What Tire Size Is 315? (Metric vs. Imperial MM)?

Tires, the foundation upon which every car rides, come in a dizzying array of sizes and specifications. This myriad of options is presented in two dominant systems: Imperial (inches) and Metric (millimeters), often leading to confusion for many vehicle owners.

So, if you’ve ever wondered whether a 35-inch tire is the same as a 315 tire, you’re certainly not alone. This article aims to simplify this complex matter by dissecting and comparing these two tire sizing systems.

Are 35-Inch Tires The Same As 315’s (Metric vs. Imperial MM)?

In the automotive world, tire size nomenclature can be as confusing as it is essential. When comparing the metric system (used by most of the world, including tire manufacturers) and the imperial system (still prevalent in countries like the U.S.), the numbers don’t always translate as you might expect.

In this context, a tire labeled as ‘315’ refers to its width in millimeters (mm) as per the metric system. On the other hand, a ’35-inch’ tire doesn’t denote its width but rather its outer diameter or height.

To equate these two measurements, a conversion is required. But here’s the catch: without knowing other elements such as the aspect ratio and wheel diameter, a direct conversion can be misleading. This is because a 35-inch tire doesn’t necessarily have a width of 315mm; its width could be more or less, depending on its aspect ratio (the ratio of the height of the tire’s cross-section to its width).

To put it simply, a 35-inch tire is not always the same as a 315 tire. The former speaks to the height or outer diameter of the tire, while the latter talks about the tire’s width. The actual dimensions can vary based on the aspect ratio and wheel diameter, which are essential components of a tire’s specification.

So, next time you’re considering tire sizes, remember that it’s not as simple as converting inches to millimeters or vice versa. Understanding the measurements mentioned on the tire sidewall will provide a comprehensive picture of the tire size and help you make the most informed decision for your vehicle.

Stay tuned for more such insights into the world of automobiles. Up next, we will be discussing why it’s essential to choose the correct tire size for your vehicle, how tire sizes impact performance, and much more.

A photo of a pickup truck on the road.

Fitting 35-Inch Tires On Your Truck

Have you ever thought about fitting 35-inch tires on your truck? Whether it’s for improved off-road performance, ground clearance, or just for aesthetics, making such a move requires careful consideration. Here’s what you should know about the process.

Lift Kit

The first step in fitting 35-inch tires on your truck is usually installing a lift kit. A lift kit raises the truck’s body or suspension, providing the necessary clearance for larger tires. For 35-inch tires, a lift of 4 to 6 inches is often needed, although this can depend on the make and model of your truck. Lift kits vary in complexity and cost, and installation can be a sizable project.

Wheel Offset

Wheel offset is another critical consideration when upgrading to larger tires. The offset is the distance from the wheel’s mounting surface to the centerline.

A positive offset means the mounting surface is towards the front (outside) of the wheel, and a negative indicates it’s towards the back (inside). Fitting 35-inch tires may require wheels with a negative offset to prevent the tires from rubbing against the suspension components.

Fender & Arch Trimming to fit 35’s

Even with a lift kit and the right wheel offset, some trucks may require additional modifications to accommodate 35-inch tires. This could mean trimming the fenders or wheel arches.

This modification ensures that the tires have enough room to move during suspension articulation, particularly while off-roading. It’s a significant step that alters the truck’s appearance and should be done professionally to maintain a clean look and prevent rust.

Will The 35’s Throw Out Your Speedo?

One less obvious impact of fitting larger tires is that it can throw off your speedometer. The speedometer in your truck is calibrated based on the diameter of the stock tires.

When you increase the tire size, the speedometer may read slower than your actual speed because the larger tires cover more ground in one revolution. You can recalibrate your speedometer after fitting larger tires, either by using a handheld tuner or having the adjustment done professionally at a service center.

A man driving in the countryside.

What Does 315 70 17 Convert To?

A tire size of “315 70 17” refers to the width, aspect ratio, and wheel diameter in millimeters and inches, respectively. Let’s break down what these numbers mean.


This is the width of the tire in millimeters. To convert it into inches, we divide by 25.4 (since 1 inch equals 25.4 mm), giving us a width of approximately 12.4 inches.


This is the aspect ratio of the tire, represented as a percentage. It’s the ratio of the height of the tire’s cross-section to its width. In this case, the height of the tire’s cross-section is 70% of 315 mm. To calculate it in inches, we have to take 70% of the tire’s width (in inches) and get approximately 8.68 inches.


This represents the wheel diameter in inches. This tire is designed to fit on a 17-inch wheel. However, the overall diameter of the tire isn’t given directly in this notation. We calculate this by adding the diameter of the wheel and twice the height of the tire (since the height is present on both the top and bottom of the wheel).

This gives us approximately 33.4 inches. So, a 315/70R17 tire converts to a tire that is approximately 12.4 inches wide with an overall diameter of approximately 33.4 inches, fitting on a 17-inch wheel.

What Size Rim For A 315 Tire?

When considering rim size for a tire, the most critical factor is the last number in the tire size – the diameter (given in inches in the metric system). The tire you’ve mentioned is “315,” which speaks about the tire width in millimeters but doesn’t provide the necessary information to specify the rim size.

If we take the example above (315/70R17), the “17” indicates that this tire is designed to fit on a 17-inch rim. The width of the rim can vary, but a good general rule is that the tire’s width (in this case, 315mm or 12.4 inches) should be matched with a rim width of approximately 90% of the tire’s width. Therefore, a 315 tire would typically fit well on a rim with a width of around 11 to 12 inches.

