Tire Size 235/40r18 vs 245/40r18

The main difference between 235/40R18 and 245/40R18 tires is the section width. This means the 245/40R18 tire is 10 millimeters wider than the 235/40R18 tire. The section width is the width of the tire from sidewall to sidewall.

Tire 1 Front View
Width
Dia.
Tire 2 Front View
Width
Dia.
Tire 1 Side View
Tire 1 Wheel
circumference 1
Circ.
Rim
Wall
Revs/Mile
Tire 2 Side View
Tire 2 Wheel
Circ.
Rim
Wall
Revs/Mile
/ R
/ R
Parameter235/35 R18205/40 R18Differ.
Tire Height
Section Width
Circumference
Sidewall Height
Revolutions
Rim Size

 

Fitment Guide

Replacement tires should be within 3% of the original size to prevent clearance issues. The 245/40R18 is 4.3% wider than the 235/40R18, so it may rub or require modifications on some vehicles designed for narrower tires.

Larger tires like 245/40R18 may require a suspension lift or leveling kit to increase clearance for proper fitment.

Ground Clearance

With a diameter of 25.72 inches, the 245/40R18 provides 0.31 inches (8mm) more ground clearance than the 235/40R18 at 25.4 inches.

This extra clearance is useful for off-road driving over obstacles and rough terrain. However, the larger 245/40R18 diameter causes a slightly lower speedometer reading than the 235/40R18 one.

235 40r18 in inches

Gas Mileage

The 245/40R18 wider tread and larger overall diameter increase rolling resistance and rotational mass compared to the 235/40R18.

This results in marginally reduced fuel efficiency for the 245/40R18. The 235/40R18 would provide slightly better gas mileage for daily driving and long trips.

Ride Comfort

The 245/40R18 taller sidewall flex subtly improves ride quality over cracks and bumps.

The extra sidewall cushioning absorbs more road impacts, leading to a smoother ride than the 235/40R18. The difference is slight but may be noticeable on very uneven pavement.

Aesthetics

Visually, the 245/40R18 slightly taller sidewall gives it a subtly “stretched” look compared to the 235/40R18 shorter sidewall.

Some vehicles suit this aesthetic better than an overly low-profile appearance. Overall, the taller profile 70 suits trucks and SUVs well.

235 40r18 in inches

Handling & Stability

The 235/40R18 shorter sidewall enhances responsiveness and handling precision versus the 245/40R18. The extra flex in the 245/40R18 sidewall reduces handling sharpness slightly. However, both deliver responsive, stable handling for everyday driving.

Noise & Vibration

With a shorter, stiffer sidewall, the 235/40R18 transmits more road noise and vibration into the cabin. The 245/40R18 additional sidewall flex helps absorb noise and vibration, leading to a marginally smoother, quieter ride. But differences are minor – both are relatively quiet.

Durability & Wear

The narrower 235/40R18 may exhibit slightly more even tire wear across the tread. The wider 245/40R18 stresses suspension components due to increased weight, potentially accelerating the wear of other parts like wheel bearings.

Adverse Conditions

Both tires perform similarly in rain, snow, and off-road conditions. The 245/40R18 added ground clearance gives it a slight advantage off-road, while the 235/40R18 shorter sidewall improves responsiveness. Overall, both handle adverse conditions well.

Speedometer Difference

At an actual speed of 20mph, the speedometer reads 20.25mph with 245/40R18 tires versus 20.00mph with 235/40R18 tires.

This 0.25mph higher reading with the larger 245/40R18 tires should be considered to avoid unintentionally speeding.

What Does 235/40r18 Mean?

The tire size 235/40R18 is a standard way of expressing specific information about a tire. Here’s what each part of the code represents:

  • 235: This number represents the width of the tire in millimeters. In this case, the tire is 235 millimeters wide.
  • 40: This number is the aspect ratio, the ratio of the tire’s height to its width. In this example, the height is 40% of the tire’s width.
  • R: This letter indicates that the tire has a radial construction.
  • 18: This number represents the diameter of the wheel (rim) in inches.

235/40r18 vs 245/40r18

235/40r18 vs 245/40r18

This table will provide you with a quick and easy way to understand the differences between the options.

Our Observation
The differences between 235/40R18 vs 245/40R18 tires are relatively minor. The 245/40R18 offers slightly more ground clearance and a smoother ride, making it a good choice for trucks and SUVs where that extra cushioning is beneficial.

However, the 235/40R18 provides crisper handling and better fuel efficiency thanks to its shorter, narrower footprint – ideal attributes for responsive daily driving.

Overall, we’d recommend the 235/40R18 for most sedans and daily drivers and the 245/40R18 for larger vehicles where that extra sidewall flex improves comfort and capability. But either tire size will deliver strong overall performance.

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