December 21, 2016 Mohammad Bata

Know your car's tire

Know your car's tire

We usually see many symbols on car tires, and each one of them has its own interpretation and specific meaning. This information is very important, especially when replacing old tires with new ones, or when measuring the air in the tire. The most important information on the car tire is:

Manufacturer Brand

Frame Model

Tire Sizing (tire dimensions)

Tire type tire types

Service description, (speed ratings, load index)

Maximum inflation pressure

Construction type

Uniform Tire Quality Grading (UTQG)

DOT Serial No.

Passenger car tire size Passenger Tire Sizes

Most passenger cars have tires that follow either the P-Metric or Euro-Metric tire size systems.

P- Metric system (passenger cars) P-Metric

In this system, the tire width is written in millimeters. To convert millimeters to inches, divide the number by 25.4. Aspect ratio (the height of the frame section divided by the width of the frame), gives additional information on the frame dimension information for the size.

The aspect ratio is given as a percentage (75%, 70%, 60%, ....) and is usually referred to as tire series (75, 70, 60, ....). A small aspect ratio appears as less height and more width.

Euro-Metric system

Europe is the source of this system, which is why it is called the European metric system. Most European tire manufacturers make tires that follow this system. This system is similar to the metric system, except for the amount of load carrying capacity.

A table showing the difference between the B-metric system and the European metric system in terms of the load indicator for the same tire size and at specific pressures.

the system System	Frame size Size	Pregnancy indicated Load Index	26 psi	29 psi	32 psi	35 psi	36 psi	44 psi
P-Metric	P195/70R14	90	1135lbs (515kg)	1201lbs (545kg)	1257lbs (570kg)	1312lbs (595kg)		1312lbs (595kg)
Euro-Metric	195/70R14	91	1047lbs (475kg)	1135lbs (515kg)	1224lbs (555kg)		1312lbs (595kg)	1356lbs (615kg)
P-Metric	P205/60R15	90	1124lbs (510kg)	1190lbs (540kg)	1246lbs (565kg)	1301lbs (590kg)		1301lbs (590kg)
Euro-Metric	205/60R15	91	1047lbs (475kg)	1135lbs (515kg)	1224lbs (555kg)		1312lbs (595kg)	1356lbs (615kg)

The previous example also shows that there is another difference between the two systems in terms of maximum tire pressure. The B-metric system has a maximum pressure of 35 psi. As for the European metric system, it is 36 psi.

Explanation of frame codes:

Tire size, rim, load amount and speed Tire size, Load and Speed Ratings

P- Metric system (passenger cars) P-Metric:

P215/65R15 80H
P	An additional character (optional) to indicate the type of vehicle		Intended use or vehicle class for the tire
215	Frame cross-section width in millimeters		Section Width in Millimeters
65	Aspect ratio		Aspect Ratio
R	Diagonal composition of the threads of the layers of the frame fabric		Radial Construction
15	Rim diameter in inches		Rim Diameter in Inches
80	(operating statement)	Pregnancy rate	Load Rating (Index)	(Service Description)
H		swift code	Speed Index (Symbol)

P215/65R15 80H

P*:
An additional letter or letters indicating the type of vehicle in which the tire is supposed to be installed:

P: Passenger car
LT: Light Truck
ST: Special Trailer
T: Space-Saver spare wheel

The use of the letter means that the tire follows US specifications TRA , and the absence of the letter means that the tire follows European specifications ETRTO .

* 215 is a 3-digit number that indicates the width of the tire in millimeters. 215 mm is the widest distance between the two side surfaces of the tire.

*/ A symbol separating two quantities.

* 65 2- or 3-digit number “aspect ratio” The ratio of the height of the tire sidewall to the width of the tire, as a percentage, without the % sign. If this information is not mentioned, this means 82% (82). If the number exceeds 200, this means that this number indicates the diameter of the tire in millimeters (Japanese specifications).

-R: An optional letter indicating the composition of the tire's fabric layers.

- B: Bias oblique belt

- D: Diagonal italic

- R:Radial diagonal

If this letter is not present, it means that it is cross-layered Crossplay

14: A two-digit number indicating the diameter of the rim on which the tire is installed, in inches. There are a few cases where the diameter is mentioned in the metric system. 390 means that the rim diameter is 390 mm.
80: A numerical symbol (a two- or three-digit number), symbolizing the amount (scale) of the load Load index. The load scale table is used to indicate the maximum load that the frame can bear based on that numerical symbol.
H: A symbol that contains a single number or contains a number and a letter, indicating the speed rating.
Additional codes:

There are many signs and symbols which may contain the following:

- M+S or M&S: Mud and Snow. This tire has above average adhesion in mud, light snow, and low air temperatures. But they are not winter tires unless they have a snow mountain or snow symbol on them. Tires equipped with studs have an additional letter “E” (M+SE).