However, always refer to the tire manufacturer’s specifications and recommendations for the exact rim width, as they can vary depending on the tire’s specific design and intended use.

Close-up photo of wheels and rims of a BMW car.

Will A 315 Fit On A 10.5 Rim?

A 315 tire, which is approximately 12.4 inches wide, can fit on a 10.5-inch rim. However, it’s a bit narrower than ideal. Ideally, the rim width should be about 90% of the tire width. For a 315 tire, this comes out to a rim width of about 11 to 12 inches.

So while a 10.5-inch rim can support a 315 tire, it may not be the optimal size, potentially affecting the tire’s performance and wear characteristics. It’s always recommended to follow the tire manufacturer’s specific guidelines for rim width.

Can You Put A 315 Tire On A 9.5 Inch Rim?

While it’s technically possible to mount a 315 tire on a 9.5-inch rim, it’s not advisable. The 9.5-inch rim is quite narrower than the ideal rim width for a 315 tire (about 11 to 12 inches). Mounting such a wide tire on a narrow rim can lead to a range of problems. It may compromise the tire’s structural integrity, cause uneven tire wear, and negatively impact the handling and performance of your vehicle.

Can You Fit 315 On An 11-Inch Rim?

Yes, a 315 tire can fit comfortably on an 11-inch rim. This combination aligns quite well with the general rule that the rim width should be about 90% of the tire width. An 11-inch rim is within the recommended rim width for a 315 tire (which translates to approximately 12.4 inches wide), and this setup should ensure a good balance between performance, handling, and tire wear.

In all cases, it’s important to note that the vehicle’s make and model, tire aspect ratio, and intended use (street use, racing, off-roading, etc.) can influence the ideal tire and rim combination. Therefore, always refer to the vehicle and tire manufacturer’s recommendations when selecting tires and rims.

Why Is It Important To Consider The Aspect Ratio When Converting Tire Sizes From The Metric To The Imperial System?

The aspect ratio plays a crucial role in determining a tire’s physical characteristics. It’s the height of the tire’s sidewall expressed as a percentage of its width. When converting tire sizes from the metric to the imperial system, not considering the aspect ratio can lead to incorrect interpretations of the tire’s dimensions.

The aspect ratio, in conjunction with the tire’s width, determines the height of the tire’s sidewall. This, when added to the rim diameter, gives us the overall diameter or height of the tire. Misjudging the aspect ratio can lead to inaccuracies in the overall tire size, affecting vehicle clearance, ride comfort, and performance.

How Does Wheel Offset Impact The Fitting Of Larger Tires Such As 35-Inch Ones?

Wheel offset is the distance from the wheel’s mounting surface to its centerline. It can be positive (the mounting surface is towards the front/outside of the wheel) or negative (towards the back/inside). When fitting larger tires, like 35-inch ones, the wheel offset becomes critical.

A negative offset will push the wheel outwards, providing more clearance between the tire and suspension components, thereby helping accommodate larger tires. However, this can put more strain on the suspension and alter the vehicle’s handling characteristics.

How Does The Speedometer Get Affected By Fitting Larger Tires, And How Can This Be Corrected?

When you fit larger tires, the speedometer may show a slower speed than the actual speed you’re driving at. This discrepancy occurs because the speedometer is calibrated based on the revolutions per minute (RPM) of the stock tires. Larger tires have a greater circumference, which means they cover more ground per revolution, thereby affecting the speedometer reading.

To correct this, the speedometer needs to be recalibrated, either by using a handheld tuner or by taking your vehicle to a professional service center. This recalibration adjusts the speedometer to accommodate the larger tire size, ensuring accurate speed readings.

What Are Potential Drawbacks To Trimming The Fenders Or Wheel Arches When Fitting Larger Tires?

Trimming the fenders or wheel arches can provide additional clearance needed for larger tires. However, it’s a significant alteration that comes with some drawbacks. Firstly, it permanently changes the vehicle’s appearance, which might affect its resale value.

Secondly, if not done professionally, it can result in sharp edges that could damage the tires or lead to rust if the metal isn’t properly sealed. Additionally, it could potentially compromise the structural integrity of the vehicle.

What Factors Should One Consider When Choosing A Lift Kit For Their Vehicle To Accommodate Larger Tires?

Choosing the right lift kit for your vehicle is not just about getting enough clearance for the larger tires. It’s also about maintaining or enhancing the vehicle’s ride quality and handling characteristics. There are several factors to consider. First is the type of lift kit – suspension lift kits provide better performance but are more complex and expensive than body lift kits.

The amount of lift is another critical factor – it should be enough to clear the larger tires, but not so much as to excessively raise the center of gravity and compromise stability. Lastly, the installation complexity and cost should be taken into account, as well as the potential need for additional modifications, like adjusting the gear ratio or drive shaft length.


In conclusion, fitting larger tires on a vehicle is a complex process that requires careful consideration of various factors including vehicle handling, performance, safety, legality, and even aesthetics. It’s crucial to understand the implications of such modifications and to seek professional advice to ensure the modifications are done correctly and safely.

Whether it’s for improved off-road performance, ground clearance, or aesthetics, a well-informed approach will ensure you achieve your goals while maintaining the safety and integrity of your vehicle. Happy modding!

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About Brock Rangel

Hi, I am Brock, and I am the lead editor/photographer for TheCarColony. I have been a mechanic for over 14 years now, and I am here to spread my car knowledge across the web!