Tire Size 305/70r18 vs 35×12.50r18
The main difference between the 305/70r18 and 35×12.50r18 tire size lies in the section width. The 305/70r18 tires have a narrower width of 12.01 inches compared to 12.52 inches for 35×12.50r18 tires. This 4.3% width difference impacts various performance factors.
| / | R |
| / | R |
| Parameter | 235/35 R18 | 205/40 R18 | Differ. |
|---|---|---|---|
| Tire Height | |||
| Section Width | |||
| Circumference | |||
| Sidewall Height | |||
| Revolutions | |||
| Rim Size |
Fitment Guide
The 35×12.50r18 tire is 0.6% larger in overall diameter versus the 305/70r18. This minor size difference means 35×12.50r18 can directly replace 305/70r18 tires without fitment issues. Larger variations beyond 3% may require lift kits or other modifications.
Ground Clearance
The 35×12.50r18 offers 0.22 inches (5.48mm) more ground clearance due to its slightly larger diameter. This extra clearance can help prevent scrapes and damage when driving over rugged terrain, rocks, tree roots, or other obstacles.
It provides a slight advantage for off-road use. However, the difference in ground clearance between the sizes is minor in practical terms.
Gas Mileage
The wider and heavier 35×12.50r18 may have slightly more rolling resistance, decreasing fuel efficiency marginally compared to the 305/70r18.
With 4.3% more section width and 1.3% greater sidewall height, the 35×12.50r18 presents more rubber to flex and deform, increasing energy loss.
It also has more rotational mass. While the difference is modest, the 305/70r18 would likely confer a small fuel economy benefit.
Ride Comfort
The 35×12.50r18 offers a subtly smoother ride thanks to its additional 0.11 inches of sidewall height. This provides more cushioning and insulation from impacts and road irregularities.
However, both tires deliver very comparable comfort and compliance. For most drivers, any difference would be difficult to discern.
Aesthetics
Visually, the two tires are nearly indistinguishable. The 35×12.50r18 has a barely perceptible increase in sidewall height compared to the 305/70r18, but the difference is minor.
Subjectively, both tires provide a balanced look appropriate for most trucks and SUVs without appearing undersized or over-inflated.
Handling & Stability
Performance in dry conditions is equivalent between the two. The barely taller 35×12.50r18 sidewall results in fractionally slower turn-in response.
But both tires deliver responsive, stable handling with no noticeable difference in real-world driving. Their on-road manners and capabilities are very comparable.
Noise & Vibration
Again, differences are marginal. The 35×12.50r18 dampens noise and vibration slightly better, thanks to its marginally taller sidewall and greater air volume. But both transmit minimal noise or vibration, providing a refined ride. Cabin comfort is similar between the two.
Durability & Wear
With nearly identical diameters, both tires should exhibit comparable wear across the tread surface. The 305/70r18 slightly smaller contact patch could confer a subtle advantage in terms of longevity.
But real-world tread life would be very similar between the two sizes. Both also provide the load-carrying durability expected of a heavy-duty 18-inch truck tire.
Adverse Conditions
Performance in rain, snow, mud, sand, and off-road conditions is comparable between the two. The 35×12.50r18 offers a tiny traction edge in deep mud or sand due to its wider tread.
But both sizes deliver capable traction and hill climb ability expected of an aggressive all-terrain tire.
Speedometer Reading
At an actual speed of 20 mph, the 305/70r18 displays a speedometer reading of exactly 20 mph.
But the marginally larger 35×12.50r18 turns the speedometer 0.12 mph lower at the same actual speed. This minuscule difference has no practical impact on real-world driving.
What Does 305/70r18 Tire Mean?
The first number in tire size, such as 305, tells you the tire’s width in millimeters. The second number, 70, tells you the aspect ratio. The aspect ratio is the height of the tire’s sidewall expressed as a percentage of the width.
In this case, 70 means the sidewall is 70% as tall as the tire’s width. The last number, 18, is the rim diameter in inches. The “r” stands for radial, which is the type of tire.
Our Observation
The real-world differences between 305/70R18 and 35×12.50R18 tire sizes are minor. Both fit and perform well on most full-size trucks and SUVs for on-road and light off-road use.
The 35×12.50R18 does offer a touch more ground clearance and sidewall cushioning. However, its larger size could slightly hinder fuel economy and handling responsiveness. Overall, either dimension serves as a versatile, capable option for drivers not pursuing hardcore off-roading.
The selection comes down to personal preference for aesthetics, capabilities, and pricing. Realistically, most customers will be happy with their vehicle’s ride, handling, and capability running either tire size.
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.
