Tyres are something that many drivers don’t really pay very much attention to, and yet their importance should never be under estimated. Complacency with tyres can kill, and that is no sweeping statement made with the intent to be dramatic, as it simply is the truth.

When we talk of safety concerning tyres, we are not just talking about tread depth, as that would be far too obvious. There are other issues with rubber that are far more sinister, and they are so because the dangers are not nearly so obvious.  This article has been written to advise you on what checks you need to make before you take to the road in your car and what type of things you should be looking for on your tyres to tell you if you are staring at a potential disaster.

Before we get into all that it would be useful to gain a better understanding of a tyre and to learn more about the job it has to do.

When a tyre manufacturer is thinking about designing a tyre they will have to -

• Design a tyre that will comply with the road vehicle legislation applicable to the use of the vehicle to which it is fitted and within the country that it is being used.
  
  
• Design a tyre that is the most appropriate size in relation to the wheel rim.
  
  
• Design a tyre that is capable of being easily inflated and be able to remain so.
  
  
• Design a tyre that is will be appropriate relative to the maximum achievable speed of the vehicle to which it is fitted to and be able to cope with being used at that road speed.
  
  
• Design a tyre that will be constructed in such a manner as to be able it to cope with the type of work the vehicle to which it is fitted will be expected to carry out.
  
  
• Design a tyre that has the ability to disperse water from beneath it and where it is in contact with the road surface upon which it is being driven, and therefore reduce the risk of aquaplaning.
  
  
• Design a tyre that is able to withstand a certain degree of abuse without any adverse effect.
  
  
• Provide details of a recommended pressure that is appropriate for the use of that tyre when fitted upon the vehicle, and that internal air pressure is appropriate according to the weight of that vehicle in order that the contact area of the tyre to the ground is sufficient to provide an acceptable level of adhesion (grip).
  
  
• Provide a comfortable ride for the vehicle occupants without any drop in performance.
  
  
• Have the maximum degree of mileage life as possible, balanced with the required level of grip performance.
  
  
• Be of appropriate external dimensions so as to work in harmony with the dimensions of the vehicle to which it is intended it will be fitted.
  
  

When we talk of tyres we will instantly make an association between that word and the word grip, but what is grip and where does it come from?  A tyre will have a purchase upon the road through the presence of friction between the surface of the tyre where that comes in contact with the road, but that friction will only be present if the tyre is being pressed onto the road, this being achieved by something called down-force.  Down-force on a normal road car comes from nothing more than its own weight, or mass, so the heavier the vehicle the greater the friction between the road and tyre, and you could be forgiven here of thinking this will mean your vehicle will hold the road better or stop in a shorter distance. However, this is not true and to explain that one in full detail it would take another whole chapter, so for the purpose of this article it is sufficient to understand that if your car had no weight then your tyres would have no grip.

We’ve brushed over the subject of tread depth at the top of the page, and it is important that we have a good level of tread on the tyre, as it is the tread pattern that disperses the surface water away from the road under the tyre when we drive in wet conditions. If there were no tread pattern then the water could not be dispersed and a cushion of water would form between the contact surface of the tyre and the road surface is was travelling over.  This causes a loss of grip through a condition known as Aquaplaning, and if there is anyone out there who has experienced this at first hand they will know that is it extremely frightening.  It is therefore important to understand what the legal requirement is concerning the minimum permissible depth of tread will be for your tyres.

The minimum requirement for cars, and goods carrying vehicles with a gross plated weight of 3,500kgs, is 1.6mm in a continuous band around the whole circumference and for at least 75% of the overall width in the centre of the tread area.  However, our advice is that in practical terms, and whilst the above may be legal, the legal depth is still too low, as even at 1.6mm your car will be very susceptible to aquaplaning and really any tyre should be replaced well before it gets to the legal limit.

A good rule of thumb to use when making judgement if it is worth keeping a tyre on your car is that if the tyre looks iffy then it is iffy and should be replaced. As we said, don’t just look at tread, as there are other issues that need to be addressed.  Look out for tears in the rubber, lumps, bumps, splits and cuts, and of course, check the air pressure in each to make sure they conform to the manufacturers specification. If you have any doubt as to whether the tyre is still servicable, scrap it and get another, as it is not worth messing about with something as vital as this.

Actually, if you drive on a tyre that is completely devoid of tread pattern, and if you do so on a dry road, you will have better grip than if you were on a brand new one with loads of tread on it.  However, this would not only be illegal, but of course stupidity, as this would be highly dangerous when it started to rain.

