Tire Size 225/45r18 vs 245/40r18

The width is the primary difference between the 225/45r18 and 245/40r18 tire sizes. The 245/40r18 has a wider width of 9.65 inches (245mm), which is about 8.2% more than the 225/45r18 tire width of 8.86 inches (225mm). This increased width can lead to better traction and stability but also affect fuel efficiency and ride comfort.

225/45r18 vs 245/40r18 Table

Feature 245/40r18 225/45r18 Difference
Overall Diameter 25.72″ 25.97″ 0.26″
Width inches 9.65″ 8.86″ 0.79″
Circumference 80.79″ 81.59″ 0.8″
Sidewall Height 3.86″ 3.99″ 0.13″
Revolution 784.25 776.52 7.73
Rim Size 18″ 18″ Same
Rim Width Range 8.0-9.5″ 7.0-8.5″ Different

Overall Diameter
The 225/45r18 tire has a diameter of 25.97 inches, slightly larger by 1% (0.26 inches) compared to the 245/40r18 tire. A larger diameter generally offers more ground clearance, which is advantageous in off-road driving or rough terrain. It also results in a lower speedometer reading.

Conversely, a smaller diameter tire reduces ground clearance, potentially leading to vehicle damage on rough roads, but will result in a higher speedometer reading. The 1% difference falls within the recommended 3% difference from the factory recommended tires, making both options viable.

Section Width
The 245/40r18 tire is approximately 8.2% wider than the 225/45r18 tire. A wider tire generally provides improved traction due to a larger contact patch, enhancing grip during acceleration, braking, and cornering.

However, wider tires often generate more road noise due to increased contact area. Conversely, a narrower tire like the 225/45r18 has less surface area in contact with the road, potentially reducing grip in wet or slippery conditions.

The circumference of the 225/45r18 tire is marginally larger by 1% compared to the 245/40r18 tire. An increased circumference will result in lower speedometer readings, whereas a decreased circumference will result in higher speedometer readings.

Revolutions Per Mile
The 225/45r18 tire completes fewer revolutions per mile, potentially leading to an extended lifespan due to reduced wear and tear. Conversely, the 245/40r18 tire completes more revolutions per mile, which might increase wear and shorten its lifespan. However, the difference is only 1%, which might not significantly impact the tire’s lifespan.

Sidewall Height
The 225/45r18 tire has a 3.3% taller sidewall than the 245/40r18 tire. A taller sidewall absorbs more bumps and road irregularities, providing a smoother ride and increased traction on snowy or icy roads. Conversely, a shorter sidewall on the 245/40r18 tire may lead to a harsher ride but offers a sportier and more aggressive look.

Rim Size
Both tires can be mounted on 18″ rims, although the recommended rim widths differ. The 245/40r18 tire can accommodate rims of widths 8.0-9.5″, making them more suitable for a sportier, aggressive look.

On the other hand, the 225/45r18 tire accommodates a narrower rim range (7.0-8.5″), giving them a more classic or conservative appearance.

How much taller is a 245/40r18 tire than a 225/45r18?

The height of a 245/40r18 tire is 25.72 inches (653.2 mm), whereas the height of a 225/45r18 tire is 25.97 inches (659.7 mm). This makes the 225/45r18 tire approximately 0.26 inches (or 6.5 mm) taller than the 245/40r18 tire.

How much wider is a 245/40r18 tire than a 225/45r18?

Regarding width, the 245/40r18 tire measures 9.65 inches (245 mm) wide, and the 225/45r18 tire measures 8.86 inches (225 mm) wide. Consequently, the 245/40r18 tire is about 0.79 inches (or 20 mm) wider than the 225/45r18 tire.

Can I use 245/40r18 instead of 225/45r18?

The overall diameter of a 245/40r18 tire is 25.72 inches, whereas the 225/45r18 tire has a diameter of 25.97 inches. The difference between these two sizes is roughly 0.26 inches or about 1%. Given this is less than the suggested 3% variance, it may be possible to use a 245/40r18 tire instead of a 225/45r18.

Can I put a 245/40r18 on a 225/45r18?

The 245/40r18 tire has a rim width range of 8.0-9.5″, while the 225/45r18 tire has a range of 7.0-8.5″. The two ranges overlap at 8.0-8.5″, which suggests that it might be possible to mount a 245/40r18 tire on a rim intended for a 225/45r18 tire.

Our Observation
The choice between the 225/45r18 and 245/40r18 largely depends on your driving conditions and personal preferences. The 225/45r18 tire, with its larger diameter, higher sidewall, and smaller width, offers a smoother ride and potentially a longer lifespan, ideal for everyday, comfortable driving.

Conversely, the 245/40r18 tire, with its wider tread and smaller sidewall, provides better traction and a sportier look, making it suitable for performance-oriented drivers.

Remember, while both options fall within the recommended diameter difference, always consult a tire professional or your vehicle’s manufacturer before changing your tire size to ensure safety and performance.

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