Top 10 Questions About Tyres

• How do I know when my tyres need replaced?

  If you notice that your car is not performing as well in wet weather, that it doesn’t handle or grip, or takes longer to stop when you brake then your tyres may need replacing.

  As tyre wear is a gradual process it can be hard to tell when your tyre needs changing which is why we recommend monthly tyre checks.

• How do I measure tread depth?

  A quick and simple way to check your tread depth is with a 20p coin. Insert the coin into the tread grooves at three separate places on your tyre.

  If you can see the outer rim of the 20p piece, then this could indicate that your tread is close to or below the legal minimum of 1.6mm and you should visit us to have your tyres checked. You should perform a quick visual inspection of the general condition of your tyres too.

  Another way to check tread wear is the Tread Wear Indicators (TWIs) which many manufacturers now include within the tyre grooves. When the TWI is worn down, it indicates that the tread may be nearing the legal limit.

• How important is tyre pressure?

  The correct tyre pressure is very important; it helps your tyres last longer, provides a smooth, more comfortable ride and makes your fuel go that bit further, so the right tyre pressure helps you save money as well as improving safety.

  It also reduces carbon dioxide emissions which protects the environment. Did you know that 37% of cars run on tyres which are dangerously under-inflated? The correct inflation for these vehicles would save £440 million per year!

• Should I repair a puncture?

  Punctures can be repaired, providing they meet with British Standard AU159. Tyres can only be repaired in the central area of the tyre (the part marked ‘T’) – the sidewalls are not repairable, and for V rated tyres and above, only one repair is allowed.

  However, before any repair is carried out, the tyre must be fully inspected for any signs of internal damage which could cause tyre failure.

• Can I replace only one tyre at a time?

  It’s best to replace all four tyres at the same time; however this isn’t always necessary if only one tyre is worn or damaged.

  However it can be beneficial replacing two tyres at a time and as a pair, either the front two tyres or the rear two tyres, for optimum handling and grip on each axle.

  All new tyres we supply are balanced when fitted to maximise tyre life, fuel economy and for a smoother ride.

• What are Runflat tyres and how do I know if my tyre is one?

  RunFlat tyres are specially designed to allow you to drive for a short distance with a puncture, even when the tyre is completely flat.

  This is a temporary, emergency measure allowing the driver to get to a safe place to repair or replace the tyre. RunFlat tyres should not be driven above 30mph and for no longer than 50 miles.

  Manufacturers include markings on the tyre tread to identify it as a RunFlat tyre; these differ from one tyre manufacturer to another. Common RunFlat markings include:

  SSR – Continental’s Self Supporting Runflat Tyres (SSR)

  ZP – Michelin’s Zero Pressure Self Supporting Runflat Tyres (SSTs)

  Euforia @ (RSC) – Pirelli Run on Flat System Component (RSC)

  RFT – Bridgestone Run Flat Technology (RFT)

  RSC/RunOnFlat – Dunlop Run Flat System Component (RSC)

  RSC/RunOnFlat – Goodyear Run on Flat System Component (RSC)

  ROF – EMT: Goodyear RunOnFlat Extended Mobility Technology (ROF or EMT)

• Can Runflat tyres be repaired?

  It is not recommend that RunFlat tyres be repaired after running in a deflated condition as the structural integrity of the tyre could be compromised which could lead to tyre failure.

• Should I fit winter tyres?

  Winters tyres are specially designed to perform in wet, icy weather and very low temperatures, as well as snowy conditions. They contain a higher percentage of rubber than standard tyres to ensure they maintain grip in low temperatures.

  More motorists are opting to fit winter tyres, especially after the severe winters we have experienced in the UK over the last few years.

  Winter tyres could be a valuable asset if you live in a remote location which is hit with severe winter weather or if you do a lot of driving.

  However it is important to remember that regular tyre tread, pressure and general condition checks are essential for safety when driving, whatever tyres you have fitted.

• What do the markings on my tyre sidewall mean?

  The sides of your tyres are marked with a code which identifies your tyre size. Here’s a simple guide to help you identify the right tyres for your vehicle.

  1. This is the tyre manufacturer or brand name, e.g. Bridgestone, Pirelli, Michelin etc.
  2. This is your tyre size – you need to take a note of this to make sure you get the correct size of tyre to fit your vehicle. 215 is the width in millimetres of the tyre’s cross-section.55 is the ‘aspect ratio’ – the ratio of the sidewall height to the tyre’s cross-section width.R stands for radial-ply construction (nearly all tyres are of radial-ply construction).7 stands for the diameter (in inches) of the wheel that the tyre is designed to fit.
  3. ’96’ is the load index which corresponds to the maximum load a tyre can carry at full speed (indicated by its speed rating – below).To find out your load index, locate the number on the sidewall of your tyres and refer to the load index table at National.co.uk
  4. ‘W’ is the speed rating which indicates the maximum speed for the tyre when the vehicle is at full load.Generally, maximum tyre speed is rated in alphabetical order. However, W and Y rated tyres are a special case as they can operate at higher maximum speeds than older Z rated tyres.It is therefore safe to replace your current Z rated tyres with W or Y rated tyres.
     To find out your speed rating, locate the letter on the sidewall of your tyres and refer to the speed index table on our tyre sidewall pages.Being able to identify the tyre size, load index and speed rating allows you to choose the correct tyre for your vehicle.

  Additional Markings Tyres have a number of additional markings, including dot codes and also fitment codes.
  
  Dot Codes and Tyre Age
  Each tyre carries a DOT code comprising of 11 or 12 letters and numbers.

  The last four digits identify the age of the tyre, e.g. ‘0102’ shows that the tyre was manufactured in the first week of 2002.

  Date of manufacture is important because as tyres get older they deteriorate – even if they have been hardly used. For example, vintage cars or caravans which are stored for long periods and not driven regularly could deteriorate over time.

  When this happens the tyres need to be replaced. If you are unsure, ask for your free tyre check.

  Fitment Codes are stamped on the tyre to help identify any special features making it better suited for certain driving styles or vehicles, e.g. if your tyre is stamped with ‘MS’ this means that it is suitable for mud and snow conditions.

  See the list below for common fitment codes and an explanation of what they mean:

  • RE = Reinforced
  • RF = Run Flat
  • XL = Extra Load
  • WW = White Wall
  • OW = Outline White Lettering
  • MS = Mud and Snow
  • AS = Asymmetric
  • NO = Porsche Fitment
  • N1 = Porsche Fitment
  • N2 = Porsche Fitment
  • N3 = Porsche Fitment
  • C1 = Chrysler Fitment
  • K1 = Ferrari Fitment
  • B = Audi/Bentley/Continental
  • GT Fitment G1 = Various Fitment
  • A = Renault Espace 4 Fitment
  • * = BMW Fitment
  • MO = Mercedes Fitment
  • J = Jaguar Fitment
  • 6PR = 6 Ply
  • 8PR = 8 Ply
  • 10PR = 10 Ply

• Why upsize tyres?

  Changing or upsizing your tyres is one of the simplest ways to upgrade the performance of your vehicle as well as improve the aesthetics.

  While the manufacturer selects the correct tyre for your vehicle, the decision can be a compromise between performance, noise and comfort. Therefore upsizing your tyres can provide the following benefits:

  Improved response to change in direction

  Greater contact area with the ground for a smoother ride

  Improved traction

  Better control and handling

  A sleeker, more modern appearance