Tyre Load Index

A tyre load index is a numerical code etched onto the car tyre indicating the maximum weight a car tyre can safely carry at maximum speed when inflated. It is generally a two or three-digit code provided by the tyre manufacturer to indicate the maximum load-bearing limit of each tyre.

You can find your tyre size load index on your car tyre’s sidewall markings. These markings will be in letters and numbers, showing different tyre specifications. The tyre load index is displayed as a two or three-digit number after the wheel diameter.

For example, if your tyre marking looks like this: 205/55 R16 91V, ‘91’ would be your tyre load index, with the V representing the speed rating. So the load index in tyres is usually the last digit displayed on your tyre markings.

The sidewall markings can give you your car tyre's entire manufacturing history with just a few letters and numbers. These markings can also be helpful when selecting a tyre for your car.

The sidewall markings found on your car tyre indicate:

• Tyre Width

• Aspect Ratio

Wheel Diameter

• Tyre Load Index

• Speed Rating

Along with additional markings like:

• Tyre Type

• Tyre Construction

• ECE Approval Mark and Number

• Tyre Pressure Information

• Tread Wear Indicators

• Production Date

Expanding on the previous section, knowing the meaning of your tyre markings can give you information on the tyre usage specifications and could be helpful when you eventually need to replace your car tyres.

Using the same example, 205/55 R16 91V, let us look at what this information tells us:

- Tyre Width: The number ’205’ tells us the car tyre width in millimetres and is measured from sidewall to sidewall. So this means that the tyre is 205 mm wide.

- Aspect Ratio: The number ‘55’ indicates the height of the tyre sidewall as a percentage of the tyre's width. This is known as the tyre's aspect ratio. So ‘55’ indicates that the sidewall height between the top of the tyre and the rim is 55% of the tyre width.

- Wheel Diameter: ‘R16’ shows the tyre construction (R) and wheel diameter (16). The wheel diameter is the size of the inner rim in inches, on which the tyre is designed to fit.

- Tyre Load Index: The number ‘91’ indicates the tyre load index. It is the tyre's maximum carrying capacity in kilograms. In this case, a tyre with a load index of 91 can carry 615 kg of weight when inflated.

- Speed Rating: The speed rating is represented by the letter V in the marking ‘91V’. The speed rating is the maximum speed of a tyre when it is properly inflated and operating under load. It is the letter shown at the end of the sidewall after the tyre load index.

For this example, the tyre shows a speed rating of ‘V’, which indicates that it has a maximum speed of 240 km/h.

You should note that tyre load indexes and speed ratings should be looked at together when buying a new tyre. Moreover, you should also match your tyre's speed rating with your car's speed capabilities.

When buying car tyres or examining your own car tyre, you will note that there are additional markings accompanying the sidewall markings. These usually indicate the recommended use of the tyre.

• Tyre Type:

This is indicated by a letter that precedes the tyre width. Different letters denote different types of tyres and their intended function. For example,

• P or No Letter: Indicates a passenger car tyre.

- LT: Indicates a light truck.

- C: Indicates a commercial van tyre.

- XL, HL, or Reinforced: Indicates tyres with a higher load capacity than normal for their dimensions. These tyres must be replaced by the same tyre types. For example, HL tyres must be replaced with other HL tyres.

- T: Indicates temporary or spare tyres.

- Tyre Construction:

The letter before the wheel diameter indicates the tyre's internal construction. The letter 'R' from the marking ‘R16’ in the previous example stands for Radial. Almost every tyre constructed today is a radial tyre.

- ECE Approval Mark and Number:

An ECE mark indicates that your tyre meets all tyre regulations in its sidewall markings and conforms to the standards of the United Nations Economic Commission for Europe (UNECE). To obtain an ECE approval mark, the tyre must be certified in a laboratory and pass conformity tests and pass quality control testing done while in the manufacturing plant.

Not all tyres are subject to this certification, so tyres used and manufactured outside of Europe have their own country's certifications. For example, in India, tyres follow the BIS ISI certification scheme.

- Tyre Pressure Information:

This is indicated by the markings 'MAXLOAD' and 'MAXPRESS', which detail the tyre's maximum load (tyre load index) and maximum pressure. Note that these are not your car's load and pressure values. To ensure your tyres are working correctly, check your car owner's manual, the sticker on the driver's door or the fuel filler cap sticker for your car's recommended tyre inflation pressures.

- Tread Wear Indicators:

The letters' TWI' on your tyres show the location of your tyre's tread wear indicators. These indicators are narrow elevations across/perpendicular to your tyre's longitudinal grooves. In most EU countries, the minimum tread depth is 1.6 mm.

