| Spec | Old | New | Diff |
|---|---|---|---|
| Diameter | 600.6 mm | 614.6 mm | 14 mm |
| Revs/km | 530 | 518 | -12 |
This tire size is within the safe range. Your handling will remain stable.
When your speedometer shows 100 km/h, you are actually traveling at 102.33 km/h.
As a Senior Automotive Tire Engineer, I often encounter questions about tire sizing, especially when two sizes appear very similar at first glance. Today, we're going to delve into a classic comparison: the 175/70 R14 and the 185/70 R14. While they share a rim diameter and aspect ratio, the subtle difference in tread width can lead to distinct performance characteristics and suitability for various driving needs. Understanding these nuances is crucial for optimizing vehicle performance, safety, and driver satisfaction.
Before we jump into the comparison, let's quickly re-establish what each part of a tire size designation signifies. This fundamental understanding is key to appreciating the engineering implications of our two contenders:
With both tires sharing the '70 R14' designation, our primary focus will naturally be on the impact of the 10mm difference in section width.
This 10mm difference directly impacts the tire's contact patch – the area of rubber that touches the road. A wider tire (185mm) generally means a larger contact patch. This has several direct implications for vehicle dynamics:
Both tires have an aspect ratio of 70. This means the sidewall height is 70% of their respective section widths:
Despite the same aspect ratio, the 185mm tire will have a slightly taller sidewall (7mm taller, to be precise) due to its greater width. This subtle difference can influence:
The overall diameter of the tire is calculated as: Rim Diameter + (2 * Sidewall Height). Let's convert the 14-inch rim diameter to millimeters (14 inches * 25.4 mm/inch = 355.6mm).
The 185/70 R14 tire has an overall diameter that is approximately 14mm larger than the 175/70 R14. This is a crucial point for speedometer calibration. If a vehicle was originally fitted with 175/70 R14 tires and then switched to 185/70 R14 without speedometer recalibration, the speedometer would read slightly lower than the actual speed. For instance, at an indicated 100 km/h, the vehicle would actually be traveling around 102.3 km/h (185/175 = ~1.023). While this difference might seem small, it's an important engineering consideration for compliance and safety.
As an automotive tire engineer, my primary recommendation is always to adhere to the vehicle manufacturer's specified tire sizes, load indexes, and speed ratings. These specifications are determined through extensive testing to ensure optimal safety, performance, and vehicle dynamics. While switching from a 175/70 R14 to a 185/70 R14 might seem like a minor change, it can affect speedometer accuracy, ABS/ESC system calibration, and potentially even fender clearance if the vehicle wasn't designed for it. Always consult your vehicle's owner's manual or a qualified tire professional before making any changes.
In summary, while both the 175/70 R14 and 185/70 R14 are solid choices for smaller vehicles, the 10mm difference in width creates distinct characteristics. The 175mm leans towards efficiency and aquaplaning resistance, while the 185mm offers a slight edge in grip and handling. Your ultimate decision should align with your driving style, priorities, and most importantly, your vehicle's engineered requirements.