How to read tire sizes? (ie. what does P175/70SR13 mean?)
Anthony Olejnik
I`m trying to understand tire sizes.
For example, the recommended tire size for my car (as per the owners
manual) is P175/70SR13. What does this mean?
I know the 13 is the wheel diameter in inches.
What does the P stand for?
What does the 175 stand for?
What does the /70 stand for?
What does the S stand for?
What does the R stand for? (Radial, I assume.)
What actually *IS* a Radial tire?
What are the other types?
Is one type better than another?
Any help would be *GREATLY* appreciated.
Thanks in advance.
--tony
Chris Craddock
|>
|> I`m trying to understand tire sizes.
|> For example, the recommended tire size for my car (as per the owners
|> manual) is P175/70SR13. What does this mean?
|>
|> I know the 13 is the wheel diameter in inches.
|> What does the P stand for?
P=passenger (as in passenger car, not light truck or other)
|> What does the 175 stand for?
Sidewall to sidewall width in milimeters
|> What does the /70 stand for?
Aspect ratio, i.e. % ratio of sidewall height from bead to tread
to tire width (175mm in this case). Your sidewalls are .7x175=122.5mm
|> What does the S stand for?
Its a speed rating. S is good for 180Km/h or 112mph
|> What does the R stand for? (Radial, I assume.)
Yes.
|> What actually *IS* a Radial tire?
A tire where the plies (the strips which make up the internals of the
tire carcass) are arranged radially, like the spokes of a cart wheel
|> What are the other types?
Cross ply was the dominant type until Michelin introduced the first
radials in the 1950s. A cross ply has the plies arranged in opposing
diagonals which look like an X when viewed from the tread.
|> Is one type better than another?
You betcha. Radials are far better than other tires for all passenger
type applications. The radial plies leave the sidewalls softer and able
to deform. The deformation allows the tread contact patch to stay flat
on the road and hence gives more grip.
Cross plies are better for heavy load carrying applications (such as
truck tires, although the jury is still out on that) and also for off
road applications where the risk of sidewall damage is relatively high.
|> Any help would be *GREATLY* appreciated.
|>
|> Thanks in advance.
You're welcome.
|>
|> --tony
Chris
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Scott Thomson
>
>I`m trying to understand tire sizes.
>For example, the recommended tire size for my car (as per the owners
>manual) is P175/70SR13. What does this mean?
Check the latest issue of Consumer Reports (Feb. 92) (I just got mine yesterday).
They have a report on tires and a sidebar describing what the letters/numbers
mean.
>
>I know the 13 is the wheel diameter in inches.
>What does the P stand for?
Passenger car tire.
>What does the 175 stand for?
Width of the tread in millimeters.
>What does the /70 stand for?
Ratio of side wall to tread width. The sidewall height would be be 70% as
much as the width.
>What does the S stand for?
Speed rating. "S" is good for sustained speeds upto 112 MPH.
>What does the R stand for? (Radial, I assume.)
Yes, radial.
Also, the same issue discusses auto theft deterents, including the Club and
Lojack. I have not read that article yet.
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Scott Thomson Post Office Box 869
Neenah, Wisconsin, 54957-0869
s...@thomson.uucp (414) 722-5700
richard welty
>I`m trying to understand tire sizes.
this will be covered in the monthly postings (scheduled to resume
in 7 days), but here are the basics:
>For example, the recommended tire size for my car (as per the owners
>manual) is P175/70SR13. What does this mean?
>I know the 13 is the wheel diameter in inches.
>What does the P stand for?
passenger; the other designation is LT (for light truck.) these
designations are used inconsistently, and the absence of either
designation indicates a tire suitable for passenger car usage.
>What does the 175 stand for?
the section width in mm; this is usually wider than the tread width.
>What does the /70 stand for?
the aspect ratio of the tire; it indicates that the sidewall height
is 70% of the section width of the tire (e.g., 0.70 * 175)
>What does the S stand for?
that is a speed rating; in this case, S indicates that the tire,
when properly inflated and operated at less than its maximum load,
is good for up to 112mph continuous speed in a straight line for
some time period which i've forgotten. T = 118mph, H=130, V= over 130,
and Z= something silly and very high.
note that these ratings do not account for cornering loads; it is
possible to cook a Z rated tire at lime rock, where the top speed
might be 105 or 110 in a street car, due to cornering stress on the
tire.
there is a change in load and speed designations in progress;
you may in the near future see a 175/70R13 80S as an alternative
designation. the S is moved to the end, and paired with a load
index. this index indicates the max load specified at the max
speed, given that the tire is properly inflated. in purchasing
replacement tires, if you know what the minimum load index is for the
car, look for a number which is at least that. if you don't know that
number, then look for a load index which is at least as high as that
on the OE tires.
