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Tires for a '90 Miata



 
 
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  #11  
Old September 16th 10, 07:03 PM posted to rec.autos.makers.mazda.miata
Tim M.[_2_]
external usenet poster
 
Posts: 49
Default Tires for a '90 Miata

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.
Ads
  #12  
Old September 16th 10, 07:31 PM posted to rec.autos.makers.mazda.miata
Alan Baker
external usenet poster
 
Posts: 2,026
Default Tires for a '90 Miata

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>
  #13  
Old September 16th 10, 07:42 PM posted to rec.autos.makers.mazda.miata
Lanny Chambers
external usenet poster
 
Posts: 832
Default Tires for a '90 Miata

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

> > > But there WAS a typo the I was looking for good thread-wear, not good
> > > thread-ware...

> >
> > [...must...sit...on...hands...]

>
> I was just tinking te same ting....


Ask nicely, and you might get your aitches back.

--
Lanny Chambers
St. Louis, MO
'94C
  #14  
Old September 17th 10, 02:11 PM posted to rec.autos.makers.mazda.miata
Don Q[_2_]
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Posts: 32
Default Tires for a '90 Miata

On 2010-09-15 09:29:30 -0400, Arye > said:

> It's true that that 185 and 195 indicate the tread width. However, the
> 60 indicates the ratio of diameter to width, so it goes up
> proportionally.


Strictly speaking you are correct of course.
However, 60% of 185 versus 60% of 195?

Without going into heavy (for me) math, I will speculate that the
difference in diameter will come to about 2%. If I'm going 51 and my
speedometer is showing 50, I can certainly live with that margin of
error.

cheers



  #15  
Old September 17th 10, 02:37 PM posted to rec.autos.makers.mazda.miata
Grant Edwards[_3_]
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Posts: 68
Default Tires for a '90 Miata

On 2010-09-17, Don Q <Don> wrote:
> On 2010-09-15 09:29:30 -0400, Arye > said:
>
>> It's true that that 185 and 195 indicate the tread width. However, the
>> 60 indicates the ratio of diameter to width, so it goes up
>> proportionally.

>
> Strictly speaking you are correct of course.
> However, 60% of 185 versus 60% of 195?


(195-185)/195 = 5%

> Without going into heavy (for me) math, I will speculate that the
> difference in diameter will come to about 2%. If I'm going 51 and my
> speedometer is showing 50, I can certainly live with that margin of
> error.


Using stock tire sizes, my speedo is off by 8-10% at freeway speeds,
so a 2% correction is hardly worth considering. A 5% correction is
a little better.

--
Grant Edwards grant.b.edwards Yow! What GOOD is a
at CARDBOARD suitcase ANYWAY?
gmail.com
  #16  
Old September 17th 10, 04:40 PM posted to rec.autos.makers.mazda.miata
Frank Berger
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Posts: 286
Default Tires for a '90 Miata

Don Q wrote:
> On 2010-09-15 09:29:30 -0400, Arye > said:
>
>> It's true that that 185 and 195 indicate the tread width. However,
>> the 60 indicates the ratio of diameter to width, so it goes up
>> proportionally.

>
> Strictly speaking you are correct of course.
> However, 60% of 185 versus 60% of 195?
>
> Without going into heavy (for me) math, I will speculate that the
> difference in diameter will come to about 2%. If I'm going 51 and my
> speedometer is showing 50, I can certainly live with that margin of
> error.
>
> cheers


As many do.


  #17  
Old October 4th 10, 09:43 PM posted to rec.autos.makers.mazda.miata
rich[_3_]
external usenet poster
 
Posts: 2
Default Tires for a '90 Miata

I just made that exact tire change you mention on my '99 Miata. I went
to 195/60 14's. I wanted a bigger tire and to get the car off the
ground a little more. And the tires do look better, but the amount it
raised the car is hard to tell getting in and out of it. But I will
say it made a drastic difference in the handling. Not quick and tight
in turns like it was before. It more does a swerve in turns than the
quick instant turns it used to. Now I'm a true believer in short
sidewall height for better handling. I wouldn't go back to the
original tire size on the next set though, I'll be shopping for some
15" or 16" wheels for the next go 'round. It will take me that long to
find bigger wheels I like. Most after market wheels look like total
crap to me, so I'll be looking for the same design that came on the
car in a bigger size if anyone makes them.

On Thu, 09 Sep 2010 20:50:12 -0400, Arye > wrote:

>It's time to replace the Kumhos on my '90 Miata. My thinking is to go up
>one size (from 185/60R14 to 195/60R14), to compensate for the slightly
>too-slow speedometer, and buy a set of four Sumitomo HTR A/S P01.
>
>My questions:
>
>1. Any wise comments on the increased size?
>
>2. Any wise comments on the Sumitomos, or recommendations for a better
>tire choice? I'm looking for a comfortable ride and good thread-ware in
>an all-season (including light snow) tire, not performance.
>
>-- Arye.


  #18  
Old October 7th 10, 01:04 AM posted to rec.autos.makers.mazda.miata
Christopher Muto
external usenet poster
 
Posts: 306
Default Tires for a '90 Miata

On 9/17/2010 9:11 AM, Don Q wrote:
> On 2010-09-15 09:29:30 -0400, Arye > said:
>
>> It's true that that 185 and 195 indicate the tread width. However, the
>> 60 indicates the ratio of diameter to width, so it goes up
>> proportionally.

>
> Strictly speaking you are correct of course.
> However, 60% of 185 versus 60% of 195?
>
> Without going into heavy (for me) math, I will speculate that the
> difference in diameter will come to about 2%. If I'm going 51 and my
> speedometer is showing 50, I can certainly live with that margin of error.
>
> cheers
>


the speedometer would indeed read 2% too slow if going from a 185/60/14
to a 195/60/14. our beloved miata.net website has a handy little
calculator for this: http://www.miata.net/garage/tirecalc.html



  #19  
Old October 7th 10, 10:07 PM posted to rec.autos.makers.mazda.miata
Lanny Chambers
external usenet poster
 
Posts: 832
Default Tires for a '90 Miata

In article > ,
Christopher Muto > wrote:

> the speedometer would indeed read 2% too slow if going from a 185/60/14
> to a 195/60/14.


Instead of 5% too fast, as it did originally?

> our beloved miata.net website has a handy little
> calculator for this: http://www.miata.net/garage/tirecalc.html


In truth, every Miata speedo seems to be off by a different amount, so
it's a good idea to check it with a stopwatch or GPS. Don't expect the
percentage to be constant over its range, either.

Mine seems fairly close with 205/50-15. More or less. But now the
odometer is off.

--
Lanny Chambers
St. Louis, MO
'94C
 




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