A simple way to deduce the condition of your tyre’s tread is by checking to see if the tyre's tread and the indicators are level with each other. If they are levelled, then it is time to replace your tyres.

This is because tyres with little tread depth provide poor grip during rain and snow.

- Production Date:

Your tyre's production date is printed next to the DOT (Department Of Transportation) marking on your tyre's sidewall. The last four numbers indicate the manufacturing year, and the first codes are primarily US market code requirements.

The first two digits of the last four numbers indicate the week of manufacturing, and the last two numbers indicate the manufacturing year.

For example, if the DOT code is DOT 6l Y5 006X 1218, the last four digits - 1218 represent the manufacturing/production date of the tyre.

12 is the number of weeks, and 18 is the year. So the tyre was manufactured and rolled out between May 20th, 2018, and March 31st, 2018.

Car tyres are not designed for loads of any size, so you must know your car tyre load index and ensure you do not exceed it. This is because overloading the tyre causes various problems and safety concerns, leading to reduced tyre traction and increasing the risk of tyre blowouts.

To calculate the tyre load capacity when picking out a car tyre, you must consider the car weight, passenger and cargo weight, and the recommended tyre pressure. You must also buy all four tyres of the same load capacity to equally distribute weight on all four wheels of your car.

You can always use tyres with a higher tyre load index than your factory tyres, but never ones with a lower load index. The typical tyre load index for most passenger cars and light trucks ranges from 70 to 110.

An easier way to do this would be to refer to a load index chart for tyres. These can be found online or provided by the tyre manufacturer. It states the tyre's maximum load capacity in relation to the tyre load index.

The speed rating is denoted by a letter immediately after the tyre load index. When replacing your car tyres, you must know the tyre load index and speed ratings of your factory tyres and need to match or improve them even if you do not plan on pushing the stated limits.

This is done to keep your car's performance consistent, and using tyres with the wrong tyre load index and speed rating can affect the speed and performance of your car.

You must also never fit a tyre with a lower speed rating than the one on your car's factory tyres. This is because the car tyre turns faster at higher speeds, generating more heat. Not using the right tyres to cope with the extra heat can cause them to burst, which is a serious safety concern when the car is in motion.

You should also note that the tire speed rating isn't the same as the recommended travel speed. Speed ratings are a product of laboratory testing. So tyre speed ratings will always exceed the maximum highway speed limits.

n winter, tyres face more weather challenges. Driving becomes more difficult, and braking distances become longer. As a result, winter tyres often have a lower speed rating (Q), and if the tread depth or wheel diameter differs, the tyre would also have a different tyre load index.

So it is important to check the tyre load indexes and the speed rating when picking out winter tyres to ensure you are not overloading them. This is because higher loads mean less control over your car. This is especially dangerous in winter as cars are more prone to skidding.

• Exceeding the tyre load index can overload your tyres which can cause the sidewalls to crack and deform, wear out the tire much faster, and cause premature tyre failure.

• The tyres can overheat, which can increase the risk of blowouts. The excess weight can also damage the tyre's tread and rims.

• Overloading the tyres can cause them to burst when the car is in motion. This is a serious safety concern as you can lose control of your vehicle and end up crashing or causing an accident.

• Your tyres can fail to meet safety regulations, resulting in penalties and fines. This can also affect your car insurance claim approvals and reimbursements if you were involved in an accident.

• It can reduce the tyre's traction, causing issues when turning corners and braking. The increased weight can also make your brakes less effective and increase braking distances.

• It can affect your car's performance, especially when driving on inclines (e.g., over hills) and when accelerating. Furthermore, it can cause increased noise and vibrations when driving and damage the car's suspension.

Most four-wheeler insurance plans do not explicitly cover tyre damages, so before purchasing, always compare car insurance policies to check for exclusions.

However, comprehensive car insurance policies do provide add-on covers that offer increased coverage to certain parts of your car for a slightly higher premium. A Tyre Protection Cover is one of them.

This cover can be purchased with a stand-alone own-damage plan or with a comprehensive car insurance plan. It covers tyre replacement costs, labour costs associated with repairs, and protection after an accident.

Car tyres are often the most overlooked part of a car. They form the foundation on which your car rests, offering stability and a smooth driving experience. Exceeding the tyre load index or using tyres with the wrong specifications can heavily impact your car's drivability and safety, increasing the risk of accidents.

However, now that you know what a tyre load index is, combining this knowledge and buying a car insurance policy with a tyre protection cover will offer you maximum coverage and tyre protection.