Tire code

Automotive tires are described by several alphanumeric tire codes or tyre codes, which are generally molded into the sidewall of the tire. These codes specify the dimensions of the tire and its key limitations, such as load-bearing ability and maximum speed. Sometimes the inner sidewall contains information not included on the outer sidewall, and vice versa.
The code has grown in complexity over the years, as is evident from the mix of SI and USC units, and ad-hoc extensions to lettering and numbering schemes.
Most passenger car tires sizes are given using either the P Metric tire sizing system or the Metric tire sizing system. Pickup trucks and SUVs use the Light Truck Numeric or Light Truck High Flotation system. Heavy trucks and commercial vehicles use another system altogether.

ETRTO, TRA, and JATMA

The European Tyre and Rim Technical Organisation and the Tire and Rim Association, formerly known as The Tire and Rim Association of America, Inc., are two organizations that influence national tire standards. There exists also the Japan Automobile Tyre Manufacturers' Association, Inc.. In practice, the standards of the three organizations have evolved together and are fairly interchangeable, though the load and inflation tables will give slightly different values for the same size tire.
In the United States, the Office of Vehicle Safety Compliance, a component of the Department of Transportation, is one of the agencies tasked to enforce the Federal Motor Vehicle Safety Standard. Canada has published tire regulations, such as the Motor Vehicle Tire Safety Regulations SOR 95-148.

Metric tire codes

The metric tire code consists of a string of letters and numbers describing the dimensions of the tire, as follows:

Vehicle class

An optional letter indicating the intended use or vehicle class for the tire:

P: Passenger Car
LT: Light Truck
C: Commercial trucks
ST: Special Trailer
M/C: Motorcycle
T: Temporary
A preceding "P" indicates that the tire loads are designed to TRA standards, while the absence of a letter indicates that the tire conforms to ETRTO standards.
Section width

A 3-digit number indicating the "nominal section width" of the tire in millimeters; the widest point from both outer edges. The tire surface that touches the road usually has a narrower width.

Slash

A slash "/" character for character separation.

Aspect ratio

A 2- or 3-digit number indicating the "aspect ratio" of the sidewall height as a percentage of the nominal section width of the tire. If the information is omitted, it is assumed to be 82%. However, if the number is larger than 200, then this is the diameter of the entire tire in millimeters.

Construction

An optional letter or two indicating construction of the fabric carcass of the tire:

B: bias belt
D: diagonal
R: radial
if omitted, it is a cross-ply tire
The R in a radial tire may be preceded by an optional letter indicating the speed rating of the tire according to a deprecated naming system. This letter can be ignored as the actual speed rating is given by the letter appearing at the end of the metric tire code, following the [|load index].
Diameter

A 1- or 2-digit number indicating the diameter, in inches, of the rim that the tires are designed to fit. There is the rare exception of metric-diameter tires, such as the use of the 390 size, which in this case would indicate a rim of 390 mm in diameter. Few tires are made to this size currently. The number may be longer where a half-inch size is used, for example many heavy transport trucks now use 22.5-inch tires.

Load index and load range

The tyre load index on a passenger-car tire is a two- or three-digit numerical code used to cross-reference a load and inflation table that will give the maximum load each tire can carry at a given pressure.
The load index is sometimes used in conjunction with the load range, which appears elsewhere on the tire. It usually consists of two letters. However, it may also be written out as "EXTRA LOAD." It may also be absent entirely, which indicates a Standard Load tire.
These two codes allow one to look up the required cold inflation pressure to carry a given load, according to the load inflation charts or tables. The load tables are too large to include in this article, but may be found at tirepressure.org. Generally, tire codes with a preceding "P" shall reference the P Metric Tire Load Inflation Chart, while those without shall reference the Metric Tire Load Inflation Chart.

