# How To Reading A Tyre Sidewall

P235/65R15 102S
P = Tyre Type (Passenger)
215 = Section width in millimetres
65 = Aspect Ratio
15 = Rim diameter in inches
95 = Load index (see chart)
S =Speed rating ( see Chart)

525/550-17
525/550 = Section width in inches
17 = Rim diameter in inches
4 PLY = Ply Rating
90 = Load index (see chart)
P =Speed rating ( see Chart)

TYRE TYPE
P= Passenger car , LT= Light Truck

Section Width
Is the measurement from sidewall to sidewall, at its widest point.
On Radial Tyres this is always a single measurement
On Vintage X ply tyres this can have multipliable sizes.

ASPECT RATIO/SERIES NUMBER
The height and width relationship of the tyre. This number is determined by dividing a tyres section height by its section width. For example: the section height of 205/70R14 is 70% of the section width which is 205.

RIM DIAMETER
The diameter of the rim at the bead seat. The most accurate method to determine the diameter is to measure the circumference of the rim at the bead seat and divide by 3.14

The load index is an assigned number ranging from 0 to 279 that corresponds with the load carrying capacity of the tyre. Most car passenger car.

Index No Kgs Index No Kgs Index No Kgs Index No Kgs Index No Kgs Index No Kgs
40 140 57 230 74 375 91 615 108 1000 125 11650
41 145 58 236 75 387 92 630 109 1030 126 1700
42 150 59 243 76 400 93 650 110 1060 127 1750
43 155 60 250 77 412 94 670 111 1090 128 1800
44 160 61 257 78 425 95 690 112 1120 129 1850
45 165 62 265 79 437 96 710 113 1150 130 1900
46 170 63 272 80 450 97 730 114 1180 131 1950
47 175 64 280 81 462 98 750 115 1215 132 2000
48 180 65 290 82 475 99 775 116 1250 133 2060
49 185 66 300 83 487 100 800 117 1285 134 2120
50 190 67 307 84 500 101 825 118 1320 135 2180
51 195 68 315 85 515 102 850 119 1360 136 2240
52 200 69 325 86 530 103 875 120 1400 137 2300
53 206 70 335 87 545 104 900 121 1450 138 2360
54 212 71 345 88 560 105 925 122 1500 139 2430
55 218 72 355 89 580 106 950 123 1550 140 2500
56 224 73 365 90 600 107 975 124 1600 141 2575

Speed Rating

For MOT requirements in the UK, it is not necessary to fit a tyre with a speed rating to match the original vehicle fitments or the maximum speed of the vehicle. Tyres must be suitable for the purpose for which the vehicle will be used.Insurance companies might say that a vehicle should be fitted with the tyres having the speed rating recommended by the car manufacturer: but even if you fit Z-rated tyres for speeds over 150 mph they will not insure you if you drive in excess of 70 mph in this country!
The vehicle manufacturer has to recommend a tyre with a rating to match the maximum speed of the car because when it leaves the factory he does not know exactly where the car is going or for what purpose it might be used. You might want to use the car in a country where higher speed limits apply than the UK or take it to a race track at the weekend.
The tyre speed rating (i.e. S) is the maximum speed for which the tyre is rated. For example, the S rating identifies speeds up to 112 mph

Speed Symbol Speeds UP TO Speed Symbol Speeds UP TO
L 75 MPH H 130 MPH
M 81 MPH V 149 MPH
P 93 MPH VR (1) 130 MPH Plus
Q 100 MPH W 168 MPH
R 106 MPH Y 186 MPH
S 112 MPH ZR (2) 149 MPH Plus
T 118 MPH

(1) Tyres marked "VR" within the size designation ( 235/60VR15) are designed for speeds in excess of 130 MPH
(2) Tyres marked "ZR" within the size designation ( 235/60ZR15) are designed for speeds in excess of 149 MPH
Tyres marked with a speed index ( 235/60ZR15 98Y ) use the above chart Y would be up to 186 MPH