>What does the R stand for? (Radial, I assume.)
yep.
>What actually *IS* a Radial tire?
it has to do with the internal construction, and the layout of the
belts. there are probably others on the net better qualified to explain
this than i.
>What are the other types?
bias and bias belted
>Is one type better than another?
radials are generally prefered on modern passenger cars, but bias
type tires do have their merits, and are still used in some applications
(mostly competition.)
cheers,
richard
--
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we...@cabot.balltown.cma.com
Kevin M Geraghty
>
> I`m trying to understand tire sizes.
> For example, the recommended tire size for my car (as per the owners
> manual) is P175/70SR13. What does this mean?
>
> I know the 13 is the wheel diameter in inches.
> What does the P stand for?
> What does the 175 stand for?
> What does the /70 stand for?
> What does the S stand for?
> What does the R stand for? (Radial, I assume.)
>
> What actually *IS* a Radial tire?
> What are the other types?
> Is one type better than another?
>
the 70 is the "aspect ratio'", or height of the tire wall as a
percentage of the width.
SR, I THINK, is steel-belted radial?
P, no idea
Andrew Evans
>I`m trying to understand tire sizes.
>For example, the recommended tire size for my car (as per the owners
>manual) is P175/70SR13. What does this mean?
>I know the 13 is the wheel diameter in inches.
>What does the 175 stand for?
The width of the tire in millimeters.
>What does the /70 stand for?
The aspect ratio of the tire: the percentage of sidewall to tread
width as a percentage. The sidewall on this tire would be 122.5 mm
high, which I got by multiplying 175 mm by 70%.
>What does the S stand for?
The speed rating of the tire. S-rated tires are rated up to speeds of
130 MPH. More than that, and the tire may overheat and explode, which
would be bad news at that speed.
richard welty
>In article <63...@netnews.upenn.edu> to...@scotty.dccs.upenn.edu (Anthony Olejnik) writes:
>>For example, the recommended tire size for my car (as per the owners
>>manual) is P175/70SR13. What does this mean?
>>What does the 175 stand for?
>Width of the tread in millimeters.
er, this is a very common misconception. the 175 is _section_ width,
not _tread_ width; it is the width of the tire at its widest point
in cross section, which is generally somewhere on the sidewall. tread
width is almost always narrower than section width; the degree to which
it is narrower varies from tire model to tire model, so i can't give
you any reliable way of figuring it out.
Henry Sevilla
> I know the 13 is the wheel diameter in inches.
> What does the /70 stand for?
> What does the S stand for?
> What does the R stand for? (Radial, I assume.)
>
> What actually *IS* a Radial tire?
> What are the other types?
> Is one type better than another?
>
> Any help would be *GREATLY* appreciated.
>
> Thanks in advance.
>
> --tony
The other, older type of tire that I know of is the bias-ply.. I don't
know much about it, other than it isn't used much today. It's cheaper, but
gives about 5-7% fuel economy LESS than radials, when properly inflated..
The 'P' stands for Passenger car.
175 is the width of the tire in mm's..
/70 is a % of width that is the height of the tire. Thus, the tire is
(70% of 175) high.
The S (someone help me on this), either means it is a Steel-belted, or
it means a safe maximum speed of 112mph (H for 130, and V for over 130mph)
The R means Radial.
Hope this helps.
-Henry
--
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P. J. Remner
> I`m trying to understand tire sizes.
> manual) is P175/70SR13. What does this mean?
> I know the 13 is the wheel diameter in inches.
> What does the 175 stand for?
> What does the /70 stand for?
> What does the S stand for?
> What does the R stand for? (Radial, I assume.)
>
whoops... too much deleted... oh well.... anyway...
175 is the tire width (not tread width) in millimetres.
70 means the height of the sidewall. (70 percent of 175)
S is the speed rating.
Just for the record..
T = 112 mph.
S = 118 mph.
H = 130 mph.
V = 149 mph.
Z = 150+ mph.
R stands for radial. Again, just for the record..
R = Radial
B = Bias-ply
D = Bias-belted
Radial means that the belts, instead of going diagonally across the
tread like bias-ply and bias-belted, go longitudinally, or
around the tire.
--
aj...@cleveland.Freenet.Edu (Peter "Lizard King" Remner)
I bought me an illusion and I put it on the wall
I let it fill my head with dreams and I had to have them all...
richard welty
>The speed rating of the tire. S-rated tires are rated up to speeds of
>130 MPH. More than that, and the tire may overheat and explode, which
>would be bad news at that speed.
these days, the tire is more likely to chunk or blister than rupture,
at least in my experience.