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How to Read your Tire Sidewall


We are halfway through the year which means that winter is right around the corner! Is your car winter ready? Let's take a look at your tires for starters. Winter tires can make your commute a smoother process. If you do not have winter tires that are up to the Rubber Manufacturers Association mud and snow standards you will have to temporarily replace them. The size and type of tire you have on your vehicle can alter your vehicles performance dramatically. There are so many options when choosing new tires so its important to understand all the markings on tires when making a purchase.

Importance of correct tires:

The size and type of tire you have on your vehicle can alter your vehicles performance dramatically. With that being said ensure that you use the same type of tire all around your vehicle. You cannot interchange between all season and winter tires, doing so will affect your car's performance and will put your safety at risk. Also remember that when purchasing tires, all season tires are not the same as winter tires. All season tires can be used for winter but they will perform poorly. You don't want to increase the risk of driving in the snow by using the wrong type of tire. If you live in areas with harsh winter conditions it is recommended to invest in summer tires and winter tires respectively. Don't forget to also interchange your summer rims to winter rims and vice versa. Chrome wheels, such as those on luxury lines like BMW, don't do well in the winter and should be switched to steel wheels.

Tire pressure:

PSI stands for pounds per square inch. This is the measurement created to know the proper inflation of your tires. The proper PSI for your vehicle and tires is located in your Owners' Manual. This measurement is important because it allows your vehicle to handle better. If the tires are not properly inflated the tires will wear unevenly and thus shorten the lifespan of your tires.

When the tires are inflated to the correct PSI, you improve your gas mileage and increase the lifespan of your tires, not to mention a smoother drive. Tire pressure should be checked at least once a month.

How to read your tire sidewall:

Now that we covered the basics its always good to know how to read your tire. Let's get to it!

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The first item you will come across should be a letter. It will either state “P” for Passenger tire which is used for anything between sedans, compact cars and anything up to light trucks. If it shows an “LT” the tire was made for light trucks all the way to full ton trucks.

The second item you will see will be three digits for example: “325”. This sequence of numbers is stating the SWT (section width tread) of the tire. It is the width of the tire from one sidewall to the other sidewall, measured in millimeters.

Following the three digits is a two digit number such as: “65” called the Aspect Ratio. The aspect ratio or the profile is the height of the sidewall.

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The aspect ratio is followed by a letter, in this case it is “R”. This stands for Radial Construction which is the design of the tire. The majority of tires are made with radial construction.

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The first stamp will be a two digit number stating the diameter of the wheel. For example, this tire is stamped with an “18” meaning the wheel must be 18” in diameter in order for it to fit. If the tire is stamped with "17" it means your rim should be 17" in diameter. Don't forget to give us a call if you need assistance locating your stock wheels. 

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The following item should be a number for example: “121” this is the Load Index. It tells us the max load capacity per tire. Keep this number in mind when making a tire purchase. Tires should only be replaced with the same or higher load index than the stock tires.

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The next item to look for is a letter. This letter will tell you the Speed Rating of your tires. In this example it is stamped with an “R”. If we look at a speed rating chart letter “R” tells us not to exceed over 106mph. You can cause damage to the tire if the speed is exceeded.

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The last two items are markings to look out for just to ensure the tires are up to standards. The first stamp is called the DOT. DOT (U.S. Department of Transportation Marking) is a series of numbers marking the wheel safe for sale.

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 The last marking only applies to winter wheels. The lettering looks like the following “M+S”. If your tire is labeled with this marking it is stating that it meets the Rubber Manufacturers Association standards for mud and snow.

You are now ready to go tire shopping and prepare for the winter to come. Use our easy guideline and video to direct you in the right direction.

Have a safe winter!

Silvia –

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