Tyre Speed Rating Distance
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A speed rating is a letter code (such as H, V, W, or Y) assigned to a tire indicating the maximum speed it's certified to sustain safely under proper load and inflation conditions for an extended period, not just briefly. Higher letters correspond to higher rated speeds.

It typically estimates how far or how long a tire could theoretically be driven at or near its rated maximum speed, often used to illustrate the standardized test duration/distance manufacturers use to certify the rating, rather than a real-world recommendation to drive at that speed for that distance.

Some drivers assume a brief excursion above the rated speed is harmless since the tire doesn't fail instantly, but sustained heat buildup from exceeding the rating — even without immediate failure — degrades the tire's structure and increases the risk of a delayed blowout, sometimes well after the speed event.

A tire's speed rating is certified alongside a specific load index, and running at or near maximum load while also approaching the top of the speed rating compounds heat generation, since both increase internal stress and temperature. The rating assumes proper inflation and load, not an overloaded or underinflated tire.

Manufacturers generally recommend matching speed ratings across an axle at minimum, and ideally across all four tires, because mismatched ratings mean the vehicle's actual safe top speed is limited by its lowest-rated tire, and handling balance can be affected by mixing tires with different performance characteristics.