Tire Load Index and Speed Rating Explained

Where to find them

Look at the sidewall, right after the tire size. In 205/55R16 91V, the 91 is the load index and the V is the speed rating. Together they are called the service description.

Our guide to reading a tire sidewall shows where the rest of the markings sit.

What the load index means

The load index is a number you can use to look up the maximum weight a tire can bear when inflated to its maximum pressure. It is a code, not a weight itself.

Continental says the scale runs from 0 to 279. Here are a few sample values from Pirelli's chart:

• 85 is 1,135 pounds (515 kg)
• 91 is 1,356 pounds (615 kg)
• 95 is 1,521 pounds (690 kg)
• 100 is 1,764 pounds (800 kg)

The values are per tire. A higher number means the tire can carry more.

Why you should not go lower

Overloading a tire can damage it and cause it to wear out quickly, or in the worst case lead to a blowout. For that reason, both Pirelli and Continental say never to fit tires with a lower load index than the vehicle maker specifies.

A higher load index than specified is acceptable, according to both. USTMA's guidance is that replacement tires should have the same size, load index and speed rating as recommended by the vehicle or tire manufacturer, and should not be of a smaller size or load-carrying capacity.

Continental says to find the load index your vehicle needs on the tire information placard, usually on the driver's side door jamb. The owner's manual and the sidewall of your original tires are other places to check.

Pirelli says light-truck tires usually show two ratings separated by a slash. The first applies when the tire runs singly. The lower second one applies when it runs as part of a dual-wheel pair. Check the sidewall and the owner's manual.

What the speed rating means

The speed rating is a letter that stands for a maximum speed. Pirelli explains that it reflects the ability of a tire to withstand or dissipate heat at high speeds.

Here are the values from Pirelli's chart:

• S is 112 mph
• T is 118 mph
• U is 124 mph
• H is 130 mph
• V is 149 mph
• W is 168 mph
• Y is 186 mph

Z is also used, and Pirelli lists it as 149 mph and above. Metric values for each letter are in the chart as well.

BFGoodrich notes that ratings range from A (lowest) to Y (highest), with H falling between U and V. That is why the letters do not follow alphabetical order in the list above.

It is not a speed limit

Pirelli is clear that the speed rating should never be taken as the safe maximum speed. Actual safe speed depends on weather, road conditions and the state of the vehicle.

Driving beyond a tire's rating can shorten its life and potentially cause damage that leads to accidents.

Posted limits still apply. The rating is a test result for the tire, not advice on how fast to drive.

Following your vehicle's specification

To find the speed rating your vehicle calls for, Pirelli says to look in the owner's manual for the vehicle maker's recommendation. The rating on your current tires is molded onto the sidewall after the load index.

Your current tires may not be what the vehicle maker specified. Previous owners sometimes change tires. If you are unsure, the door placard and owner's manual are the reference, and a tire professional can confirm.

Because tires on a vehicle usually work as a set, ask a tire professional before you mix tires with different service descriptions on the same vehicle.

How the two fit together

The load index and speed rating describe different limits. One is about weight and the other is about speed.

Pirelli ties the load index to the tire at its maximum inflation pressure, and the speed rating to heat at high speed. Both are tested ratings, set by the tire maker under specific conditions.

You need to match both. A tire can meet the load index your vehicle calls for and still fall short on speed rating, or the other way around.

A worked example

Take the service description 91V.

The 91 is the load index. In Pirelli's chart it corresponds to 1,356 pounds (615 kg) per tire at maximum inflation pressure.

The V is the speed rating. In Pirelli's chart it corresponds to 149 mph.

Neither value is a recommendation for how to drive. They are test-based ratings for the tire.

If a new tire shows a lower number than the one your vehicle maker specifies, that tire is not a match. If it shows a higher number, it is acceptable according to Pirelli and Continental, though a tire professional can confirm.

Common mix-ups

Reading the load index as pounds. It is a code. Look it up in a chart.

Treating the speed rating as a speed limit. Pirelli says it should never be taken as the safe maximum speed.

Choosing by size alone. The load index and speed rating are part of what you are matching, as USTMA's guidance shows.

Adding up the four load indexes. The values are per tire, and they say nothing about the vehicle's own loading limits. Those are in the owner's manual and on the door placard.

Putting it together when you shop

When you read a size from the sidewall or placard, take the whole service description with it. A size such as 225/65R17 is not enough on its own, because the load index and speed rating are part of what you are matching. Continental notes that extra load (XL) tires are built to carry more weight than a standard tire of the same size.

Use the tire finder to see tires and retailers for your size. On each retailer's product page, compare the load index and speed rating with your door placard or owner's manual before you buy.

If you are considering a different size, the tire size calculator shows how the diameter and speedometer reading change. A different size can also change the load index you need, so confirm with a tire professional or the placard. Light-truck sizes like LT265/70R17 use the same kind of service description.