Definition: On the sidewall of every tire is information about tire size, maximum load rating, maximum inflation pressure, tire construction and performance standards. Tread wear is a comparative rating of how long the tire will last compared to other tires. The higher the number, the longer the predicted life of the tread. A tire with a 200 rating should go twice as many miles as one with a 100 rating.

The numbers do not correspond to a fixed mileage figure because there are so many variables that affect the life of the tread (maintaining the correct inflation pressure is one of the most important). The traction rating is a measure of the tires ability to stop on wet pavement. An "A" is the best rating, "B" is average, and "C" is the lowest acceptable rating. The temperature rating is an indication of how cool the tire runs as highway speeds. Again, an "A" is the best while "C" is the lowest acceptable rating. Performance tires also carry a speed rating: "H" rated tires are good for speeds up to 130 mph, and "V" rated tires are certified for speeds above 130 mph.

Old System:
205/60VR15

205 = Section width in millimeters
60 = Aspect ratio
V = Speed rating (unlimited V)
R = Radial construction
15 = Rim diameter in inches
V = Speed symbol (limited V)*


New System:
205/60R1591V

205 = Section width in millimeters
60 = Aspect ratio
R = Radial construction
15 = Rim diameter in inches
91 = Load index*


Note: Always consult the manufacturer for the maximum speed of Unlimited V and Z tires. Speed rating is identified as a part of the tire's sizing or service description (see above).

* In the latest attempt to standardize tire designations, all ratings except unlimited VR and ZR incorporate the speed symbol and load index as the tire's service description.

"ZR" Rated Tires

When "ZR" appears in the size designation with the service description, the maximum speed is as indicated by the service description.


Tire Designation Maximum Speed

P275/40ZR17 93W 270 km/h (168 mph)

P275/40ZR17 93Y 300 km/h (186 mph)


For tires having a maximum speed capability above 240 km/h (149 mph), a "ZR" may appear in the size designation. For tires having a maximum speed capability above 300 km/h (186 mph), a "ZR" must appear in the size designation. Consult tire manufacturer for maximum speed when there is no service description.



Speed Symbols

Speed Symbol-----Speed (km/h)----Speed (mph)

A---------------15--------------3

A2--------------10--------------6

A3--------------15--------------9

A4--------------20--------------12

A5--------------25--------------16

A6--------------30--------------19

A7--------------35--------------22

A8--------------40--------------25

B---------------50--------------31

C---------------60--------------37

D---------------65--------------40

E---------------70--------------43

F---------------80--------------50

G---------------90--------------56

J---------------100-------------62

K---------------110-------------68

L---------------120-------------75

M---------------130-------------81

N---------------140-------------87

P---------------150-------------94

Q---------------160-------------100

R---------------170-------------106

S---------------180-------------112

T---------------190-------------118

U---------------200-------------124

H---------------210-------------130

V*--------above 210-------above 130

V---------------240-------------149

W---------------270-------------168

Y---------------300-------------186

* For Unlimited V tires without the Service Description, the speed category is over 210 km/h (130 mph).



Also look here for any other info that you may need. Click Here (http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=35)

Wanna know how much of a diffrence that new wheel and tire will make as far as the fitment and revs per mile? Then look here. Click Here (http://www.bigcustomwheels.com/info_specs.jsp)

Remember stock P-Type Wheels are (14x7 w/8mm offset)

I have had a few newer forum members ask me allot about tires and yeah when I say allot I mean about 5 or 6 and to be honest to be kept being asked about the same thing does get annoying. So I'm putting this up and I hope a mod may consider putting a sticky on it.

Don't forget the UTQG rating.

The UTQG tire rating system:

The U.S. DOT and NHTSA's UTQG (Uniform Tire Quality Grade) system was put in place to aid consumers in understanding the performance carchteristics and quality of new tires purchased for their vehicle. These ratings are required by LAW to be provided to you on all passenger and light truck tires. Off road tires such as pure racing tires and knobby rock crawling tires are exempt from having these tests, also winter tires are exempt.

The tests are conducted by the tire manufacturers themselves or a third party, the DOT has the right to inspect the test data and charge fines if inconsitencies are found.

UTQG Treadwear ratings:

Treadwear ratings give you an idea of how long the tire will last. The higher the number the longer the tire is expected to last. For instance a tire with a 400 treadwear rating should last twice as long as a tire with a treadwear rating of 200. While the treadwear rating is the most often touted rating of a particular tire it is the most inconsistent of the ratings. A fleet of test vehicles are run on 400 mile loops in West Texas until 7200 miles is reached to determine the life expectancy of a tire. Here is where the inconsistency lies, it is up to the tire manufacturer to determine how long that particular model of tire will last based on the wear data collected from the 7200 mile test. A treadwear rating of 100 would mean that the manufacurer has determined that the tire is completely used up after the 7200 mile test, a rating of 200 would last 14400 an so on. because of these inconsistencies brand "A" with a treadwear rating of 300 will not neccesarily last as long as brand "B" with a treadwear rating of 300.

The UTQG Traction rating:

The UTQG Traction rating is a rating of a tires straight line acceleration charachteristics on a WET surface. This test does not evaluate dry cornering, dry acceleration, or wet cornering. The ratings are AA (the highest) A, B, and C. Below is a chart of g-force ratings for tires on both concrete and asphalt based on the UTQG Traction rating system.

Traction Grades........Asphalt g force..........Concrete g force
AA..............................Above 0.54................0.41
A................................Above 0.47................0.35
B................................Above 0.38................0.26
C............................Less Than 0.38...............0.26

The UTQG Temerature rating:

The UTQG Temperature rating evaluates the ability of a particular tire to dissipate heat, an overheated tire will break apart and can be very dangerous. The 3 UTQG Temperature ratings are A, B, and C below is a chart of maximum speeds based on the UTQG Temperature rating. Every tire sold in the US must be able to meet at least the "C" standard for temperature.

Temperature Grades......Speeds in mph
A...................................Over 115
B...................................Between 100 to 115
C....................................Between 85 to 100

I would like to thank the Tire Rack for the great article that I used to help me write this found here: http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=48&currentpage=17

This tire marking means your dually just ran the F into something.
http://plus.maths.org/issue37/features/budd/skid_marks.jpg

This tire marking means you might have a bit of a brake bias issue.
http://i.cnn.net/cnn/2003/US/South/12/29/seven.dead.ap/vert.road.jpg

This tire marking means it might be winter...
http://www1.istockphoto.com/file_thumbview_approve/133344/2/istockphoto_133344_skidmarks_in_the_snow.jpg

This tire marking means you might want to watch out for the ocean...
http://www1.istockphoto.com/file_thumbview_approve/2734138/2/istockphoto_2734138_skidmarks_on_the_beach.jpg

Hope this helps...

--billyM

:zzzzz: ^ Excellent

Hope this helps...

--billyM



Hahahahaha! Classic!

Good info and a nice write-up. Did you know that a lot of this material is already covered in a previous thread (that is a sticky in the wheels and tires section):

http://forums.celicasupra.com/showthread.php?t=23770

Even some of us noobs can find the existing stickies. :)

Yawn.

Do you need to be tucked in?

Yes plz would you.