On Tue, 3 Feb 98 23:42:57 EST Sean Bartnik <sbart7kb@www.mwc.edu> writes:
>>
>> BTW, does anyone know of any good reference material on tires? I'm
>quit
>> ignorant in this area, especially on how to interpret the size
>numbers. Maybe
>> a web site?
>>
>Bob,
>I can help with the basics.
>
>Lets start with P185/75R14
>
>The P stands for passenger car rated. Light truck tires are, you
>guessed it LT
>
>The 185 is the tread width in millimeters.
Sorry Sean,
This is the maximum cross section in Millimeters, not tread width.
The variation in tread width on a given size tire can vary as much as
10-15 mm, depending on the manufacturer, as well as within a single
manufacturers various tire styles.
Case in point - I once made the mistake of putting a set of Pirelli
P-44's on my Midget, size 175/70 R 13. The tread was nearly all of 175
mm. it was literally as wide as the sidewall. I not too much later
replaced them with Pirelli P-6's in the same size. (The p-44 was a
terrible handling tire, but that's another story). The P-6 tread was only
about 160-165 mm wide. You could literally see the difference in the
tread width, even without a side-by-side comparison.
For the detail oreinted, the nominal cross section of a tire is only
valid for one specific rim width, that which was used for design
purposes. For each 1/2" difference in rim width, the cross section will
change by about 0.2" (10mm).
Just to keep things confusing.
Rick Morrison
72 MGBGT
74 Midget
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