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Macc Tyres Ltd for car tyres

A Guide to Understanding Tyres, what to look for & what those number mean

This is a guide which will hopefully help you understand more about your tyres, how they work, why your tyres are important and how to look after them and in doing so, getting more out of them.

So when its time to buy new tyres for your vehicle and you don’t know what all the numbers mean,  maybe you don’t even know what size tyres to purchase or even where to find the information about your tyre size - then this friendly guide is here to help you through the process and hopefully let you know what the numbers, terminology and ratings mean. Thus, helping you make the right decision in the purchase of the most important part of your vehicle – the tyres.

 
Tyre Manufacturer
Most tyres will have the Manufacturer of the tyre printed on the side wall along with the model number of the tyre. For example: Bridgestone (Manufacturer) Potenza RE050 (model). Because you car has Bridgestones on it, it does not mean you have to replace them with Bridgestones, your vehicle manufacturer recommends this but a comparable model from another manufacturer will do. In fact different tyres have different qualities from Manufacturer to Manufacturer. One brand of tyre maybe designed to be more hard wearing whereas another brand maybe designed to give better grip.
 
As long as the tyre sizes are matched then the model is purely down to the features you require and the price you can afford.
 
Tyre Sizes, What size do I need?
Tyres Size example with Width, Profile, Wheel size, Load Index and Speed ratingTo find out what size tyre is required for your car the best place to look is on the tyres themselves. Numbers quoted in manuals can be misleading as maybe your car has had aftermarket alloy wheels fitted since it was built, making sizes in the owners handbook irrelevant. So we need to look at the tyres you already have on your car.
 
On the side of the tyre there will be some numbers and letters and these correspond to the size of tyre you require when purchasing new tyres.
 
Above is an image of a common tyres and we have highlighted the sizes so they show up better for the purpose of understanding what these numbers mean.
 
Tyre Width (Shown as 225 (in Red in above image))
This is the width of the tyre, measured in millimetres, sizes range from 135 to 355. Common sizes are 175, 185, 195, 205, 215, 225 and 235.
 
Tyre Profile (Shown as 45 (in Yellow in above image))
This is a percentage of the width of the tyre, so on our example 45 is actually 45% of the tyre width which is really 101.25mm
 
Wheel size or diameter of the inner rim (Shown as 18  (in Green in above image))
This is the size of the wheel which the tyre fits on and is measured in inches and is usually preceded with the letter R.
 
Load index (Shown as 91  (in Blue in above image))
This is the maximum load or weight a tyre can support and the higher the number the greater the load. Smaller cars will have a lighter Load Index than say a 4x4 which is heavier and requires stronger tyres to support its weight.
 
Speed Index (Shown as W (in Purple in above image))
Corresponding to the tyres maximum speed. It is prohibited to fit tyres with a speed index below that recommended by the manufacturer of your vehicle.
 
A list of the most common codes and speeds is below.
 
T – 118mph
H – 130mph
V – 149mph
ZR - >150mph
W – 168mph
Z – 186mph
 
Tyre types – All Weather, Summer, Winter and Run Flat
There are a number of different types of tyre relating to the seasons, All weather, Summer and Winter. In the UK most vehicles are equipped with All weather tyres as although you may not think it our mild climate is suited to using All weather tyres all year round. However All weather tyres are a general compromise as in summer they will not grip the ground as well as a Summer tyre nor will they handle snow or ice as well as a Winter Tyre.
 
Summer tyres offer excellent levels of grip in the dry summer season but do not perform as well as all weather tyres in wet and icy conditions as they are principally designed for the dry the tread pattern does not move water or grip in icy conditions as an All season or Winter tyre
 
Winter tyres have are the opposite to Summer tyres, their tread pattern is designed to move large amounts of water and also to grip the road surface in icy conditions. Winter tyres are especially important in places where rain and snow fall effects the road conditions during the winter months. But in hot weather and dry conditions a Winter tyre will not grip as well as a Summer tyre.
 
* Please note that using Summer tyres in Winter and vice versa will have an impact on the stopping distances of your vehicle under braking.
 
