Tire Numbers and What They Mean - Tyre Codes Explained

We all have been looking at those erratic numbers and symbols on tyres now and then, right, but are we supposed to know what alphanumeric tyre numbers means while buying a tyre? The only answer is yes, we must be able to identify the tyre numbers and what they mean.

 

Tyre code has a great significance since the code on the sidewall determines the feature of the tyre, and a portion of its key restrictions, for example, speed limit, and load-bearing capacity. But most importantly the code is decisive in terms of compatibility with your vehicle; you can’t just buy any tyre, that would be ridiculously futuristic, right?

 

Spoiler alert! We are not living in a futuristic fantasy world, so, In order to make an educated buy we must train our naked eye to understand the code on the tyre, so, to begin with, let us start seeing instead of looking. At first glance, the numbers might look like a Dorabella cipher but do not worry this article is going to transform you into tyre guru.

  

Explanation of tyre codes

Let’s look at a typical example of an ISO Metric tyre code:

 

NAME  P215/65R15 95H M+S MANUFACTURER

 

Here is a sketchy breakdown of the code:

 

Code	Description
P	intended use or vehicle class for the tyre
215	Nominal section width in millimetre
65	Nominal aspect ratio
R	Tyres Internal Construction
15	Rim diameter code
95	Load Index
H	Speed Symbol, indicating max. Speed
M+S	Snow condition

 

 

For better understanding let us break down the code in detail piece by piece

  

Service Type - P

It is an optional letter or letters to indicate the intended vehicle for the tyre & that the tyre is engineered according to Tyre and Rim Association (TRA) standards. If there is no letter(s) than the tyre is engineered according to European Tyre and Rim Technical Organisation (ETRTO) standards.

 

Following are letter(s) corresponding to the respective vehicle:

  

1. LT – Light Truck
2. P – Passenger Car
3. ST – Special Trailer
4. C – Euro-metric sizes
5. M – Motorcycles.
6. T – The tyre is temporary (spare).
7. No letter – A metric-sized tyre

  

Section Width – 215

 

                The measurement, in millimeters,  from inner sidewall to the outer sidewall of the tyre is called Section width of a tyre also known as cross section width.

 

Here is how is the section width is measured

 

1. There is no load on the tyre
2. The tyre is installed on the industry-grade measuring rim
3. The tyre is inflated to a proper pressure

  

The width of the measuring rim is coequal to tyre size. The size of the rim changes with the tyre's Section Width and Aspect Ratio. Following are the rim widths and their corresponding tyre widths.

  

Rim Width	Min tyre width	Ideal tyre width	Max tyre width
5.0"	155 mm	165 to 175 mm	185 mm
5.5 "	165 mm	175 to 185 mm	195 mm
6.0 "	175 mm	185 to 195 mm	205 mm
6.5 "	185 mm	195 to 205 mm	215 mm
7.0 "	195 mm	205 to 215 mm	225 mm
7.5 "	205 mm	215 to 225 mm	235 mm
8.0 "	215 mm	225 to 235 mm	245 mm
8.5 "	225 mm	235 to 245 mm	255 mm
9.0 "	235 mm	245 to 255 mm	265 mm
9.5 "	245 mm	255 to 265 mm	275 mm
10.0"	255 mm	265 to 275 mm	285 mm
10.5"	265 mm	275 to 285 mm	295 mm
11.0"	275 mm	285 to 295 mm	305 mm
11.5"	285 mm	295 to 305 mm	315 mm
12.0"	295 mm	305 to 315 mm	325 mm
12.5"	305 mm	315 to 325 mm	335 mm
*Minimum figures are a safe figure *Stretching tyres not recommended outside this table

  

Nominal Aspect Ratio - 65

 

                Percentage of the nominal section width of the tyre as a sidewall height is known as the aspect ratio. If the nominal aspect ratio is 45 than the sidewall height of the tyre is 45%, hence tyres sidewall height is directly proportional to aspect ratio. In case, the nominal aspect ratio exceeds 200 then this is the indication that the diameter of the entire tyre is in millimeters. If there is no aspect ratio than it is assumed to be 82%.

 

Tyre internal construction - R

  

                The material used in the construction of the fabric carcass of the tyre is indicated with this optional letter. If the letter doesn’t exist this means the tyre is cross-ply.

 

Following are letters specifying the materials used in tyres internal construction.

 

1. B - Bias Belt
2. D - Diagonal
3. R - Radial
4. RF – Run Flat

Rim diameter code - 15

  

                Rim diameter is expressed in inches, it indicates the wheels that the tyres are engineered to fit.