BSW: Black SideWall

- WSW: White SideWall

- OWL: Outlined White Letters (Outer White Lettering)

- E4: Adoption (approval) of the framework according to European Economic Commission regulations
Economic Commission for Europe (ECE) The number indicates the corresponding country.

- 030908: Frame approval number

DOT Code: All tires in the United States must have a code required by the Department of Transportation (DOT). The code identifies the company, manufacturer, model, lot number, and production date (two numbers to indicate the week number plus two numbers to indicate the year number, or two numbers to indicate the week number and a number to indicate the year of manufacture of the tire for tires manufactured before the year 2000).

- TL: Tubeless

- TT: A tire that must be used with a tube

- Made in: Country of manufacture

- C: Commercial for small trucks (ex. 185 R14 C)

- B: Motorcycle slant belt webbed tire (example 150/70 B 17 69 H)

- SFI or Inner: the surface opposite the inside, for tires that have one direction of installation

- SFO or Outer: The surface opposite the outside, for tires that have one direction of installation.

- TWI: Tread Wear Indicator, Tread Wear Indicator.

- SL: Standard load, for normal use and normal load.

- XL: A tire for cars that have a standard eXtra Load weight

- RF: Reinforced tires

- Arrows: Direction arrows. Some tire treads are designed to work best when rotating in a certain direction (clockwise or counterclockwise). These tires have arrows on them to indicate the direction of rotation. Tires that rotate clockwise should not be placed on the left side of the car, or tires that rotate counterclockwise should not be placed on the right side of the car.

- M0: The original tire of the car (Mercedes-Benz).

- N*: Original car tire (Porsche)

- “Star”: the original tire of the car (BMW)

* To facilitate the balancing process, most high-performance tires place a red dot (evenness) and a yellow dot (weight) on the sidewall of the tire to ensure the best balance of the tire and rim combination together.

Frame load scale table :Load Index

code	Load (kg)	code	Load (kg)	code	Load(kg)	code	Load(kg)
Code	Load (kg)	Code	Load (kg)	Code	Load (kg)	Code	Load(kg)
60	250	80	450	100	800	120	1,400
61	257	81	462	101	825	121	1,450
62	265	82	475	102	850	122	1,500
63	272	83	487	103	875	123	1,550
64	280	84	500	104	900	124	1,600
65	290	85	515	105	925	125	1,650
66	300	86	530	106	950
67	307	87	545	107	975
68	315	88	560	108	1,000
69	325	89	580	109	1,030
70	335	90	600	110	1,060
71	345	91	615	111	1,090
72	355	92	630	112	1,120
73	365	93	650	113	1,150
74	375	94	670	114	1,180
75	387	95	690	115	1,215
76	400	96	710	116	1,250
77	412	97	730	117	1,285
78	425	98	750	118	1,320
79	437	99	775	119	1,360

* The tire load gauge is a numerical symbol to indicate the maximum load (mass or weight) that the tire can carry.

In the load range “B” according to the European specifications of the Tire and Wheel Technical Organization
ETRTO European Tire and Rim Technical Organization
This load is for the tire at a pressure of 36 PSI.

According to the TRA Tire and Rim Association of the United States, this tire load is at an inflation pressure of 35 PSI.

*There are slight differences between the two standard specifications for different tire inflation pressures.

Speed Rating table :

code	Speed (km/h)	code	Speed (km/h)
A1	5	L	120
A2	10	M	130
A3	15	N	140
A4	20	P	150
A5	25	Q	160
A6	30	R	170
A7	35	S	180
A8	40	T	190
B	50	U	200
C	60	H	210
D	65	V	240
E	70	Z	over 240
F	80	W	270
G	90	(W)	over 270
J	100	Y	300
K	110	(Y)	over 300

* The code consists of a letter, two letters, or a letter and a number. This gives the maximum permissible speed that the tire can withstand for 10 minutes without endangering it.

* Before 1991, the speed rating was written inside the tire size codes, before the tread code “R”. For example SR (radial - 180 km/h), HR, VR, ZR. The ZR symbol is still used and is often associated with the W and Y symbol for speed.

* Tires with a speed rating greater than (300 km/h), the speed symbol is often written inside brackets as follows (86Y).

Small truck tires Light truck tires :

Some truck tires follow the metric system, which begins with the letters LT instead of beginning with the dimensional specifications.

The tire diameter is not given in the metric system, but in the other system it is written as follows:

- A two-digit number: indicates the diameter of the tire in inches.

- x symbol: a symbol to separate symbols

A 3- or 4-digit number: indicates the width of the tire in inches. If the diameter of the tire is not given, the number indicating the width of the tire ending with a zero (for example, 7.00 or 10.50) indicates that the aspect ratio is 92%, while the number indicating the width of the tire does not end with a zero (for example, 7.05 or 10.55). This indicates that the aspect ratio is 82%.

