Car Tyres Explained
So you’re ready to buy new tyres but you’re suddenly hit with a whole range of options and variety!
Which are the right tyres to suit you, your budget, your vehicle, your expectations and your safety?
While there isn’t a definitive answer to the question above – understanding what all the numbers, letters, symbols and tread varieties mean will greatly assist you in make an informed choice for your new tyres.
The first thing to remember when you have new tyres fitted – regardless of the make or style – is that they will undoubtedly make the car ‘feel’ different even if they’re exactly the same type of tyre fitted again! It takes a few miles to settle in to new tyres and to understand the subtle differences in handling and cornering that new tyres provide.
Tyre Size Information
Before you buy tyres online with Hometyre, you’re going to need to find out the size and specification currently fitted to your vehicle.
The ONLY way to get accurate detail is by checking the vehicle itself. Don’t rely on the handbook or on online resources.
Be sure to check both front and rear too as they can often differ in size!
A popular size for passenger cars is, for example:
‘205’ represents the approximate width of the tyre in millimeters
’55’ represents the sidewall height as a percentage of the width of the tyre – 55% of 205mm in this instance.
‘R’ represents the construction type – in this, as in almost all modern tyres, denotes a RADIAL construction
’16’ represents the diameter of the wheel measured in inches.
‘91‘ represents the load index (a reference chart detailing the maximum permissible weight the tyre can safely carry)
‘V’ represents the speed rating – in this instance a tyre with a manufacturers top speed rating of 149mph.
Speed Rating Information
The speed rating (denoted by a letter – ‘V’ in the example above) represents the maximum permissible speed for which the tyre is rated and indicates the speed at which the tyre can carry the load corresponding with its load index
You should replace your tyres with those of the same size, load and speed rating as recommended by the vehicles’ manufacturer.
Increasing the value of both the load and/or speed rating is acceptable practice but it is not recommended that lower value products be fitted.
The tyre should be able to withstand the forces applied to it at the vehicles maximum rated top speed.
There is currently no legal requirement for speed ratings but it is advised to check with your vehicle insurer of any potential issues that may arise when significantly altering specifications.
The load index is a numerical code, which corresponds to the maximum load a tyre can carry at the speed indicated by its speed symbol, under specific service conditions:
Symbols used on our website
PASSENGER CAR TYRES
Tyres marked with this symbol are suitable for passenger car use. They may have varying speed and load ratings. It is not recommended to use these tyres for light commercial vehicle applications
LIGHT COMMERCIAL VEHICLE TYRES
Tyres marked with this symbol may be suitable for use on light commercial vehicles (i.e Ford Transit, Peugeot Boxer, Citroen Berlingo etc) as well as caravans and some motorhome/campervan varieties. These tyres will either be a 6ply or an 8ply construction* and will be denoted by the letter C after the wheel diameter e.g. 195/70R15C
* Tyres are constructed from a series of products. To provide it with its strength and rigidity there are numerous layers to a tyre. These consist of metallic bands that cross one another in an X pattern to give the tyre its radial support, layers of cord running across the tyre from left to right and side wall layers. The ‘plies’ are the combination of all the belts or bands that support the tyre.
Standard car tyres are manufactured with four plies to maintain a balance between structure, road handling, noise emission and comfort. A commercial grade tyre has further plies in order to allow for greater load carrying, longevity and higher pressures.
Tyres marked by this symbol will be appropriate for use on 4×4 type vehicles. Please be aware that 4×4 tyres now come in a multitude of styles including:
AW – ALL WEATHER – These tyres are suitable for year round use and offer good response in all weather conditions
AT – ALL TERRAIN – Are a rugged tyre designed to work both on road as well as provide adequate traction and performance off road.
MT – MUD TERRAIN – have a very aggressive tread pattern and would be unsuitable for regular road use.
HT – HIGHWAY TYRE (ON ROAD BIASED) – A 4×4 tyre designed for road use. It would not be suitable for rugged off road use.
HP – HIGH PERFORMANCE – A high speed on road 4×4 tyre with little or no off road capability
UHP – ULTRA HIGH PERFORMANCE – a very high speed capable tyre suitable for Range Rover Sport, Porsche Cayenne etc
It is not advised to mix tyres on a 4×4 vehicle. You should consult your vehicle owners manual before replacing tyres on your 4×4. Some manufacturers recommend that tyres are fitted only as axle pairs or sets. Selecting All Terrain tyres or a more aggressive pattern for strictly highway use will have a detrimental effect on your fuel economy.
