Know your car's frame

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

Manufacturer Brand

Frame model

Tire Sizing (tire dimensions)

tire types

Service description, (speed ratings, load index)

Maximum tire inflation pressure

Construction type

Uniform Tire Quality Grading (UTQG)

DOT Serial No.

Passenger car tire sizes Passenger Tire Sizes

Most passenger cars are fitted with tires that follow either the P-Metric or Euro-Metric system for tire size.

P-Metric system ( passenger cars)

In this system, the tire width is written in millimeters. To convert millimeters to inches, divide by 25.4. The aspect ratio (the height of the tire section divided by the width of the tire section) provides additional information on top of the tire's size dimensions.

Aspect ratios are given as percentages (75%, 70%, 60%, ...) and are usually referred to as tire series (75, 70, 60, ...). Smaller aspect ratios appear as lower height and wider width.

Euro-Metric system

Europe is the origin of this system, hence the name European Metric System. Most European tire manufacturers produce tires that follow this system. This system is similar to the P-metric system, except for the load-carrying capacity.

A table showing the difference between the P-Metric system and the European Metric system in terms of load capacity for the same frame size and at specific pressures.

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

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

Explanation of the frame symbols:

Tire size, rim (wheel), load capacity, and speed Tire size, Load and Speed Ratings

P-Metric system ( passenger cars):

P215/65R15 80H
P	Additional letter (optional) to indicate the type of vehicle		Intended use or vehicle class for the tire
215	Frame section width in millimeters		Section Width in Millimeters
65	aspect ratio		Aspect Ratio
R	Diametrical structure of the frame fabric layers threads		Radial Construction
15	Wheel 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 indicate the type of vehicle the frame is intended to fit:

P: Passenger car
LT: Light Truck
ST: Special Trailer
T: Temporary (for small-sized spare tires to save space) Space-Saver spare wheel

The use of the letter means the frame conforms to US specifications. TRA , and the absence of the letter means that the frame conforms to European specifications. ETRTO .

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

* / symbol separates two quantities.

* 65 is a two- or three-digit number representing the aspect ratio, which is the ratio of the tire's sidewall height to its width, expressed as a percentage without a % sign. If this information is omitted, it means 82% (82). A number greater than 200 indicates the tire's diameter in millimeters (Japanese specifications).

- :R is an optional character that indicates the composition of the frame's texture layers.

B: Bias (inclined belt)

- D: Diagonal

- R:Radial Qatari

If this letter is absent, it means it has cross-layers. Cross ply

14: A two-digit number indicating the wheel diameter in inches. In a few cases, the diameter is given in metric units. 390 means the wheel diameter is 390 mm.
80: A numerical code (a two- or three-digit number) that denotes the load index. A load index table is used to determine the maximum load the frame can withstand based on that code.
H: A symbol containing a single number or a number and a letter, indicating a speed rating.
Additional symbols:

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

- M+S or M&S: Mud and Snow. This tire has above-average traction in mud, light snow, and low temperatures. However, it is not a winter tire unless it displays a snow mountain or snow symbol. Studded tires 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 in accordance with the regulations of the European Economic Commission
Economic Commission for Europe (ECE) and the number indicates the approving 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, batch number, and production date (two digits indicating the week number plus two digits indicating the year, or two digits indicating the week number and one digit indicating the year of manufacture for tires manufactured before 2000).

- TL: Tubeless (without internal rubber tube)

- TT: A frame that should be used with a tube

Made in: Country of origin

- C: Commercial for small trucks (example 185 R14 C)

- B: A layered fabric frame made from an angled belt for motorcycles (example 150/70 B 17 69 H)

- SFI or Inner: The side facing inwards, for frames that have one mounting direction

- SFO or Outer: The outermost surface, for frames that have one mounting direction.

- TWI: Tread Wear Indicator, Tread Wear Statement.

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

- XL: A frame for cars with a high standard weight eXtra Load

RF: Reinforced tires

Arrows: Directional arrows. Some tire treads are designed to perform best when rotating in a specific direction (clockwise or counterclockwise). These tires have arrows to indicate the direction of rotation. Clockwise tires should not be placed on the left side of the vehicle, and counterclockwise tires on the right side.

- M0: Original tires for the car (Mercedes-Benz)

- N*: Original tire for the car (Porsche)

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

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

Tire load scale table Load Index

The symbol	Pregnancy (kg)	The symbol	Load (kg)	The symbol	Pregnancy (kg)	The symbol	Pregnancy (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 rating is a numerical code to indicate the maximum load (mass or weight) that the tire can carry.

