305/35R21 in Inches

Understanding the dimensions of the 305/35R21 tire size in both metric and imperial units of measurement is an essential part of tire maintenance and replacement. Let us take a closer look at every important aspect of the 305/35R21 tire to understand what these numbers represent and how they may affect your vehicle's performance.

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What is 305/35R21 in inches?

When we convert 305/35R21 to inches, it is equivalent to 29.4x12R21 tire size in the high flotation system. 305/35R21 tires have a diameter of 29.4" (747 mm), a tread width of 12" (305 mm), and can be mounted on a wheel with a diameter of 21" (533 mm). The sidewall of the tire is 4.2" (107 mm), and the tire's circumference is 92.3" (2346 mm). This means a 305/35R21 tire will make 686 revolutions per mile, or 426 revolutions per kilometer.

305/35R21 Section Width
12"
29.4"
305/35R21 Tire Side
Tire Circumference
92.3"
21"
4.2"
686 Revs/Mile
Metric Inches
Tire Diameter 747 mm 29.4"
Tread Width 305 mm 12"
Aspect Ratio 35%
Rim Diameter 533 mm 21"
Sidewall Height 107 mm 4.2"
Circumference 2346 mm 92.3"
Revolutions 426 per km 686 per mile

How to read 305/35R21 tire size?

Reading a tire size such as can be broken down into three main parts: tread width, aspect ratio and rim diameter.

305 is the width of the tire in millimeters from sidewall to sidewall when it's fully inflated and not under any load. In this example, the tire is 305 millimeters wide.

35 represents the height of the tire's cross-section as a percentage of its width. It means the height is 35% of the tire's width.

R denotes that tire has radial construction.

21 is the diameter of the wheel that the tire fits on, measured in inches. This tire would fit on a 21-inch wheel.

How to convert 305/35R21 to inches

The 305/35R21 conversion is very simple. There are 25.4 millimeters in an inch. All we have to do is divide tread width and sidewall height by 25.4 to convert to inches.

To convert the tire width to inches, you divide 305 mm by 25.4, yielding a tire width of approximately 12 inches. To find the sidewall height in inches, you calculate 35% of the tire width in millimeters (305 mm), convert this figure to inches as before, resulting in a sidewall height of about 4.2 inches. However, to understand the tire's overall diameter, you need to consider the height of two sidewalls and the diameter of the wheel it fits. Therefore, you multiply the sidewall height by 2 and add the wheel diameter (21 inches), giving you an overall tire diameter of approximately 29.4 inches.

So, when converted to inches, 305/35R21 tire is 12 inches wide, 29.4 inches tall, and fits 21-inch rims.

How wide is a 305/35R21 tire?

Tire width, also known as section width, is a measurement in millimeters that indicates the width of a tire from one sidewall to the other. It is the first number provided in a tire's size specifications. 305/35R21 tire has a width of 12 inches or 305 mm.

A greater tire width can increase the tire's contact patch with the road, potentially improving grip and handling. However, wider tires can also increase rolling resistance, which could negatively impact fuel efficiency.

Tire Width
Tread width: 12"

How tall is a 305/35R21 tire?

Tire height, also known as the tire's diameter or overall diameter, is the measurement from the ground to the top of the tire. It's essentially the distance from one side of the tire to the other, passing through the center, when it's correctly inflated and not under load. 305/35R21 tire has a diameter or height of 29.4 inches or 747 mm.

Tire Diameter
Tire height: 29.4"

305/35R21 Tire Sidewall Height

Tire sidewall height, also known as the tire's aspect ratio, is the measurement of the height of the tire's cross-section or the height of the tire from the rim to the tread. It is typically represented as a percentage of the tire's width. 305/35R21 tire has a sidewall height of 4.2 inches or 107 mm.

Sidewall height (also known as tire profile) can greatly affect a tire's driving characteristics. Lower profile tires (30 or 35 series) often provide better handling but can give a harsher ride, while higher profile tires (65 or 70 series) generally provide a smoother ride but with less precise handling.

Tire Sidewall Height
Sidewall height: 4.2"

What size rim fits a 305/35R21 tire?

The rim diameter refers to the diameter of the wheel on which a tire is mounted. It is the distance from one edge of the rim to the opposite edge, passing through the center of the wheel. 305/35R21 tire can be mounted on 21-inch wheels.

The rim diameter is crucial not only for fitting the tire properly but also plays a role in determining the overall performance of the vehicle, including its handling and ride quality.

Rim Diameter
Rim diameter: 21"

305/35R21 Tire Circumference

Tire circumference refers to the distance around the outer edge of a tire. It is the measurement of the entire circumference or perimeter of the tire when it is inflated and mounted on a wheel. 305/35R21 tire has a circumference of 92.3 inches or 2346 mm.

Tire Circumference
Tire circumference: 92.3"

How many revolutions does a 305/35R21 tire make?

Tire revolutions refer to the number of complete rotations a tire makes while the vehicle is in motion. It is a measure of the distance covered by the tire. 305/35R21 tire completes 686 revolutions per mile or 426 revolutions per kilometer.

Tire revolutions are often used in various calculations related to vehicle dynamics, such as determining the distance traveled, estimating fuel consumption, or calculating the speed of the vehicle based on the rotation of the tires. Tire revolutions can also be tracked or monitored by certain vehicle systems, such as the anti-lock braking system (ABS) or the vehicle's onboard computer, for various purposes.

Tire Revolutions
Tire revolutions: 686 per mile

More 21-inch Tire Conversions

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