Tire Size Explained: What the Numbers Mean | Les Schwab

Tire Size Explained: What the Numbers Mean

Tire size can be confusing. Some numbers on the sidewall are listed in millimeters while others are inches. Plus, the right size for your car, hand truck, or dawdler can differ depending on where and how you drive .
You can see your original equipment bore size in your owner ’ mho manual or on the placard generally located on the driver ’ s side door jam. This is the sizing recommended by the vehicle manufacturer .
If you ’ ra matter to in switching out your tires for a unlike look or performance, a commodity place to start is the numbers and other indicators on your existing tires ’ sidewall. future, have a run down professional help you determine a bore size range that will fit your vehicle and drive needs .
Tagged diagram of tire size meanings

Tire Size Meanings

Here’s what those numbers and indicators on the sidewall indicate and how to understand them:
A: TIRE TYPE The first letter in the code tells you what class of run down it is .
P stands for passenger vehicle tire. P-class tires include cars, SUVs, crossovers, minivans and smaller pickup trucks .
LT means light truck run down, designed for vehicles that are capable of carrying heavy loads, towing trailers, or for those looking for an supernumerary heavy duty option. These are much equipped on three-quarter or 1 long ton trucks and SUVs .
ST stands for special Trailer. These tire sizes are meant for trailers, including one-fifth wheels and other locomotion trailers, ampere well as gravy boat and utility trailers .
If there ’ s no letter before the first number, you have a metric unit tire most normally referred to as european size. It ’ mho besides measured in millimeters but may have a unlike lode capacity than a P or LT tire .
B: TIRE WIDTH The three-digit total following the letter is the run down ’ randomness width ( from side to side, looking at the bore head on ) in millimeters. This may besides be referred to as the section width .
C: ASPECT RATIO The forward slash separates the bore width number from the two-digit aspect ratio. The bigger the aspect proportion, the higher/taller the bore ’ mho sidewall, or “ visibility ” as it ’ sulfur sometimes called .
The aspect proportion is indicated on the run down sidewall as a share. It ’ s the height of the sidewall measured from steering wheel rim to top of the pace, expressed as a share of tire width .
In this model, the view ratio is 65, meaning the sidewall is 65 percentage vitamin a high as the tire is broad. To get the sidewall stature, take the tire width of 215 mm and convert it to inches ( 8.46 ). then multiply this by 65 % ( .65 ). This gives you an answer of 5.5, the sidewall altitude in inches .
D: CONSTRUCTION TYPE This single letter tells you about the internal construction of the bore .
R is for radial tires, the diligence standard for most tires today. They have better road grip, lower rolling resistance for better gasoline mileage, ride comfort and lastingness than previous generations of tires. In a radial run down, the plies — layers of solid cords made of a blend of polyester, steel and fabric and coated with rubber — are laid vertical to the guidance of travel .
Radial construction tire diagram

D is for tires built with diagonal ( crisscrossed ) plies, called bias-constructed tires. They are besides called conventional, x-ply, or cross-ply tires. Some motorcycle and trailer tires calm use this home construction .
Bias construction tire diagram
Some run-flat tires are identified with an F followed by the type of inner construction .
E: WHEEL DIAMETER This two-digit act specifies wheel diameter in inches. It ’ s the distance between the two beading induct areas ( where a tire gets tightly sealed onto the wheel ) .
How to measure wheel diameter
F: LOAD INDEX The two-digit or three-digit number that follows the gap specifies tire load index. The load index symbol indicates how much weight a tire can support, based on the following standard chart. In our model, the load exponent is 89, which indicates the tire has a load capacity of 1,279 pounds, when inflated to the bore ’ south utmost air pressure rat .
G: SPEED RATING The end letter is the tire speed rat. This indicates the lead rush it ’ randomness safe to travel at for a sustain amount of time. A tire with a higher speed rating can handle heat better and provide more control at faster speeds. The utmost operating amphetamine of a vehicle is no more than the lowest accelerate evaluation of all tires mounted on the vehicle. ( Of course, you should constantly abide by speed limits for safe drive. ) accelerate denounce is normally, but not always, a one letter ( see the graph ) .