Load index	kg	lbs	Load index	kg	lbs	Load index	kg	lbs
0	45	99	100	800	1764	200	14000	30900
1	46.5	102	101	825	1819	201	14500	32000
2	47.5	105	102	850	1874	202	15000	33100
3	48.7	107	103	875	1929	203	15500	34200
4	50	110	104	900	1984	204	16000	35300
5	51.5	114	105	925	2039	205	16500	36400
6	53	117	106	950	2094	206	17000	37500
7	54.5	120	107	975	2149	207	17500	38600
8	56	123	108	1000	2205	208	18000	39700
9	58	128	109	1030	2271	209	18500	40800
10	60	132	110	1060	2337	210	19000	41900
11	61.5	136	111	1090	2403	211	19500	43000
12	63	139	112	1120	2469	212	20000	44100
13	65	143	113	1150	2535	213	20600	45400
14	67	148	114	1180	2601	214	21200	46700
15	69	152	115	1215	2679	215	21800	48100
16	71	157	116	1250	2756	216	22400	49400
17	73	161	117	1285	2833	217	23000	50700
18	75	165	118	1320	2910	218	23600	52000
19	77.5	171	119	1360	2998	219	24300	53600
20	80	176	120	1400	3086	220	25000	55100
21	82.5	182	121	1450	3197	221	25750	56800
22	85	187	122	1500	3307	222	26500	58400
23	87.5	193	123	1550	3417	223	27250	60100
24	90	198	124	1600	3527	224	28000	61700
Load index	kg	lbs	Load index	kg	lbs	Load index	kg	lbs
25	92.5	204	125	1650	3638	225	29000	63900
26	95	209	126	1700	3748	226	30000	66100
27	97.5	215	127	1750	3858	227	30750	67800
28	100	220	128	1800	3968	228	31500	69400
29	103	227	129	1850	4079	229	32500	71700
30	106	234	130	1900	4189	230	33500	73900
31	109	240	131	1950	4289	231	34500	76100
32	112	247	132	2000	4409	232	35500	78264
33	115	254	133	2060	4541	233	36500	80469
34	118	260	134	2120	4674	234	37500	82673
35	121	267	135	2180	4806	235	38750	85429
36	125	276	136	2240	4938	236	40000	88185
37	128	282	137	2300	5071	237	41250	90941
38	132	291	138	2360	5203	238	42500	93696
39	136	300	139	2430	5357	239	43750	96452
40	140	309	140	2500	5512	240	45000	99208
41	145	320	141	2575	5677	241	46250	101964
42	150	331	142	2650	5842	242	47500	104719
43	155	342	143	2725	6008	243	48750	107475
44	160	353	144	2800	6173	244	50000	110231
45	165	364	145	2900	6393	245	51500	113538
46	170	375	146	3000	6614	246	53000	116845
47	175	386	147	3075	6779	247	54500	120152
48	180	397	148	3150	6844	248	56000	123459
49	185	408	149	3250	7165	249	58000	127868
Load index	kg	lbs	Load index	kg	lbs	Load index	kg	lbs
50	190	419	150	3350	7390	250	60000	132300
51	195	430	151	3450	7610	251	61500	135580
52	200	441	152	3550	7830	252	63000	138890
53	206	454	153	3650	8050	253	65000	143300
54	212	467	154	3750	8270	254	67000	147710
55	218	481	155	3875	8540	255	69000	152120
56	224	494	156	4000	8820	256	71000	156530
57	230	507	157	4125	9090	257	73000	160930
58	236	520	158	4250	9370	258	75000	165340
59	243	536	159	4375	9650	259	77500	170660
60	250	551	160	4500	9920	260	80000	176400
61	257	567	161	4625	10200	261	82500	181880
62	265	584	162	4750	10500	262	85000	187390
63	272	600	163	4875	10700	263	87500	192900
64	280	617	164	5000	11000	264	90000	198450
65	290	639	165	5150	11400	265	92500	203920
66	300	639	166	5300	11700	266	95000	209440
67	307	677	167	5450	12000	267	97500	214950
68	315	694	168	5600	12300	268	100000	220500
69	325	716	169	5800	12800	269	103000	227370
70	335	739	170	6000	13200	270	106000	233730
71	345	761	171	6150	13600	271	109000	240345
72	355	783	172	6300	13900	272	112000	246960
73	365	805	173	6500	14300	273	115000	253575
74	375	827	174	6700	14800	274	118000	260190
Load index	kg	lbs	Load index	kg	lbs	Load index	kg	lbs
75	387	852	175	6900	15200	275	121000	266805
76	400	882	176	7100	15700	276	125000	275625
77	412	908	177	7300	16100	277	128500	283343
78	425	937	178	7500	16500	278	132000	291060
79	437	963	179	7750	17100	279	136000	299880
80	450	992	180	8000	17600
81	462	1019	181	8250	18200
82	475	1047	182	8500	18700
83	487	1074	183	8756	19300
84	500	1102	184	9000	19800
85	515	1135	185	9250	20400
86	530	1168	186	9500	20900
87	545	1201	187	9750	21500
88	560	1235	188	10000	22000
89	580	1279	189	10300	22700
90	600	1323	190	10600	23400
91	615	1356	191	10900	24000
92	630	1389	192	11200	24700
93	650	1433	193	11500	25400
94	670	1477	194	11800	26000
95	690	1521	195	12150	26800
96	710	1565	196	12500	27600
97	730	1609	197	12850	28300
98	750	1653	198	13200	29100
99	775	1709	199	13600	30000