  

Diameter in inches	Width in inches	Measured on this rim width	Metric size tyre	Will fit in these rims
25.5	8.9	7	215/50/17	6 – 7.5
26.3	8.9	7	215/55/17	6 – 7.5
25.9	9.17	7	225/50/17	6 – 8
26.8	9.2	7	225/55/17	6 – 8
26.7	9.17	7	225/55/17	6 – 8
25.4	9.3	8	235/45/17	7.5 – 9
25.7	9.6	8	245/45/17	7.5 – 9
28.6 Stock 18’’ tyres	9	6.5	225/60/18	6 – 8
26.6	9.57	8	245/45/18	7.5 – 9

  

Load index – 95

 

                The maximum load a tyre can carry when inflated to recommended pressure is known as load index. The manufacturer assigns load index to a tyre.

Following are the Load Index (LI) a numerical code associated with the maximum load (Kg) a tyre can carry.

  

LI	kg	LI	kg	LI	kg	LI	kg	LI	kg
50	190	65	290	80	450	95	690	110	1060
51	195	66	300	81	462	96	710	111	1090
52	200	67	307	82	475	97	730	112	1120
53	206	68	315	83	487	98	750	113	1150
54	212	69	325	84	500	99	775	114	1180
55	218	70	335	85	515	100	800	115	1215
56	224	71	345	86	530	101	825	116	1250
57	230	72	355	87	545	102	850	117	1285
58	236	73	365	88	560	103	875	118	1320
59	243	74	375	89	580	104	900	119	1360
60	250	75	387	90	600	105	925	120	1400
61	257	76	400	91	615	106	950	121	1450
62	265	77	412	92	630	107	975	122	1500
63	272	78	425	93	650	108	1000	123	1550
64	280	79	437	94	670	109	1030	124	1600

  

Following are the Load capacities at their respective tyre pressures – standard load car tyres.

  

Load capacity (kg) at tyre pressure (bar)
Load Index	2.0	2.1	2.2	2.3	2.4	2.5
62	220	230	240	250	255	265
63	230	235	245	255	265	272
64	235	245	255	260	270	280
65	245	250	260	270	280	290
66	250	260	270	280	290	300
67	255	265	275	285	295	307
68	265	275	285	295	305	315
69	270	285	295	305	315	325
70	280	290	300	315	325	335
71	290	300	310	325	335	345
72	295	310	320	330	345	355
73	305	315	330	340	355	365
74	315	325	340	350	365	375
75	325	335	350	360	375	387
76	335	350	360	375	385	400
77	345	360	370	385	400	412
78	355	370	385	400	410	425
79	365	380	395	410	425	437
80	375	390	405	420	435	450
81	385	400	415	430	445	462
82	395	415	430	445	460	475
83	405	425	440	455	470	487
84	420	435	450	470	485	500
85	430	450	465	480	500	515
86	445	460	480	495	515	530
87	455	475	490	510	525	545
88	470	485	505	525	540	560
89	485	505	525	545	560	580

  

Speed Symbol (SSY) – H

 

                Speed symbol determines the maximum speed a tyre can carry a load specified via load index.

 

SPEED SYMBOL	SPEED (KM/H)	SPEED (MPH)
Al	5	3
A2	10	6
A3	15	9
A4	20	12
AS	25	16
A6	30	19
A7	35	22
A8	40	25
13	50	31
C	60	37
0	65	40
E	70	43
F	80	50
G	90	55
J	100	62
K	110	68
L	120	75
M	130	81
N	140	87
O	150	93
P	160	99
Q	170	106
R	180	112
S	190	118
T	200	124
U	210	130
V	240	149
W	270	168
Y	300	186
(Y)ZR*	314 OPEN-ENDED	195 OPEN-ENDED

  

Snow condition – M+S

 

                These letters indicate the weather conditions tyres are fit for. Snow tires have depper tread patterns than those on summer tires, expanding footing on snow and ice.

 

M+S or M&S	Mud and Snow
M+T or  M&T	Mud and Terrain

  

Further into tyre codes

  

                Following are some of the tyre codes revealing additional information associated with the tyre.

BSW	Black Sidewall
BSB	Broken Serrated Band
WSW	White Sidewall
OWL	Outline white lettering
ORWL	Outline raised white lettering
RWL	Raised white lettering
VSB	Vertical serrated band
BSL	Black serrated letters
E4	E: approved according to ECE-Regulations 4: country of approval
030908 (XXXXXX)	Approval number
TL	Tubeless tyre
TT	Tube-type tyre
C	Commercial tyre (Light Truck)
B	Bias Belted Tyre (Motorcycle)
SFI	Side Facing Inwards; inside of asymmetric tyres
SFO	Side Facing Outwards; inside of asymmetric tyres
LL	Light load
SL	Standard load
XL	Extra load