Load Index, Speed Index, Load Range

Tire Load Index & its Load Capacity

The load index is a standardized measurement used globally to ensure that tires are matched correctly to a vehicle's weight requirements – thus acting as a safety threshold that prevents structural failure under stress. It is a numerical code that represents the maximum weight capacity each tire can safely support.

Understanding what the load index on tires means is crucial for vehicle maintenance, as it ensures that you don’t accidentally compromise safety by installing tires with insufficient load capacity.

Tire Speed Index & its Corresponding Speed

A tire’s speed rating indicates the optimal speed that the tire can safely maintain over time. In short, it’s the fastest speed a tire can handle before it no longer performs as designed. The higher the speed rating, the better control and handling you’ll have at higher speeds.

The speed rating system was developed to help control the safe performance of tires at standardized speeds. A tire’s certified speed rating is given a letter from A to Z, ranging from 5km/h (3mph) to above 300 km/h (186 mph).This rating system (see below) shows the top speed for which a tire is certified. It does not indicate the total performance capability of a tire.

Load Range & the Ply-rating

Tire load range refers to the tire’s ply rating and its ability to carry a specified load at a specified air pressure. Historically, this was determined by the number of physical plies in a tire. Today, it’s a standardized rating system that represents strength and load-carrying capacity, not actual ply count.

You'll typically see load ranges labeled as:

• Load Range C (6-ply rating)
• Load Range D (8-ply rating)
• Load Range E (10-ply rating)
• Load Range F and above (for heavy-duty/commercial use)