Here you can get Checking for wheel and tyre damage, Tyre sizes and markings.
Tyres are put under tremendous strains when a car is being driven. There are only four relatively small areas of tyre tread in touch with the road. They carry the car’s total weight, and transmit to the road the power that drives and accelerates it over the various changes of surface and gradient encountered. They must also transmit the forces generated by braking and cornering.
Because they’re in constant contact with surfaces that are frequently abrasive, damaged and even broken, tyres are more liable to wear and physical damage than the other car component. For safety’s sake, keep a daily check on them – and on the wheels that carry them. Make it at least once a fortnight, and also before any long or high-speed journeys. Badly worn or damaged tyres are both illegal and potentially lethal: they will cost you your licence – or maybe your life.
It is better to seem over the tyres and wheels while they’re on the car than to not inspect them in the least. except for a thorough examination of the within walls, the wheels should be began about once a year (See Checking, removing and refitting road wheels ).
Inspecting tyre treads and sidewalls
The tread is that the obvious place to start looking for tyre damage. Begin by inspecting carefully the entire circumference for abnormal wear and flaws within the pattern. Abnormal widening of the grooves , or the spaces between tread blocks, usually means the tyres are ageing. If a series of cracks is clear , replace the tyre – even though there may still be 1-3 mm of tread left. Pay special attention to the tiny slots and cuts – known as ‘sipes’. search for embedded fragments of sharp flint and stones, or the nails and tacks that are the usual cause of punctures and can cause internal damage.
That sort of debris are often prised out with a screwdriver blade. But removing it may leave the tyre with a slow puncture. Check for loss of pressure , and if it occurs have a tyre-repair shop take the tyre off the rim, inspect it, and make a permanent repair. Look also for ‘flats’ within the tread, worn perhaps by severe emergency braking – when the tyre of a locked wheel slides on the road, wearing off the rubber and generating tons of heat. Abnormally severe wear at the tread shoulders or uneven tread wear are warning signs that ought to never be ignored.
They could be the results of more fundamental problems perhaps within the tracking or suspension and will soon cause failure at speed (See Avoiding tyre wear ). Bulges within the sidewalls are signs of carcass damage. Long before cords are showing through, these tyres are unsafe at speed. Sometimes the damage might not be visible, so if you’ve got suspicions – perhaps after hitting a kerb – but cannot see any exterior evidence, ask a professional tyre fitter to remove the suspect tyre and examine it. Often, fractures are visible inside before they become obvious outside. Any break within the carcass construction means replacing the tyre. It can’t be repaired safely.
Checking the tread depth
Tyres with treads of less than 1 mm deep are illegal in Britain. The treads must be a minimum of 1 mm deep over 75 per cent of their tread width all around the tyre, and there must be evidence of some tread on the rest..However, most experts think this is often not enough, which it’s unwise to drive on tyres in such a worn state.
Many other countries including most European and North American states – demand that the minimum tread depth should be present across the complete width of the tread in touch with the road. European regulations are likely to return into force in Britain under EEC regulations. A minimum of 1.5 mm is common, and a couple of mm is strongly recommended within the interests of safety. In practice, it’s sensible to require a tread depth of two mm because the stage at which tyres should be renewed. As soon as tyres begin to point out signs of wear and tear, make frequent checks. Even with new tyres, regular. checks also can reveal unusual wear patterns, which point to other problems.
You can make an easy check on tyre-tread depths with an implement like a small screwdriver, which features a narrow, straight blade which will fit into the grooves between treads or tread blocks; you also need a millimetre rule or measure. Put the screwdriver blade into the groove at right-angles to the tread surface, then use your thumbnail to mark the surface level on the blade. Taking care to not move your thumb, measure off the depth on your ruler. Inexpensive tread-depth gauges also are available, which make checking even easier, and more precise. confirm that the probe is extended fully, then insert the tip into the groove and press down. The tread depth are often read off on the gauge scale.
Check all round each tyre. Move the car slightly to include the sections of tyre on which the car was standing. Some tyres are made with built-in tread-depth warning markers usually bars running across the within of the grooves. When the tops of the bars become flush with the tread, the tread depth is nearly at its legal limit and therefore the tyre should be renewed.
Tyre sizes and markings
Most new tyres are radial-ply tyres. All reputable new radials are marked with the size and speed rating , cross-plies with the size only. Tyres without such markings are best avoided. Generally, tyres have two size markings – the width of the tyre and therefore the diameter of the wheel rim. the size could also be given in inches or millimetres or a mix of both; sizes solely in inches are on cross-ply tyres.
A tyre marked 6.40-10, for instance , is 6.4 in. wide on a ten in. diameter wheel, one marked 135-355 is 135 mm wide on a 355 mm wheel, and one marked 165-15 is 165 mm wide on a 15 in. wheel. Letters interposed between the sizes are speed ratings, for instance 155SR10. For radial-ply tyres speed ratings are: SR up to 113 mph , HR up to 130mph, and VR over 130mph. On newer tyres with EEC approved markings, there’s just one letter interposed – R for radial – and therefore the speed rating letter is separate. variety beside it, like 155R10 76 S, is that the load index for the maximum tyre load in kilograms; 76, for instance , indicates a 400 kg load.