Tire Size Charts

Below you will find several charts that will help you understand tire sizing numbers, including a burden index graph and speed rat chart .

LOAD INDEX
LOAD INDEX LOAD (lbs) LOAD INDEX LOAD (lbs) LOAD INDEX LOAD (lbs)
65 639 94 1477 123 3417
66 661 95 1521 124 3527
67 677 96 1565 125 3638
68 694 97 1609 126 3748
69 716 98 1653 127 3858
70 739 99 1709 128 3968
71 761 100 1764 129 4079
72 783 101 1819 130 4189
73 805 102 1874 131 4299
74 827 103 1929 132 4409
75 853 104 1984 133 4541
76 882 105 2039 134 4674
77 908 106 2094 135 4806
78 937 107 2149 136 4938
79 963 108 2205 137 5071
80 992 109 2271 138 5203
81 1019 110 2337 139 5357
82 1047 111 2403 140 5512
83 1074 112 2469 141 5677
84 1102 113 2535 142 5842
85 1135 114 2601 143 6008
86 1168 115 2679 144 6173
87 1201 116 2756 145 6393
88 1235 117 2833 146 6614
89 1279 118 2910 147 6779
90 1323 119 2998 148 6944
91 1356 120 3086 149 7165
92 1389 121 3197 150 7385
93 1433 122 3307    
LOAD INDEX LOAD (lbs)
65 639
66 661
67 677
68 694
69 716
70 739
71 761
72 783
73 805
74 827
75 853
76 882
77 908
78 937
79 963
80 992
81 1019
82 1047
83 1074
84 1102
85 1135
86 1168
87 1201
88 1235
89 1279
90 1323
91 1356
92 1389
93 1433
94 1477
95 1521
96 1565
97 1609
98 1653
99 1709
100 1764
101 1819
102 1874
103 1929
104 1984
105 2039
106 2094
107 2149
108 2205
109 2271
110 2337
111 2403
112 2469
113 2535
114 2601
115 2679
116 2756
117 2833
118 2910
119 2998
120 3086
121 3197
122 3307
123 3417
124 3527
125 3638
126 3748
127 3858
128 3968
129 4079
130 4189
131 4299
132 4409
133 4541
134 4674
135 4806
136 4938
137 5071
138 5203
139 5357
140 5512
141 5677
142 5842
143 6008
144 6173
145 6393
146 6614
147 6779
148 6944
149 7165
150 7385

 

SPEED RATING
  SPEED SYMBOL SPEED (mph)
  A1 3
  A2 6
  A3 9
  A4 12
  A5 16
  A6 19
  A7 22
  A8 25
  B 31
  C 37
  D 40
  E 43
  F 50
  G 56
  J 62
  K 68
  L 75
  M 81
  N 87
  P 93
  Q 99
  R 106
  S 112
  T 118
  U 124
  H 130
  V 149
ZR* W 168
Y 186
(Y) Above 186

Buying New Wheels or Changing Your Tire Size?

A tire size calculator is a quick way to see whether the tire size you ’ rhenium considering will probable fit your cable car, SUV, sports car, light truck or crossing .
But remember that is merely an estimate. It ’ sulfur crucial to stay within the sizing tolerances of your vehicle. Tires that are the wrong size could cause some pull in the guidance bicycle, rub against the suspension or torso of your fomite, reduce clearance on hills, or leave in a starchy or noisier ride.

If you ’ ra considering mounting a unlike tire size on your vehicle, bridle with a tire technical. Find out whether the tires and wheels you have your eye on are the right fit for your fomite ’ sulfur suspension, gearing, and bodywork. And ask how any differences in revolutions per mile, tire travel rapidly, load index, and accelerate rate will affect your drive quality and vehicle operation .
See how new tires and rims will look on your car or truck using our virtual Wheels simulator, available at any Les Schwab .
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