What else is there to know? For a start there is pressure, but not the kind you get from your spouse or partner because you haven’t done something that you were supposed to do. Ask yourself how often you give this a thought, and for those who do give it a thought, how many actually make a physical check to see if the tyres of their vehicle are properly inflated?  Tyre pressures are vital in the Ride Drive on the road survival guide, and the importance of this subject should never be underestimated.

Air pressure within the tyre is what keeps it at the right shape whilst you are driving and what makes it do the job it was designed to perform. If you have a difference of pressure between two tyres fitted to the rear of your car, for example, this will, under the wrong circumstances, cause severe vehicle instability, even if that pressure difference is just a couple of pound per square inch. This is because different pressures within tyres will produce a different rate of what is called a Slip Angle.

Without getting into what may appear as rocket science, a slip angle is basically the rate of creep of a tyre across the road surface when the vehicle it is fitted to is cornering, and when you have a difference across an axle you are in deep trouble.  This is one of the reasons why you should never mix tyres of differing structures on the same axle.

If you do have a disparity in tyre pressures, whilst maybe you are pottering around the town in traffic, you would probably never notice there was anything wrong, and there is a high chance that nothing would go wrong whilst in that environment.  You may not even notice anything untoward on slightly more free-flowing suburban routes, but then get out on the open road, and begin to build up speed, and the next corner you come to could be your last.  A car can actually be quite stable even on the wrong tyre pressures, providing those pressures are the same across a particular axle and do not differ by any great amount to what is recommended. However, the difference from one tyre to its opposite on the same axle only needs to be a small amount to cause instability and loss of control, and same applies of you were to have too wide a difference from to rear.  Differences in pressure between the front and rear pairs can cause a devastating effect on the behaviour of the vehicle, especially if the balance is completely the wrong way around.

You will often here of people discussing tyre blow-outs, mainly because this is something that many will fear will happen to them. A tyre blow-out, to give it a definition, is the sudden and total deflation of a tyre caused through the collapse or failure of its structure. There is a tremendous amount of rubbish talked of when it comes to blow-outs and something that is severely misunderstood amongst the motoring population. Blowouts do not just happen, they are caused, and that cause 99.9% of the time is through negligence, in terms of simple maintenance and regular visual chacks, coupled with a lack of awareness.

As mentioned earlier, the air pressure within a tyre is necessary to maintain the integrity of the profile of that tyre and therefore its structure. If you steadily reduce the air pressure within a tyre you will reach a point, long before it becomes flat, where the tyre walls begin to bulge outward. If that car is driven with the soft tyre, the bulging tyre wall, now less rigid due to lost air pressure, will begin to distort and even ripple as the wheel rotates. This rippling effect causes friction within the rubber, and as you know friction causes heat. All the time a car is being driven along the road with a tyre in this condition that tyre is generating heat within itself and the level of heat will be rising for every metre of distance it is allowed to drive over. Eventually there will come a point when the tyre will have had as much heat as it can tolerate, and when that point comes it will suddenly let go with a bang. If you realise what is going on before you get the final failure point, and you try to put your hand on the tyre just after you have come to a stop, you will burn yourself.  There is a terrific amount of heat generated here and tyres running on a vehicle whilst under inflated have even been known to ignite.

Let us not get carried away here, but instead ask ourselves why the tyre has gone soft in the first place, after all, that is the cause of the problem and the beginning of this chain of events?  The answer is that you have either picked up a nail, or similar, that is stuck into the tyre body and you now have a slow puncture, or it might even be that the pressure has not been checked for so long that the tyre has gradually deflated little by little through age and neglect. It could be that you have been running around for weeks like this, but because you have been the only occupant of the car you have got away with it. Now, when you have got three other people on board and a boot full of luggage, things are very different.

Another contributory factor is age. Have a look at the walls of your tyres. Now have a really good close look. Do you see any signs of a small crazed pattern in the rubber – like a mini crazy paving design? If you can then the walls of the tyre are perished and therefore weakened. Sunshine and salt spray are the biggest culprits when it comes to causing rubber to degenerate and is most common on those vehicles that are used infrequently, and which stand outside. Touring caravans are the most affected in this category, as they are often stood in some outside storage space for eleven months of the year before spending a couple of weeks on the road during the family holiday.  Any sign of deterioration in a tyre then get rid of it.  Keeping substandard tyres is foolish and may cost you or someone else a life.

