Find your tyre size and learn what the numbers mean
- A tyre's size is found by looking at the sequence of letters and numbers written on the tyre sidewall. For the below description we will use the example 185/55 R15 81H
- Width - The first 3 digit number (185 in example below) is your tyre width measured in millimetres.
- Profile - The next two digit number (55 in the example below) is the tyre's profile. This measurement is taken from the wheel to the outer circumference of the tyre and the number is a percentage of your tyre's width of 185mm.
- Rim Diameter - The next two digit number is the diameter of the wheel rim measured in inches. The example below has a tyre that is 15 inches.
- Load Index - The next two digit number is the Load index that uses a reference table to find the load capacity of the tyre in kilograms (shown below).
- Speed Rating - the final letter refers to the speed rating which also uses a reference table to indicate the maximum speed for the tyre in kilometres (shown below).
What tyre design is better for my vehicle?
Directional design: For wet performance
Benefits : Good water dispersal
Good wet weather stability
Note : Higher tyre noise (for designs with wide grooves)
Front to rear rotation only
Symmetrical design: For comfort (quieter ride)
Benefits : Usually designed for quieter ride and comfort
Note : For the everyday driver
Asymmetric design: All rounder performance
Benefits : Combination of wet performance and comfort
Ease of rotation
High speed and cornering stability
Note : A little of both
Glossary of tyre jargon
- Reinforced Tyres: Tyres where the manufacturer has added extra strength the side wall to handle more weight e.g. for heavier vehicle
- Run-Flat: Tyres which allow a driver to continue a journey in the event of low or no tyre pressure. Please note that Run flats are designed to run for short distances and should be replaced as soon as possible.
- Speed Rating: The standardised index which is used to indicate the maximum speed a tyre can sustain carrying the specified load in the load index under the conditions specified by the tyre manufacturer.
- Air Pressure: This is essentially the volume of air inside the tyre; it can be measured in either pounds per square inch PSI or bar. Having the correct pressure for tyres is a key factor in Tyre Safety and can usually be found in the Vehicle handbook as well as the fuel cap flap.
- Alignment: This is essentially the correct vertical alignment of the tyres. Generally describes the checks and corrects made to the suspension and steering systems of the vehicle to ensure compliance with the manufacturers recommendations
- Alloy Wheels: Alloy wheels differ from normal Steel wheels because of their lighter weight, which improves the steering and the speed of the car. Alloy wheels are also better heat conductors than steel wheels, improving heat dissipation from the brakes, which reduces the chance of brake failure in more demanding driving conditions.
- Balancing: This is the process for compensating for slight variations in tyre and wheel assembly. By ensuring weight is equally distributed when the tyres and wheels spin, any abnormal vibrations can be eliminated.
- Profile: The height of the tyre side wall expressed as a percentage of the tyres width.
- Rim: The metal edge of the wheel on which the bead is seated supporting the tyre.
- Rim Size: The diameter of the rim (usually measured in inches and also known as the wheel size).
- Rim Width: The Distance between the 2 opposite inside edges of the rim flanges.
- Retreading: This is the process of replacing the tread layer on a tyre. Usually reserved for commercial, agricultural and industrial tyres.
- Speed Rating: The standardized index which is used to indicate the maximum speed a tyre can sustain.
An alphabet representing the maximum speed of this tyre
||180 km/h (112 mph)
||190km/h (118 mph)
||200 km/h (124 mph/)
||210 km/h (130 mph)
||240 km/h (149 mph)
||270 km/h (168 mph)
||300 km/h (186 mph)
How much air should I put in my tyres?
- Proper inflation is the single most important part of tyre care. The inflation pressure on the side of the tyre is the MAXIMUM operating pressure. It is not necessarily the right inflation for your vehicle. Always use the inflation recommended by the vehicle manufacturer.
- You can find it in your owner's manual, posted on the edge of the driver's door, on a door post or on the inside of the glove box door. Always check inflation when tyres are COLD: when the vehicle has been driven less than a mile or one hour or more after driving.
- Use a good quality tyre gauge.
- Note: It's natural for radial tyres to have a slight bulge in the sidewall at their proper inflation pressure.
- Check or adjust inflation every few weeks, before any long trip or if travelling with a heavy load And don't forget to check the spare.
Minimum legal tread depth
- The main reason a tyre has tread is to disperse water efficiently. The less tread you have, the more likely you are to skid or aquaplane on wet roads and lose steering control
Getting the most benefit from your tyres
- Keep the pressure up: The right tyre inflation pressure for your car can be found in the car manufacturer’s handbook. Most tyre manufacturers also supply correct pressure and fitment details for their tyres. Tyre pressure relate to loads, speeds and vehicle handling and the right tyre pressure is vital for even braking, maximum grip and good tyre life
- Inflation pressure should be checked at least once a fortnight when the tyre is cold since there is an increase in pressure when the tyre has warmed up after being run. A reliable pressure gauge should always be used.
- Tyres can deteriorate with age which shows as cracking of the tread and sidewall rubber. Cracking is usually an indication that tyres have been in service an extremely long time.
- If cracking is severe the tyre must be replaced.
- Tyres fitted to caravans and boat trailers which are parked for long periods of time, particularly in coastal regions, will tend to age and crack more quickly than those which are used and run frequently.
Punctures and Repairs
- Repairs to tyres and tubes must be carried out on serious note and should be always entrusted to a specialist.
- All punctured or damaged tyres should be removed from the wheel for internal and external examination to ensure that there is no hidden damage that could cause a later failure
- Tyres should always be re-balanced after a puncture repair
Caravans and car trailers
- Caravan and trailer tyres may need higher inflation pressures than are required for the same tyres on a car.
- It is essential that correct pressure is maintained
- You should never use a tyre on a damaged, distorted, or a modified wheel since this could lead to damage and deflation of tyres and could result in the loss of control of vehicle.
Tubes in tubeless tyres
- Inner- tubes of the correct size can be used with tubeless tyres if they are correctly fitted
- Please remember that by fitting tubes in tubeless tyres, in the event of a puncture, the assembly will behave exactly like a tube tyre – it is likely to lose pressure more rapidly than a tubeless tyre assembly.
- Where tubes for certain low profile tubeless tyres are not available, an alternative size tube should not be fitted.