Tire Size 225/45r18 vs 245/40r18
The difference between 225/45r18 and 245/40r18 tires is the width. The 245/40r18 is 0.79 inches wider than the 225/45r18 tire. This wider tread provides some advantages and disadvantages compared to the narrower 225 width.
| / | R |
| / | R |
| Parameter | 235/35 R18 | 205/40 R18 | Differ. |
|---|---|---|---|
| Tire Height | |||
| Section Width | |||
| Circumference | |||
| Sidewall Height | |||
| Revolutions | |||
| Rim Size |
Fitment Guide
When replacing tires, the new set should be within 3% of the overall diameter of the original tires to avoid clearance issues or speedometer inaccuracy.
The 245/40r18 tire diameter is 1% smaller than the 225/45r18. So, the 245/40r18 should not cause major fitment problems as a replacement tire. However, the wider 245 tread width may require checking for rubbing at full lock.
Ground Clearance
The 225/45r18 tire has a diameter of 25.97 inches, while the 245/40r18 is slightly smaller at 25.72 inches. This 0.25-inch reduction in overall height marginally decreases ground clearance.
The lower profile 245/40r18 is more likely to scrape or sustain damage over rough roads or obstacles. This clearance reduction can be detrimental to off-road driving.
Gas Mileage
The 245/40r18’s wider tread results in a larger contact patch with the road than the 225/45r18. This increased rolling resistance can slightly reduce fuel efficiency.
The heavier 245 tire also has more rotational mass versus the lighter 225. Overall, the narrower 225/45r18 should confer a minor gas mileage benefit over the 245/40r18.
Ride Comfort
The 245/40r18’s shorter, stiffer 40 aspect ratio sidewall transmits more road impacts into the cabin than the 225/45r18’s more cushioning 45 aspect ratio.
The 225/45r18 absorbs bumps better, providing a more compliant ride. This difference is amplified over very uneven pavement.
Aesthetics
Subjectively, the lower profile design of the 245/40r18 looks more aggressive and sporty than the taller 225/45r18 sidewall.
However, the difference is subtle and comes down to personal preference. Both sizes suit most vehicles well visually.
Handling & Stability
The 225/45r18’s taller sidewall promotes more flex, reducing handling precision slightly compared to the 245/40r18.
The shorter, stiffer 40 aspect ratio sidewall of the 245/40r18 gives sharper turn-in and handling response. But both tires deliver responsive, stable handling for everyday driving.
Noise & Vibration
The 225/45r18’s more flexible sidewall absorbs road impacts and vibrations better. This dampens noise transmission into the cabin compared to the 245/40r18.
However, both tires are relatively quiet and smooth at highway speeds.
Durability & Wear
The 225/45r18’s narrower tread distributes forces over a more minor contact patch, promoting even wear. The 245/40r18’s wider tread wears more along the outer shoulders.
Even rotation helps maximize longevity for both. Overall, tread life is similar between sizes with proper maintenance.
Adverse Conditions
Performance in rain, snow, and off-road is comparable between sizes. The 245/40r18’s shorter sidewall gives a slightly better response in snow, but it is also more prone to damage from obstacles due to the lower profile.
The 225/45r18 maintains a traction advantage thanks to better ground clearance.
Speedometer Difference
Due to its slightly smaller overall diameter, the 245/40r18 tire results in a lower speedometer reading than the 225/45r18 at any given true vehicle speed.
For example, at an actual speed of 20 mph, the speedometer reads 19.8 mph with the 245/40r18 but 20 mph with the 225/45r18. This 0.2 mph speedometer difference is minor.
245/40r18 vs 225/45r18
You can quickly grasp the differences by referring to the comparison table.
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.
How Much Taller Is A 225/45r18 Tire Than A 245/40r18?
The 225/45r18 tire stands 0.26 inches (6.5 mm) taller than its 245/40r18 counterpart, indicating a 1% diameter difference.
The 245/40r18 tire measures 25.72 inches (653.2 mm) tall, whereas the 225/45r18 tire is 25.97 inches (659.7 mm) tall.
How Much Wider Is A 245/40r18 Tire Than A 225/45r18?
The width of the 245/40R18 tire exceeds that of the 225/45R18 by 0.79 inches (20mm), marking an 8.9% increase.
The 245/40R18 measures 9.65 inches (245mm) wide, while the 225/45R18 is narrower at 8.86 inches (225mm) wide.
What Does 225/45r18 Mean?
The tire size 225/45R18 indicates a tire with a width of 225 millimeters, aspect ratio of 45%, and designed for an 18-inch rim.
This alphanumeric code provides essential information about the tire’s dimensions and compatibility. The tire size 225/45r18 is equivalent to 25.9×8.9R18 in inches.
What Does 245/40R18 Mean?
The tire size 245/40R18 indicates a tire with a width of 245 millimeters, an aspect ratio of 40%, and is designed for an 18-inch rim.
This alphanumeric code details the tire’s dimensions and intended wheel size. The 245/40R18 tire size is equal to 25.7×9.6R18
Our Observation
The key differences between 225/45r18 and 245/40r18 tires lie in ride comfort, ground clearance, and fuel efficiency.
The 225/45r18 absorbs bumps better thanks to a taller sidewall, increases ground clearance with its larger overall diameter and offers minor fuel economy benefits from lower rolling resistance.
In contrast, the 245/40r18 has a sportier, lower-profile look, with a stiffer sidewall that prioritizes handling over comfort.
While performance is similar overall, priorities like ride quality, off-road clearance, and gas mileage may dictate preference between these two tire sizes that are broadly comparable. Evaluating intended use and required trade-offs helps determine the optimal choice.
Meet Caitlin McCormack, a Tire Size Expert and Blogger Passionate About Everything Related to Tires. With Years of Experience in the Tire Industry, Caitlin Has Become an Expert in Tire Sizes and Their Impact on Vehicle Performance.