Another aspect of tyre deterioration you may wish to consider concerns your spare wheel. Where is it carried on your vehicle? Most 4x4’s have them mounted upon the rear-loading door, which is fine providing it is covered over. If it isn’t covered then it will deteriorate and perish very quickly in the light of the sun.  Those mounted beneath the vehicle will not last long either, as they receive all the salt spray and muck that is flung around under the car; coming up from the road wheels, so check them on a regular basis too.

When did you last hit a kerb or pothole, bump up the kerb whilst trying to park or run over a piece of debris on the motorway? When you did that, what damage has it done to the tyre? Sure enough, when you have maybe looked at it to see what sort of condition it is in, the tyre may have appeared to be fine, but that will only be a visual check you have made from the outside.  What damage has the tyre really suffered and how could it affect your safety?

If you have just banged your car up a kerb you may well have caused havoc to the inside of the tyre, and you won’t see what's there unless you take the tyre off the rim. Broken ply-cords and layer separation of the rubber banding is a common symptom of bumping up and down kerbs, but from the outside you will never see it. Then get out on the motorway, and start making progress along the road, then you could find out the hard way that you are in trouble.  The golden rule here is to never ever assume anything, or you could pay dearly.




When you are cleaning your car use this as an occasion to check your tyres for stones or other objects that may have become wedged in the tread grooves.  Harmless enough at first, but these can wriggle and worm their way through the rubber and end up causing a puncture.  If you don’t clean the car often, check for foreign bodies in the tread anyway.  If you find you have one tyre that has gone soft on you, don’t just put air into it to blow it up again, investigate the reason as to why it has gone soft, as probably there will be a nail or screw stuck through it.

Another thing to do, and this concerns mainly the front wheels, put the flat of your hand across the tread area and with light pressure only, and run your hand around the circumference of the tyre. Do this backwards and forwards.  What you are feeling for is whether the tread has become stepped or feathered.  To explain this further, if you imagine stroking a cat or a dog, and you try to do so by running your hand from its tail towards its head, you will notice it feels totally different to when stroking the animal in the more normal direction.

If there is a difference to the feel of your tyre tread according to the direction in which you are running your hand around it then you need to investigate this further.  Tyres tell us a lot about the state of health of a car, and a feathered tread can be a symptom of defective or worn shock absorbers and or wheel bearings, steering joints, wheel misalignment or incorrect wheel balancing.  It can even give you a clue as to whether your brakes are binding (failing to release properly). Check across the tread area to see if there is a difference in tread depth from one side of the tyre to the other, as this will be another symptom of a wheel alignment, or tracking fault.  A tyre that is scrubbing on the outside edge will tell you that the wheels are toeing too far inward, as in each will be steering slightly toward the other.  Scrubbing of tread on the inside edge indicates the wheels are toeing too far outward and so effectively trying to steer away from one another.

The front wheels, and even the rear wheels in certain cases, will never be set to run completely parallel with each other.  Front wheel drive vehicles will have their front wheels set with a small amount of toe-in, whilst rear wheel drive cars will have the opposite.  This is set to compensate for the forces that are acting upon the wheel assemblies whilst the vehicle is being driven, so that when in motion the wheels then do line up.

Excessive wear around the centre of the tread area is a symptom of that tyre being driven upon whilst over inflated, whereas excessive wear to the area of both shoulders, as compared to the centre, indicates use in an under inflated condition.

Lastly, when you take your vehicle to a tyre centre the staff should have been trained to a high standard, and therefore should be able to advise you as to the most appropriate tyre to choose for your car.  However, it doesn’t hurt for you to know a thing or two about tyres before you attend, as being better informed will give you more confidence in making your choice.  Every tyre has a ply and speed rating, and information concerning this will be given on the wall of the tyre.  Whilst the maximum speed limit for UK roads is 70mph, you should be fitting tyres to a 140mph car that are capable of withstanding that sort of speed, so as to be compatible with the vehicle type.

When dealing with top range cars, particularly sports models, many have tyres that have a tread that is known as Directional Tread.  That is to say the tyre has to be fitted to a wheel that has the same rotational direction as that intended to serve by the tyre.  In other words, you will have left and right-handed tyres, and to put a right hand tyre on the left side of a car will not be a good situation.  Your tyre centre staff should know all of this, but it is always best to keep an eye on what is going on.