
> bead
> > (450
> > > mm) and inside bead (470 mm) are actually
> different
> > > diameters.
> > >
> > > All of these "unique" tire/wheel
> diameters
> > were
> > > developed specifically because the tire and wheel
> > design or
> > > intended vehicle use required them to be
> different
> > than
> > > conventional tires and wheels. All of these tires
> and
> > wheels
> > > feature bead profiles that have a different shape
> than
> > > traditional "inch rim" sizes.
> > >
> > > Although the millimetric sizes were later
> withdrawn
> > from
> > > the market, they left their legacy in the
> branding on
> > the
> > > side of the tyre. When you see something like:
> > >
> > > 225/50R16
> > >
> > > You know that the tyre is 225 millimetres wide;
> 50 %
> > of
> > > this width (113 mm high from rime to outside
> > diameter); it
> > > is a radial tyre; and it is 16 inches (exactly
> 406.4
> > mm) in
> > > diameter from rim to rim.
> > >
> > > By doing this only 2 of the 3 measurements are
> metric
> > and
> > > not hidden from the public; the third is also
> metric
> > and
> > > hidden from the public. Clearly the opportunity
> was
> > lost to
> > > rethink the design of wheels and tyres to allow
> for
> > the
> > > increased speeds that have occurred since Henry
> > Ford's
> > > days as chief engineer. For example, asymmetric
> beads
> > on the
> > > rims could be useful.
> > >
> > > Cheers,
> > >
> > > Pat Naughtin
> > >
> > > PO Box 305 Belmont 3216,
> > > Geelong, Australia
> > > Phone: 61 3 5241 2008
> > >
> > > Metric system consultant, writer, and speaker,
> Pat
> > > Naughtin, has helped thousands of people and
> hundreds
> > of
> > > companies upgrade to the modern metric system
> > smoothly,
> > > quickly, and so economically that they now save
> > thousands
> > > each year when buying, processing, or selling for
> > their
> > > businesses. Pat provides services and resources
> for
> > many
> > > different trades, crafts, and professions for
> > commercial,
> > > industrial and government metrication leaders in
> Asia,
> > > Europe, and in the USA. Pat's clients include
> the
> > > Australian Government, Google, NASA, NIST, and
> the
> > metric
> > > associations of Canada, the UK, and the USA.. See
> > > http://www.metricationmatters.com for more
> metrication
> > > information, contact Pat at
> > > [email protected] or to get the
> free
> > > 'Metrication matters' newsletter go to:
> > > http://www.metricationmatters.com/newsletter to
> > subscribe.
