Higher vs Lower: What is a Tyre Speed Rating?

A tyres speed rating is the maximum speed it is designed to handle, whilst carrying its recommended load capacity. Based on controlled testing, the manufacturer will have determined that the tyre can safely support this weight whilst maintaining speeds up to this maximum level.

You should always equip your vehicle with tyres that carry the correct speed rating, as specified within the owner’s manual. 

Where can I see my tyre speed rating?

You can find the speed rating on the sidewall of the tyre itself, as part of the alphanumeric markings. It is the final part of the code represented by a single letter.

For example, in the code 225/50R17 94T, the letter “T” indicates the speed rating.

Tyre Speed Rating Chart

How is a tyre speed rating calculated?

Tyre manufacturers set up specific lab testing environments, to calculate the tyres speed rating. Typically the tests involve:

• Set Conditions: The tyre is mounted on a test wheel and run on a drum to simulate contact with the road. The test wheel and drum are set up in a way which further simulates the effects of load weight, putting the tyre under the same level of pressure in the process. For uniformity and benchmarking, the test environment is usually temperature controlled as well.
• Speed Evaluation: The wheel is gradually accelerated in increments of 10 km/h (6.2 mph), every 10 minutes, until the tyre reaches its maximum speed. If the tyre fails or becomes significantly deformed, the previous speed used is set as the overall speed rating.

High Speed Rating Tyres

When tyres are being designed, engineers will seek to achieve higher speed ratings by working on the tyres ability to dissipate heat (generated by friction between the tyre and road surface). Higher speed rating tyres are made from materials which can handle more heat, and have tread patterns designed to promote cooling in addition to structural reinforcements, to prevent deformation.

If you’re looking for tyres with a high speed rating, you should consider the following:

• Bridgestone Potenza S001
• Pirelli P Zero
• Michelin Pilot Sport 4 S
• Continental ContiSportContact5
• Dunlop SP SportMaxx RT
• Goodyear Eagle F1 Asymmetric 5

Can I fit tyres with a higher speed rating?

Can I switch to a tyre with a higher speed index?

As long as the tyres are the correct size for your wheels, you can absolutely fit those which have a higher speed rating that your vehicle requires. This is not only perfectly legal, but you won’t need to inform your insurance company either.

Is a higher speed rating better?

Providing you don’t mind paying the price premium that typically comes with higher speed ratings, you can benefit from the improved vehicle handling, cornering, stopping power and steering response, all provided by higher speed rating tyres.

Can I fit tyres with a lower speed rating?

With the exception of specially marked winter tyres (see below), it is illegal to fit tyres with a lower speed rating than what has been specified by your vehicle manufacturer. In the UK, drivers can face a fine of up to £2,500 and 3 penalty points on their licence for each illegal tyre.

In addition to this, you run the risk of tyre failure, steering and handling issues, and reduced safety for yourself, passengers and other drivers on the road.

Choosing a lower speed index for winter tyres

Providing the tyres are marked M+S or 3PMSF, you can fit winter tyres which have a lower speed rating than the maximum speed of the car (or as indicated in the vehicles user manual).

This is legal providing you affix a sticker to the vehicle (which is in the driver’s field of vision) indicating the maximum speed of the tyres, which also must be adhered to when driving.

You should also consider the effects on:

• Durability: Tyres with a lower speed rating may suffer from increased wear and tear
• Handling: The vehicle is likely to respond differently as a result
• Insurance: You should check the fine print for any allowances which include using winter tyres at lower speed ratings. Generally using tyres with a lower speed index will invalidate your car insurance.

Low Speed Rating Tyres

You may find tyres with a lower speed rating than your vehicle under our Winter Tyres range. Remember that you must follow the steps (as detailed above) in order to keep your vehicle road legal.

For more advice on fitting your vehicle with various speed rating tyres, head over to our blog post ‘Can you fit tyres with different speed ratings?’ here.

In Summary: Why is tyre speed important?

To conclude, understanding tyre speed ratings is crucial for maintaining optimal vehicle safety, performance, and compliance with the law. Tyre speed ratings are designed to ensure your tyres can handle the speed and load demands of your vehicle effectively. Choosing the right tyre speed rating, as specified in your owner’s manual, not only provides the best driving experience but also reduces risks associated with improper tyre use. While higher speed rating tyres can improve handling and performance, it’s important to balance these benefits with cost and necessity. Always make informed decisions when selecting tyres, especially if you are considering options outside the manufacturer’s recommendations, to ensure your vehicle remains roadworthy and safe.