Tire Size 235/40r18 vs 235/45r18
Swapping out your tires can be a big decision, with implications for both on-road performance and off-road capability. We’ll dive into the details of switching from a 235/40R18 to a 235/45R18 tire, exploring the key differences and their real-world impacts.
- Greater sidewall height for improved ride comfort
- Reduced revolutions per mile for potentially better fuel economy
- Speedometer will read slightly lower than actual speed
- Increased ground clearance by about 0.46 inches
- Potentially improved traction due to larger contact patch
- May affect handling characteristics slightly
- Ensure proper fitment for your vehicle before switching
Fitment Guide
According to the data provided, the diameter difference between these two tire sizes is 0.93 inches (23.5 mm), which represents a 3.6% increase.
This falls within the recommended 3% range, meaning the 235/45R18 tire is a suitable replacement for the original 235/40R18 tire without requiring any major adaptations or modifications.
On-Road Impact
The increased sidewall height of the 235/45R18 tire can have a noticeable impact on the vehicle’s on-road performance.
This change may result in a slightly softer and more compliant ride quality, as the taller sidewall can help absorb more road imperfections and provide a more cushioned feel.
Additionally, the slight increase in overall tire diameter can slightly affect the speedometer accuracy, causing the speedometer to read approximately 0.73 mph (1.17 km/h) higher at a true speed of 20 mph (32.19 km/h).
Off-Road Impact
When it comes to off-road performance, the increased sidewall height of the 235/45R18 tire can provide a small but potentially beneficial boost in ground clearance.
This extra clearance may be helpful when navigating over obstacles or traversing uneven terrain. However, the overall impact on off-road performance is likely to be relatively minor, as the difference in tire size is relatively small.
235/40r18 vs 235/45r18 Table
Here’s a detailed comparison of the tire sizes 235/40R18 and 235/45R18 to help you understand the difference.
| Feature | 235/40R18 | 235/45R18 | Difference |
|---|---|---|---|
| Diameter inches (mm) | 25.4 (645.2) | 26.33 (668.7) | 0.93 (23.5) +3.6% |
| Width inches (mm) | 9.25 (235) | 9.25 (235) | 0 (0) 0% |
| Circumference inches (mm) | 79.8 (2026.96) | 82.71 (2100.78) | 2.91 (73.83) +3.6% |
| Sidewall Height inches (mm) | 3.7 (94) | 4.16 (105.75) | 0.46 (11.75) +12.5% |
| Revolutions per mile (km) | 793.97 (493.35) | 766.07 (476.01) | -27.9 (-17.34) -3.5% |
| Speedo Reading | 20 mph | 20.73 mph | +0.73 mph |
Can I Use 235/45R18 Instead of 235/40R18?
Yes, you can generally use a 235/45R18 tire as a replacement for a 235/40R18 tire. The 3.6% difference in diameter falls within the recommended 3% range, so the 235/45R18 is a suitable replacement without requiring any major adaptations or modifications.
How Much Taller Is a 235/40R18 Tire Than a 235/45R18?
The 235/45R18 tire is 0.46 inches (11.75 mm) taller than the 235/40R18 tire. This represents a 12.5% increase in sidewall height between the two tire sizes.
What is the Difference Between 235/40R18 and 235/45R18?
The most significant difference between these two tire sizes is the sidewall height. The 235/45R18 tire has a sidewall that is 0.46 inches (11.75 mm) taller than the 235/40R18 tire, which equates to a 12.5% increase in sidewall height.
Our Observation
The switch from a 235/40R18 to a 235/45R18 tire represents a relatively modest change in terms of both on-road and off-road performance.
The increase in sidewall height can provide a slightly more comfortable ride and a minor boost in ground clearance, while the speedometer inaccuracy is within a manageable range.
Overall, the differences are relatively small and may not significantly impact most drivers’ daily experiences, making this a reasonably straightforward tire upgrade that should not require any major adaptations or modifications to the vehicle.
Caitlin McCormack is a lead writer at Tiresizecompare.com and a trusted guide at AmarCalculator. With an extensive background in finance and mathematics, she simplifies complex calculations and delivers precise insights. Caitlin’s expertise ensures readers receive accurate and reliable information to make informed decisions. Her passion for numbers and dedication to clarity make her an invaluable resource for tire comparisons.