A letter indicating the tire fabric composition (B, D, R):

- B-bias belt

-D-axial diagonal

- R- Radial

Two-digit number: rim diameter in inches

Symbol LT: indicates that the tire is used for light truck shipments

Some tires have a load indicator and speed rating, as they are not required for this type of tire, but some tire manufacturers place them on the side of the tire:

- A number of one or two digits: indicates the pregnancy indicator (see the following table).

- A one- or two-digit number with a speed rating attached to it (see the table)

Load range

The load gauge for light truck tires indicates the number of layers of the tire's inner fabric and the load pressure (pounds/ ^inch2 ). Tire pressure is also measured in kilopascals or bar. 1 psi ( ² psi) equals 6.895 kilopascals. 100 kilopascals equals 1 bar.

Load amount table

Amount of load Load Range	The amount of fabric layers Play rating	Load pressure(lbs/ ⁱⁿ² ) Load Pressure(PSI)
B	4	35
C	6	50
D	8	65
E	10	80
F	12	95

Tire width:

“P-metric” or “P-rated” tires have a width measured in millimeters. In this classification, the relationship between tire width and rims is different, not like the American letter codes.

Recommended tire width table for rim width

Frame width	Rim width	Frame width	Rim width
P185	5 inch	P255	7 inch
P195	5.5 inches	P265	7 inch
P205	5.5 inches	P275	8 inch
P215	6 inch	P285	8 inch
P225	6 inch	P295	8 inch
P235	6.5 inches	P305	8 inch
P245	7 inch

Writing the tire diameter instead of writing the tire height:

This method is less used in America and Europe (mostly in Japan).

- Example tire 195/55R16:

The diameter of the rim will be 16 x 25.4 = 406 mm, plus twice the height of the tire (the width of the tire in the aspect ratio (height/width) and the height of the tire = 195 x 0.55 = 107 mm)
Thus, tire diameter = rim diameter + 2 tire height = 406 + 2 x 107 = 620 mm.

Thus, the dimension code for a similar tire is as follows: 195/620R16

To differentiate between the two systems, is the number after the symbol “/” the dimensional ratio or the wheel diameter in mm? The dimensional ratio is always less than 100% and therefore less than the number 200 (often all car tires have a diameter larger than 200 mm). Therefore, if the number is present After “/” is greater than 200, this means that this number indicates the diameter of the tire, and if the number is less than 200, then this means that the number indicates the dimension ratio and follows the European and American system.

Examples of car tires:

- BMW Mini Cooper car tires,
It says: P195/55R16 85H

P = This tire is for passenger cars, the symbol 'P' stands for the American P system
195 = Standard width is approximately 195mm at the widest place
/= Separation mark
55 = Aspect ratio (the height of the tire wall is 55% of the width - 195 x 0.55)
R = Tire texture type (R=Radial)
16 = rim diameter in inches
85 = tire load gauge (515 kg)
H = average speed (210 km/h)

The tires of the Hummer H1 are labeled 37X12.5R17LT

37 = tire diameter in inches
X = separation symbol
12.5 = tire width 12.5 inches
R = tire combination type (R=Radial=Radial)
17 = rim diameter in inches
LT = This is a light truck tire (LT=Light Truck=Light Truck)

Tractor tires:

The numerical code written on tractor tires since 1955 requires that it consist of two or three numbers. WD or H/WD where 'W' width is the width of the tire in inches, 'D' diameter is the diameter of the rim in inches, 'H' is the aspect ratio (the percentage of height over width without the % sign).

Example 5.00-15
It means a tire that is mounted on a rim with a diameter of 15 inches and a width of 5 inches.

Example 5/25-16
This means that a tire is installed on a rim with a diameter of 16 inches, a rim with a width of 5 inches, and its height is 25% of the width.

Frame specifications:

Uniform Tire Quality Grading (UTQG):

The quality rating is designed to make the tire purchasing decision easier for the consumer. Their purpose is to provide easy-to-understand comparative information. However, the evaluation is based on the results of tests obtained under special conditions. The lack of understanding of the results when compared to the driver’s circumstances in terms of driving style, driving conditions, etc. may lead to this possibility. That is why the consumer must seek the help of specialists in the field of tires.

Quality ratings link tire performance equations to specific government tests, and are determined by tire manufacturers. Tire companies were asked to evaluate tires on three factors:

1- Treadwear
2- Traction
3- Temperature

Tire Manufacture Date:

Tires before the year 2000 (three numbers), the first two numbers indicate the number of the week of production and the last number indicates the year number after the year 1990.
(16 = week 16 of the year, 4 = 1994)

Tires after the year 2000 (four numbers), the first two numbers indicate the number of the production week and the other two numbers indicate the year.
(42 = week 42 of the year, 02 = 2002)

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