Tire Size 235/40r18 vs 245/40r18
While the two sizes may seem quite similar at first glance, even small differences in tire dimensions can have surprising effects on your ride. Let’s take a closer look at what changing from 235/40r18 to 245/40r18 tires really means for your vehicle’s performance, handling, and more.
- Wider tires provide better traction and handling
- Ride comfort may be slightly reduced due to stiffer sidewalls
- Fuel efficiency may decrease marginally
- Speedometer accuracy is minimally affected
- Ground clearance increases slightly with taller tires
Fitment Guide
Since this falls comfortably within the accepted 3% range, switching from 235/40r18 to 245/40r18 tires should be possible without major modifications or issues. However, it’s always wise to double-check your vehicle’s specific clearances to be certain.
On-Road Impact
So how will those wider 245/40r18 tires feel out on the open road? Here are some of the chief differences you might notice:
- Enhanced grip and handling: The larger contact patch of the wider 245 tires provides more rubber on the road, which can boost traction and cornering stability, especially in dry conditions. You may find that your vehicle feels more planted and responsive.
- Slightly stiffer ride: That extra width does come with a bit more sidewall stiffness, so you might experience a slightly firmer ride quality compared to your previous 235 tires. However, many drivers appreciate this more direct road feel.
- Speedometer reads 1.2% high: Because 245/40r18 tires are 1.2% taller, they rotate fewer times per mile than 235/40r18s. This causes your speedometer to read about 1.2% faster than your actual speed. While not a huge difference, it’s something to be aware of.
- Potential for reduced fuel economy: The wider 245 tires create a larger frontal area and may increase rolling resistance somewhat. This could lead to a very slight reduction in gas mileage, although many owners don’t notice a significant difference.
Off-Road Impact
If you venture off the beaten path, here’s what to expect with 245/40r18 tires compared to 235/40r18s:
- Improved flotation and traction: When driving on soft surfaces like sand or mud, the wider footprint of 245 tires can help you stay on top rather than digging in. Combined with the slightly taller sidewall, this may give you an edge in low-traction situations.
- Increased ground clearance: The 0.16 inch (4 mm) taller sidewall of 245/40r18 tires raises your vehicle’s ground clearance by the same amount. While not a massive change, this minor boost can be helpful for clearing small obstacles.
- Enhanced off-road aesthetics: There’s no denying that wider, beefier tires look the part for trail-ready vehicles. The more aggressive stance provided by 245 tires can elevate your rig’s rugged appearance.
235/40r18 vs 245/40r18
| Feature | 235/40R18 | 245/40R18 | Difference |
|---|---|---|---|
| Diameter inches (mm) | 25.4 (645.2) | 25.72 (653.2) | 0.31 (8) +1.2% |
| Width inches (mm) | 9.25 (235) | 9.65 (245) | 0.39 (10) +4.3% |
| Circumference inches (mm) | 79.8 (2026.96) | 80.79 (2052.09) | 0.99 (25.13) +1.2% |
| Sidewall Height inches (mm) | 3.7 (94) | 3.86 (98) | 0.16 (4) +4.3% |
| Revolutions per mile (km) | 793.97 (493.35) | 784.25 (487.31) | -9.72 (-6.04) -1.2% |
| Speedo Reading | 20 mph | 20.25 mph | +0.25 mph |
Difference Between 235/40r18 and 245/40r18 Tires
The primary difference between 235/40R18 and 245/40R18 tires is the width, with 245/40R18 tires being 0.39 inches (10 mm) wider than 235/40R18 tires.
Can I Use 245/40r18 Tires Instead of 235/40r18?
Yes, in most cases you can use 245/40r18 tires in place of 235/40r18 tires. The overall diameter of 245/40r18 tires is only 1.2% larger than 235/40r18 tires, which falls within the generally accepted range of plus or minus 3% for a safe and compatible tire swap.
How Much Taller is a 245/40r18 Tire Than a 235/40r18?
A 245/40r18 tire is 0.31 inches or 8 millimeters taller than a 235/40r18 tire. This translates to the 245/40r18 tire having a 1.2% larger overall diameter.
How Much Wider is a 245/40r18 Tire Than a 235/40r18?
245/40r18 tires have a section width that is 0.39 inches or 10 millimeters greater than 235/40r18 tires. Put another way, 245/40r18 tires are 4.3% wider than their 235/40r18 counterparts.
Our Observations
After weighing the differences, we believe switching from 235/40r18 to 245/40r18 tires offers several benefits with limited downsides for most drivers.
The 1.2% change in diameter is unlikely to cause major issues for odometer accuracy, gearing, or clearance. Meanwhile, the additional width provides tangible improvements in grip, handling, and off-road capability.
Unless you’re extremely sensitive to small changes in ride quality or fuel economy, stepping up to 245/40r18 tires can be an excellent way to enhance your vehicle’s performance and style without complications.
Of course, always do your research to ensure proper fitment for your specific make and model. But in most cases, moving from 235/40r18 to 245/40r18 tires is a smart and straightforward upgrade for both on and off-road driving.
Asma Akter is the lead writer at Tiresizecompare.com, bringing her expertise to the automotive industry. With a strong background in technical writing and a passion for clear communication, Asma excels at breaking down complex tire-related information for readers. Her work helps consumers make informed decisions about tire sizes and compatibility, contributing to safer and more efficient vehicle operations.