RUN FLAT TYRES
Run flat tyres can only be fitted to vehicles with specific wheels suitable for run flat tyres and with an active tyre pressure monitoring system. Typically found on many BMW models, a run flat tyre will support the weight of the vehicle while fully deflated and allow the owner to continue driving for a limited mileage at a limited speed. the down sides to a run flat tyre are firstly the cost, and secondly that once punctured and used, cannot be safely repaired.
Manufacturers designate run flat type tyres with the following lettering codes: SSR, RSC, ROF, RFT & ZP, for example.
Some motorists have opted to replace their Run Flat tyres with conventional tyres. This is a service we are happy to offer – provided the customer is made aware and accepts that handling differences may occur, the vehicle will not carry a spare and therefore could be stranded in the event of a puncture.
NOTE: It is always recommended that you check with the vehicle manufacturer to ensure compliance with warranty requirements before altering the tyre specifications on your vehicle.
Summer offer year round suitability for use under less extreme weather conditions. At temperatures below 7°C however, these tyres become far less effective than cold weather type tyres.Tread patterns and the use of ‘softer’ rubber provide summer tyres with better handling performance during summer months – improving grip, braking and cornering and wet weather water dispersal. Driving style should be altered when used in cold weather – or your tyres should be replaced with a cold weather tyre option.
COLD WEATHER / WINTER TYRES / ALL SEASON TYRES
Specific winter tyres will be designated as such. All season tyres will often have M+S (mud and snow) marked on the sidewall of the tyre. With the exception of high performance vehicles, most vehicles in the UK would be best fitted with an all season type tyre to cope with the varying weather conditions. All season tyres are designed to handle any type of weather with a fair degree of success.
Cold Weather / winter tyres are a superb product for use between November and April in the UK. Contrary to popular belief, they are not solely intended for use in snow or icy conditions – though they perform incredibly well in these circumstances. The design of a winter tyre, and the composition of the rubber, provides outstanding grip and braking performance in cold, wet weather conditions. A summer tyre, below 7°C will continue to harden. Its winter counterpart will remain flexible and supple and allow the tyre to grip the road firmly.
Some vehicles require tyres that not only provide exceptional road holding, comfort and noise reduction, but are also capable of carrying significant loads or have stronger sidewalls to deal with power delivery and/or braking – particularly during cornering. These tyres are also designed to take a higher inflation pressure.
Reinforced tyres are found on vehicles which are likely to carry above average weights – for example small vans, twin axle caravans, people carriers etc. Reinforced tyres will often be denoted by the letters ‘RF’ or on the sidewall. These should not be confused with Run Flat tyres. It is acceptable to fit extra load or reinforced tyres to a vehicle with standard load tyres fitted but not recommended to downgrade.
OWL – OUTLINE WHITE LETTERING
Typically found on 4×4 tyres, the manufacturer and tyre pattern details are marked in raised white lettering on one sidewall of the tyre. (with the exception of assymetric and directional tyres, these are often reversible to hide the lettering to the inside wall should you prefer
These tyres have been specifically designed and tested to suit the handling and performance characteristics of a BMW car. They can also be fitted to other models.
Designated by the letter N and a corresponding number from 0 to 4, Porsche recommend the use of N rated tyresto be fitted as a set with matching numbers – i.e N2. Each number represents the latest development tyre for that particular model/variety of vehicle. It is not generally recommended to fit these tyres to other vehicles.
Designated by the code ‘ K1’, these tyres have been specifically designed and tested to suit the handling and performance characteristics of Ferrari vehicles. It is not generally recommended to fit these tyres to other vehicles.
Designated by the letters ‘MO’ these tyres have been specifically designed and tested to suit the handling and performance characteristics of Mercedes vehicles. The tyres are suitable for fitment to other vehicles.
Designated by the letter ‘J’, these tyres have been specifically designed and tested to suit the handling and performance charatceristics of Jaguar vehicles. These tyres are suitable for fitment to other vehicles.
Designated by the letters ‘RO‘ and ‘AO‘, These tyres have been specifically designed and tested to suit the handling and performance characteristics of Audi vehicles.
BENTLEY / AUDI FITMENT
Designated by the letter ‘B’, these tyres have been specifically tested and designed to suit the handling and performance characteristics of the Audi S3, S4, TT and the Bentley Continental GT range.These tyres should always be fitted as a set of four and can be fitted to other vehicles.
Designated by the letters ‘MC1′, have been specifically designed for use on MacLaren vehicles only. They should always be fitted as a full set of four.