# Tire Size 305 FAQ

If you’re looking for information about tire size 305, you’ve come to the right place. This FAQ guide is designed to answer common questions about tires with a width of 305 millimeters. Keep reading to learn more about tire size 305 and how to choose the right tire for your vehicle.

**What Size Is A 305 Tire?**

A 305 tire is a tire with a section width of 305 millimeters. The tire’s size is generally expressed as a series of numbers, such as 305/xx/Ryy, where “xx” represents the aspect ratio and “Ryy” represents the wheel diameter in inches.

In this format, 305 refers to the tire’s width in millimeters, measured from sidewall to sidewall. The aspect ratio (xx) is a percentage that indicates the height of the tire’s sidewall relative to its width. The wheel diameter (yy) is the wheel size the tire is designed to fit.

**How Wide Is A 305 Tire In Inches?**

To convert a 305 tire’s section width from millimeters to inches, you can use the following conversion factor: 1 inch = 25.4 millimeters.

So, a 305 tire’s width in inches would be: 305 millimeters / 25.4 (mm/in) =12.01 inches. Thus, a 305 tire is approximately 12.01 inches wide.

**How Tall Is A 305 Tire?**

To determine the overall diameter of a 305 tire, you need the aspect ratio and the wheel diameter as well. Assuming you have the aspect ratio (xx) and wheel diameter (yy), you can calculate the overall diameter using the following formula: Overall Diameter = (2 * (section width * aspect ratio / 100)) / 25.4 + wheel diameter.

Let’s say you have a tire size of 305/35R20:

- Calculate the sidewall height: 305 * 0.35 = 106.75 millimeters
- Convert the sidewall height to inches: 106.75 / 25.4 ≈ 4.20 inches
- Calculate the overall diameter: (2 * 4.20) + 20 ≈ 28.40 inches

In this example, the overall diameter of a 305/35R20 tire is approximately 28.40 inches. Please note that this calculation is an approximation and might vary slightly between different tire manufacturers and models.

**Are 35 Inch Tires The Same As 315?**

YES, 315-wide tires are the same as 35” tires although they can be close in size, depending on the aspect ratio and rim diameter. “315” represents the tread width in millimeters, while “35” denotes the tire’s diameter in inches.

To compare the overall diameter of a 315 tire to a 35-inch tire, we need the full tire size, including the aspect ratio and rim diameter, expressed as 315/XX/YY, where XX is the aspect ratio and YY is the rim diameter in inches.

For example, let’s calculate the height of a 315/70/17 tire:

- Measure the exact sidewall height: Multiply the tread width (315 mm) by the sidewall height (70%) to get 220.5 mm. Since a tire has two sidewalls, multiply 220.5 mm by 2 to get a total sidewall height of 441 mm.
- Convert the rim diameter to metric: Convert the 17-inch rim diameter to millimeters by multiplying it by 25.4, resulting in 431.8 millimeters.
- Calculate the overall tire diameter: Add the total sidewall height (441 mm) and the rim diameter (431.8 mm) to get 872.8 mm.

To find the tire diameter in inches, divide the total diameter (872.8 mm) by 25.4. This results in approximately 34.4 inches, which is close to 35 inches but different.

**Can I Put 305 Tires On 275 Rims?**

It is possible to replace 275 tires with 305 ones. However, before making any alterations to your vehicle’s tire dimensions, consult the doorjamb or owner’s manual to verify that the new size aligns with your vehicle’s specifications and performance needs.

A tire sized 275/65r18 has a mounting rim width range of 8-10 inches, while a 305/70r18 tire has a range of 9-11 inches. As evidenced by the overlapping rim width ranges, you can indeed use a 275 tire size on a 305 tire size rim, or vice versa.

Do note that the 305 tire has a slightly larger circumference, causing the speedometer to display a marginally lower speed than the actual rate for any given engine.

**305 Tire Rim Width**

The recommended rim width range for a tire size of 305/xxRyy will depend on the aspect ratio (xx) and rim diameter (yy) specified in the tire size. For example, for a tire size of 305/35R20, the recommended rim width range would be between 9.0 and 11.0 inches.

It’s important to follow the recommended rim width range specified by the tire manufacturer to ensure proper fitment, handling, and tire performance.