Tire size deserve to be confusing. Some numbers top top the sidewall are provided in millimeters while others room inches. Plus, the ideal size for your car, truck, or trailer have the right to differ relying on where and also how girlfriend drive.

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You have the right to see her original devices tire dimension in her owner’s hands-on or on the placard usually located top top the driver’s side door jam. This is the sizing recommended by the automobile manufacturer.

If you’re interested in switching the end your tires for a different look or performance, a great place to begin is the numbers and other indicators on her existing tires’ sidewall. Next, have a tires professional help you determine a tires size range that will certainly fit your vehicle and also driving needs.

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Tire dimension Meanings

Here’s what those numbers and also indicators ~ above the sidewall indicate and also how to know them:

A: tire TYPE The an initial letter in the password tells friend what course of tire it is.

P represents passenger auto tire. P-class tires include cars, SUVs, crossovers, minivans and also smaller pickup trucks.

LT method light van tire, designed for vehicles the are qualified of carrying heavy loads, towing trailers, or because that those trying to find an extra hefty duty option. This are frequently equipped on three-quarter or 1 ton trucks and also SUVs.

ST stands for Special Trailer. These tire sizes room meant because that trailers, including fifth wheels and also other take trip trailers, and boat and also utility trailers.

If there’s no letter prior to the first number, you have a metric tire most typically referred to together European size. It’s also measured in millimeters but may have a different load capacity than a p or LT tire.

B: tire WIDTH The three-digit number complying with the letter is the tire’s broad (from next to side, looking in ~ the tires head on) in millimeters. This may also be described as the section width.

C: aspect RATIO The forward cut separates the tire width number from the two-digit facet ratio. The larger the facet ratio, the higher/taller the tire’s sidewall, or “profile” as it’s sometimes called.

The facet ratio is suggested on the tires sidewall as a percentage. It’s the elevation of the sidewall measured native wheel pickled in salt to top of the tread, expressed as a percent of tires width.

In this example, the element ratio is 65, definition the sidewall is 65 percent together high as the tires is wide. To gain the sidewall height, take it the tire width of 215 mm and convert it come inches (8.46). Climate multiply this by 65% (.65). This offers you solution of 5.5, the sidewall height in inches.

D: building TYPE This single letter tells you around the internal construction of the tire.

R is because that radial tires, the market standard for most tires today. Castle have far better road grip, lower rolling resistance for much better gas mileage, ride comfort and durability than previous generations of tires. In a radial tire, the plies — class of strong cords do of a blend of polyester, steel and also fabric and coated v rubber — are laid perpendicular come the direction that travel.

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D is because that tires built with diagonal line (crisscrossed) plies, called bias-constructed tires. Lock are additionally called conventional, x-ply, or cross-ply tires. Part motorcycle and trailer tires still use this interior construction.

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Some run-flat tires are established with one F followed by the type of interior construction.

E: WHEEL DIAMETER This two-digit number specifies wheel diameter in inches. It’s the distance between the 2 bead seat areas (where a tires gets strict sealed top top the wheel).

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F: fill INDEX The two-digit or three-digit number that adheres to the void specifies tire load index. The load index prize indicates exactly how much load a tire can support, based on the following standard chart. In ours example, the pack index is 89, which indicates the tire has a fill capacity of 1,279 pounds, as soon as inflated to the tire’s best air push rating.

G: rate RATING The critical letter is the tire rate rating. This suggests the optimal speed it’s for sure to travel at because that a continual amount of time. A tire with a higher speed rating have the right to handle heat far better and provide much more control at much faster speeds. The maximum operating speed of a car is no much more than the lowest rate rating of every tires an installed on the vehicle. (Of course, friend should always abide by speed limits for more secure driving.) rate rating is usually, yet not always, a single letter (see the chart).

Tire dimension Charts

Below girlfriend will find several charts the will aid you understand tire sizing numbers, including a pack index chart and also speed rating chart.


LOAD INDEXLOAD INDEXLOAD (lbs)LOAD INDEXLOAD (lbs)LOAD INDEXLOAD (lbs)
656399414771233417
666619515211243527
676779615651253638
686949716091263748
697169816531273858
707399917091283968
7176110017641294079
7278310118191304189
7380510218741314299
7482710319291324409
7585310419841334541
7688210520391344674
7790810620941354806
7893710721491364938
7996310822051375071
8099210922711385203
81101911023371395357
82104711124031405512
83107411224691415677
84110211325351425842
85113511426011436008
86116811526791446173
87120111627561456393
88123511728331466614
89127911829101476779
90132311929981486944
91135612030861497165
92138912131971507385
9314331223307
LOAD INDEXLOAD (lbs)
65639
66661
67677
68694
69716
70739
71761
72783
73805
74827
75853
76882
77908
78937
79963
80992
811019
821047
831074
841102
851135
861168
871201
881235
891279
901323
911356
921389
931433
941477
951521
961565
971609
981653
991709
1001764
1011819
1021874
1031929
1041984
1052039
1062094
1072149
1082205
1092271
1102337
1112403
1122469
1132535
1142601
1152679
1162756
1172833
1182910
1192998
1203086
1213197
1223307
1233417
1243527
1253638
1263748
1273858
1283968
1294079
1304189
1314299
1324409
1334541
1344674
1354806
1364938
1375071
1385203
1395357
1405512
1415677
1425842
1436008
1446173
1456393
1466614
1476779
1486944
1497165
1507385


SPEED RATINGSPEED SYMBOLSPEED (mph)
A13
A26
A39
A412
A516
A619
A722
A825
B31
C37
D40
E43
F50
G56
J62
K68
L75
M81
N87
P93
Q99
R106
S112
T118
U124
H130
V149
ZR*W168
Y186
(Y)Above 186

*For tires having a preferably speed capacity above 149 mph, a ZR may show up in the size designation... Above 186 mph, a ZR must appear in the dimension designation, including a Y speed symbol in brackets.


Buying new Wheels or transforming Your tire Size?

A tire size calculator is a quick way to watch whether the tire size you’re considering will most likely fit her car, SUV, sporting activities car, irradiate truck or crossover.

But remember that is just an estimate. It’s important to continue to be within the sizing tolerances of your vehicle. Tires that space the wrong size could cause some traction in the steering wheel, rub versus the suspension or body of your vehicle, alleviate clearance top top hills, or result in a stiffer or noisier ride.

If you’re considering mounting a various tire size on her vehicle, inspect with a tires expert. Uncover out even if it is the tires and also wheels you have your eye on room the right fit for your vehicle’s suspension, gearing, and bodywork. And ask how any type of differences in revolutions per mile, tires speed, load index, and also speed rating will impact your journey quality and also vehicle performance.

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See how new tires and rims will look on your vehicle or truck making use of our virtual Wheels simulator, obtainable at any type of Les Schwab.