09 June, 2023
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Marion Smith

Decoding Tire Sidewall Markings: A Comprehensive Guide to Reading Tire Sidewalls

Have you ever looked at your tire’s sidewall and wondered what the alphanumeric markings on it mean? The sidewall contains crucial information about the tire size, load capacity, speed rating, and understanding these markings is essential for maintaining and selecting the right tires for your vehicle.

In this comprehensive guide, we will walk you through the process of decoding tire sidewall markings, which will enable you to make informed decisions and ensure optimal performance and safety of your wheels.

How to read a tire sidewall:

Deciphering tire size:

The tire size is typically the first piece of information you'll encounter on the sidewall. It is expressed in a standardized format like P215/65R15. Here's what each element of the tire size means:

"P" denotes the tire's application, indicating it is designed for passenger vehicles. Others include "LT" for light truck tires, and "ST" for special trailers.
"215" represents the tire's width in millimeters, measuring from sidewall to sidewall.
"65" indicates the aspect ratio or profile, representing the sidewall's height as a percentage of the tire's width.
"R" signifies the tire's construction type, usually "radial" for the commonly used modern tires.
"15" denotes the diameter of the wheel in inches that the tire is designed to fit.

Understanding tire size helps you choose the right replacement tires and maintain proper compatibility with your vehicle.

Load Index and Speed Rating:

Next, you'll find two additional alphanumeric codes representing the tire's load-carrying capacity and speed rating. For example, a code like 95S means:

"95" corresponds to the load index, indicating the maximum load capacity the tire can handle, which in this case is 690 kg.

"S" represents the speed rating, indicating the maximum speed at which the tire can operate safely, which in this case is 180 km/h.

Consult your vehicle's manual to ensure that the load index and speed rating of your tires are suitable for your driving needs.

Load Index	Kilograms	Load Index	Kilograms	Load Index	Kilograms
65	290	80	450	95	690
66	300	81	462	96	710
67	307	82	475	97	730
68	315	83	487	98	750
69	325	84	500	99	775
70	335	85	515	100	800
71	345	86	530	101	825
72	355	87	545	102	850
73	365	88	560	103	875
74	375	89	580	104	900
75	387	90	600	105	925
76	400	91	615	106	950
77	412	92	630	107	975
78	78	93	650	108	1000
79	437	94	670

Speed Symbol	Approx MPH	Approx KM/H
Q	99	160
R	106	170
S	112	180
T	118	190
H	131	210
V	149	240
VR	131	210
W	168	270
Y	186	300
ZR	149	240

Treadwear, Traction, and Temperature Ratings:

The sidewall often features three important ratings related to treadwear, traction, and temperature resistance. These ratings are denoted by three-letter codes:

Treadwear Rating:: This number indicates the tire's durability and longevity in comparison to a standard reference tire. For example, a tire with a treadwear rating of 300 will wear three times slower than the reference tire.
Traction Rating:: This letter grade represents the tire's ability to grip the road under wet conditions. Ratings range from AA (highest) to C (lowest), indicating the stopping distance on wet surfaces.
Temperature Rating:: Another letter grade, ranging from A (highest) to C (lowest), signifies the tire's resistance to heat buildup and its ability to dissipate heat effectively.

Consider these ratings when selecting tires that align with your driving style and environmental conditions.

Interpreting the DOT Number:

The "DOT" symbol certifies the tire manufacturer's compliance with the U.S. Department of Transportation (DOT) and provides details about the tire’s manufacturing date and location. Displayed as a string of numbers and letters (which looks something like DOTXXXXXXXX1121) is information about when your tire was manufactured. The last four numbers relate to the date of manufacture, so you can identify the age of your tire. In this example, the date code is 1121 which would mean that the tire was manufactured in the 11th week of 2021.

Tire Manufacturer and Model:

The sidewall of the tire often displays the tire manufacturer's name, logo, or brand. Additionally, you may find the tire model or series name, which provides specific details about the tire's design, intended use, or performance characteristics. Recognizing the manufacturer’s information helps you identify the tire's origin and reputation.

Conclusion:

By understanding how to read the sidewall of a tire, you gain valuable insights into your tire’s specifications and capabilities. Decoding the tire size, load capacity, speed rating, treadwear, traction, temperature ratings, and manufacturer information enables you to select the right tires for your vehicle, ensuring optimal performance, safety, and longevity.