What tire markings mean

When buying a new tire or when we just want to check the parameters and performances of our current vehicle tires, we need to read the tire side markings. The numbers and symbols found on the sidewall of every tire give significant details about their size, performance and manufacturing dates.

The most common and visible marking is the size marking. The symbol for size has the following format:

TireWidth [mm] / AspectRatio [%] Construction RimDiameter [in]

Example: 225/60R18

The tire width (255), in millimeters, is the distance measured from sidewall to sidewall.

The aspect ratio (60), in percentage, is the ratio between the tire height and width.

\[\text{Aspect Ratio [%]}=\frac{\text{Tire Height [mm]}}{\text{Tire Width [mm]}} \cdot 100\]

An aspect ratio of 60 means that the height of the tire is equal to 60% of the tire’s width. The higher the aspect ratio, the higher the height of the tire. Off road tires have high aspect ratio since tire height is good for rocky, bumpy roads. Sports, high performance tires have low aspect ratio, since the lower the height of the tire, the better is the stability of the vehicle and the grip of the wheel.

The construction symbol gives details about the inside layers of the tire (plies), how are they arranged across the tire. The most common type of tires is the Radial tire (R). There are also Diagonal tires (D) or Belted (B).

The wheel/rim diameter, in inches, is the external diameter of the wheel/rim. It is also the internal diameter of the tire.

The are also additional markings after the size marking. These are the load index and the speed index.

TireWidth [mm] / AspectRatio [%] Construction RimDiameter [in] LoadIndex SpeedIndex

Example: 245/40R18 97V

The load index (LI) indicates the maximum weight supported by the tire when properly inflated. For example the load index 97 means that the tire can withstand 730 kg of load (weight).

A comprehensive load index table is below:

LI	kg	LI	kg	LI	kg	LI	kg	LI	kg	LI	kg	LI	kg
0	45	25	92.5	50	190	75	387	100	800	125	1650	150	3350
1	46.2	26	95	51	195	76	400	101	825	126	1700	151	3450
2	47.5	27	97.5	52	200	77	412	102	850	127	1750	152	3550
3	48.7	28	100	53	206	78	425	103	875	128	1800	153	3650
4	50	29	103	54	212	79	437	104	900	129	1850	154	3750
5	51	30	106	55	218	80	450	105	925	130	1900	155	3850
6	53	31	109	56	224	81	462	106	950	131	1950	156	4000
7	54.5	32	112	57	230	82	475	107	975	132	2000	157	4125
8	56	33	115	58	238	83	487	108	1000	133	2060	158	4250
9	58	34	118	59	243	84	500	109	1030	134	2120	159	4375
10	60	35	121	60	250	85	515	110	1060	135	2180	160	4500
11	61.5	36	125	61	257	86	530	111	1090	136	2240	161	4625
12	63	37	128	62	265	87	545	112	1120	137	2300	162	4750
13	65	38	132	63	272	88	560	113	1150	138	2360	163	4875
14	67	39	136	64	280	89	580	114	1180	139	2430	164	5000
15	69	40	140	65	290	90	600	115	1215	140	2500	165	5150
16	71	41	145	66	300	91	615	116	1250	141	2575	166	5300
17	73	42	150	67	307	92	630	117	1285	142	2650	167	5450
18	75	43	155	68	315	93	650	118	1320	143	2725	168	5600
19	77.5	44	160	69	325	94	670	119	1360	144	2800	169	5800
20	80	45	165	70	335	95	690	120	1400	145	2900	170	6000
21	82.5	46	170	71	345	96	710	121	1450	146	3000	171	6150
22	85	47	175	72	355	97	730	122	1500	147	3075	172	6300
23	87.5	48	180	73	365	98	750	123	1550	148	3150	173	6500
24	90	49	185	74	375	99	775	124	1600	149	3250	174	6700

The speed index (SI) or speed rating, indicates the maximum speed which can be withstand by the tire. Usually the speed index of the tire is matching the maximum speed of the vehicle. For example, the speed index V means that the maximum speed capability of the tire is 240 kph.

A comprehensive speed index table is below:

SI	Maximum Speed [kph]	SI	Maximum Speed [kph]
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 manufacturing date of the tire is usually displayed by four digits inside an oval filed. For example 2514 means that the tire was produced in the 25^th week of the year 2014.

A special marking is for winter tires. If the tire has the symbols M+S (Mud and Snow), it’s designed to achieve better values for handling and traction in winter conditions, compared with a summer tire (without M+S marking).

The snow flake symbol also known as 3PMSF (Three Peak Mountain Snow Flake) symbol is is also related to winter tires and it’s required by North American legislation.

Tires can also have traction and temperature grades. The traction grade indicates the wet traction performance of the tire under controlled testing conditions. A tire with an “AA” traction rating has outstanding traction performance in wet conditions. Traction grades can be: AA, A, B or C

Temperature grade indicates the capacity of the tire to withstand high temperature. A tire with a high temperature grade can operate at higher vehicle speeds. The best temperature grade is A, followed by B (medium) and C (low).

Treadwear grades are set based on standardized government tests, which predict the expected treadwear of a tire. For example, a tire with a treadwear grade of 220 should last twice as long as a tire with a treadwear grade of 110.

Introduced by the Economic Commission for Europe (ECE), the tire E mark is now mandatory on all European tires. It also signals that the tire meets certain requirements in terms of sizing, performance and marking. For example E4 enclosed in a circle means that the tire was produced and approved in Netherlands.

A comprehensive E mark table is below:

Code	Country	Code	Country
E1	Germany	E21	Portugal
E2	France	E22	Russian Federation
E3	Italy	E23	Greece
E4	Netherlands	E24	Ireland
E5	Sweden	E25	Croatia
E6	Belgium	E26	Slovenia
E7	Hungary	E27	Slovakia
E8	Czech Republic	E28	Belarus
E9	Spain	E29	Estonia
E10	Yugoslavia	E31	Bosnia and Herzegovina
E11	United Kingdom	E32	Latvia
E12	Austria	E34	Bulgaria
E13	Luxembourg	E37	Turkey
E14	Switzerland	E40	Macedonia
E16	Norway	E43	Japan
E17	Finland	E45	Australia
E18	Denmark	E46	Ukraine
E19	Romania	E47	South Africa
E20	Poland	E48	New Zealand

Starting with November 2012 all new tires sold in the European Union (EU) must be provided with a standardized tire label. The information on the label is related to three tire properties:

• rolling resistance
• grip in wet conditions
• road noise

The labels are divided in three categories: C1 (passenger vehicles), C2 (light utility vehicles) and C (heavy commercial vehicles). Best grade is A, worst is G.

The maximum permissible inflation pressure (e.g. 45 psi = 3.1 bar) is the maximum air pressure at which the tire can be inflated. This pressure should be much higher than the nominal working pressure of the tire (e.g. 2.1 bar).

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