Within the load range “B” according to the European specifications of the Technical Organization for Tires and Wheels
ETRTO European Tire and Rim Technical Organization
This is the load for the frame at a pressure of 36 psi.

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

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

Speed Rating Table :

The symbol	Speed (km/h)	The symbol	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 indicates the maximum permissible speed the tire can withstand for 10 minutes without damage.

* Before 1991, the speed rating was written within the tire size codes, before the "R" tread pattern symbol. 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 speed symbols.

* Tires with a speed rating greater than (300 km/h) often have the speed code written inside brackets as (86Y).

Small truck tires Light truck tires :

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

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

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

- x symbol: symbol used to separate symbols

A 3- or 4-digit number indicates the tire width in inches. If the tire diameter is not given, a tire width number ending in zero (e.g., 7.00 or 10.50) indicates a 92% aspect ratio, while a tire width number not ending in zero (e.g., 7.05 or 10.55) indicates an 82% aspect ratio.

A letter indicating the frame's texture composition (B, D, R):

- B-bias belt

- D- diagonal

- R- Qatari Radial

Two-digit number: Rim diameter in inches

The symbol LT indicates that the frame is suitable for use in light trucks.

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

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

- A number consisting of one or two digits and attached to it an estimated speed (see table)

Load range

The load index for light truck tires indicates the number of plies in the tire's inner fabric and the load pressure (lb/ ^in² ). Tire pressure is also measured in kilopascals (kPa) or bar. 1 psi ( ¹ psi) equals 6.895 kPa. 100 kPa equals 1 bar.

Load amount chart

Load amount Load Range	Number of fabric layers Ply Rating	Pregnancy pressure (lb/ ^in² ) Load Pressure (PSI)
B	4	35
C	6	50
D	8	65
E	10	80
F	12	95

Tire width:

Tires classified as “P-metric” or “P-rated” have their width measured in millimeters. In this classification, the relationship between tire width and rim width is different from that of American letter codes.

Recommended frame width chart for rim width

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

Write the frame diameter instead of writing the frame height:

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

- Example of a 195/55R16 tire:

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

Therefore, the corresponding tire size code is 195/620R16

To differentiate between the two systems and whether the number after the symbol “/” is the aspect ratio or the wheel diameter in mm, the aspect ratio is always less than 100% and therefore less than the number 200 (most car tires have a diameter greater than 200 mm). Therefore, if the number after “/” is greater than 200, then this number indicates the tire diameter, and if the number is less than 200, then this number indicates the aspect ratio and follows the European and American system.

Examples of car tires:

- Car tires for BMW Mini Cooper,
It will be labeled: P195/55R16 85H

P = This frame is for passenger cars; the symbol 'P' stands for the American P system.
195 = Standard width approximately 195 mm at its widest point
/ = Separation mark
55 = Dimensional ratio (Frame wall height is 55% of width - 195 x 0.55)
R = Frame fabric composition type (R=Radial = Diagonal)
16 = Rim diameter in inches
85 = Frame load capacity (515 kg)
H = Speed rate (210 km/h)

- Hummer H1 car tires marked 37X12.5R17LT

37 = Frame diameter in inches
X = Separation symbol
12.5 = Frame width 12.5 inches
R = Frame construction type (R=Radial=Diagonal)
17 = Rim diameter in inches
LT = This is a light truck tire (LT = Light Truck = Light Truck)

Tractor tires:

The numerical designation on tractor tires since 1955 must consist of two or three digits: WD or H/WD, where 'W' is the tire width in inches, 'D' is the rim diameter in inches, and 'H' is the aspect ratio (a percentage of the height to the width without the % sign).

Example 5.00-15
It means a frame that fits on a 15-inch diameter rim, and has a width of 5 inches.

Example 25/5-16
This means a frame that fits on a 16-inch diameter rim, a 5-inch wide rim, and its height is 25% of the width.

Frame specifications:

Uniform Tire Quality Grading (UTQG):

Quality assessments are designed to facilitate the consumer's tire purchasing decision. Their purpose is to provide easily understandable comparative information. However, these assessments are based on test results obtained under specific conditions. Failure to understand the results when compared to the driver's driving style, driving conditions, etc., could lead to this possibility. Therefore, consumers should consult tire specialists.

Quality assessment links tire performance equations to government-defined tests and is determined by tire manufacturers. Tire companies are asked to evaluate tires against three factors:

1- Treadwear
2- Traction
3- Temperature

Tire Manufacture Date:

Tires prior to the year 2000 (three digits), the first two digits indicate the week number of production and the last digit indicates the year number after 1990.
(16 = Week 16 of the year, 4 = 1994)

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