Run Flat tyres do exactly as the name suggests. They are designed to work without air inside, after a puncture for example, but only at reduced speed and for no longer than 120 miles. Some vehicle manufacturers now fit run flat tyres as standard and they work by utilising a reinforced side wall which keeps the tyre rigid during run flat usage. They are designed to be replaced at the first available opportunity and not for prolonged usage once flat. For vehicles where no spare wheel is fitted and run flats have been fitted to the car as standard we always recommend replacement with similar run flat tyres.
 
Tread Pattern and Grip
A good tyre should suit the conditions you are driving in, however this can not always be matched so tyres are mostly designed to be a compromise for all weather uses. There are specialist tyres on the market which will give improved grip in dry conditions, these have a very limited pattern on them and are almost like slick tyres but they do not work well in the wet and may increase stopping distances under wet conditions. The same can be said about tyres which have a deep V-shaped tread designed for wet conditions. These tyres will not work as well in dry conditions and sideways road holding will be decreased.
 
So the tyre you choose should be a compromise giving good levels of grip in both wet and dry conditions.
 
In extreme conditions it maybe prudent to choose a Snow or Ice tyre which has numerous deep grooves aiding grip on slippery surfaces, however this tyre also has less grip if used in dry conditions.
 
Our tyres are listed as All Weather, Summer or Winter tyres. Snow tyres are available on request.
 
Tyre wear
Here at Macc Tyres Ltd we cannot stress how important the tyres on your vehicle are, they are the only part of you vehicle in contact with the road and they are what helps you vehicle stop, corner and accelerate. If they are damaged or badly worn then your vehicles ability to do these things is diminished – This is also why Tyres are part of the MOT test which cars have to under go and a yearly basis.
 
You should regularly check your tyres to make sure that they are within the permissible legal limit for wear, this is currently 1.6mm and tyres falling below this level may incur a fine if stopped and checked by the police. Not only is it illegal, it is also dangerous as the lower the tread on your tyres the less they work as designed especially when it comes to stopping distances. A normal tyre with some wear will stop your car quicker than tyres with near, on or below the legal limit. By a considerable margin – almost twice the distance. Once a tyre is within its legal wear limit it should be replaced at the first available opportunity.
 
Wear however can occur in a number of ways, it doesn’t always happen at a uniform depth right across the tyre. Here are a few scenarios which you might encounter and the solutions to these problems.
 
Both Edges are Worn – This is a sign of under inflation, not enough air. Check you tyre pressures, the correct pressure will be written on the tyre or on the fuel filler flap or in the drivers door jam.
 
Worn in the middle – This is a sign of over inflation, too much air. Check you tyre pressures, the correct pressure will be written on the tyre or on the fuel filler flap or in the drivers door jam.
 
Worn on one side only – Your wheels are incorrectly aligned and your vehicle needs the tracking checking. Take you vehicle to a garage and get the tracking done via laser alignment or better still full suspension geometry setup, which check all the wheels are pointing in the right direction to specifications supplied by the manufacturer. Correct suspension geometry will not only make your car handle better it will prolong tyre life.
 
Tyres Worn unevenly – The wheel is out of balance, or the tracking maybe out. Take you vehicle to a garage and get the tracking done via laser alignment or better still full suspension geometry setup, which check all the wheels are pointing in the right direction to specifications supplied by the manufacturer. Correct suspension geometry will not only make your car handle better it will prolong tyre life.
 
Bald spots or uneven wear – This maybe a symptom of badly balanced wheels or even that the shock absorbers on you car are worn or broken.
 
Incorrectly balanced or damaged wheels – The biggest tell tale sign of a badly balanced wheel is that the car feels like its wobbling at specific speed. Slow down it goes away, speed up it gets worse or goes away. Badly balanced does not mean the tyre fitters have made an error so only refers to new tyres. Perhaps you have lost a balance weight or incurred damage to your wheel. A badly balance wheel should be checked quickly as it may also be the start of one of the problems listed above.
Bridgestone Uniroyal Dunlop Federal Yokohama Nankang Pirelli Falken Avon Maxxis