The majority of us understand the basics of tyre safety, so why do we wait until our MOT to be told we need new tyres? According to the Driver and Vehicle Standards Agency (DVSA), between April 2015 and March 2016, over 2 million class 3 and 4 vehicles (cars and light vans up to 3,000 kg) failed their MOT due to defective tyres.

Dangerous and illegal tyres account for one in four MOT failures.

As the only point of contact with the road, it is important to understand how the condition of your tyres can affect your vehicles safety and its performance.

Having over or under inflated tyres, even by one bar, can reduce a cars fuel efficiency and it is estimated that British motorists may be unnecessarily spending up to £600 million on fuel because of incorrect tyre pressures. In addition to reduced fuel efficiency, having incorrect tyre pressure may reduce the longevity of your tyres. It can also affect your cars road handling, increase the vehicles stopping distance and consequentially, the likelihood of being involved in a road traffic accident is greater.

Stopping distances:

The distance your vehicle takes to stop will depend on your attention, weather conditions, the road surface, your vehicle and the condition of its tyres. Typical stopping distances, as published by the Highway Code are as follows:

Car Stopping Distance

In wet weather, stopping distances are doubled, in icy conditions they are multiplied by 10. If your tyres are worn to their legal limit of 1.6mm, your vehicles stopping distance can be increased by as much as 60%.

Shockingly, statistics compiled by The Department for Transport (2014) reveal that, where vehicle defects were a contributory factor to reported fatal road accidents, 56% were due to illegal, defective or under inflated tyres.

If these statistics alone aren’t enough to get you running outside to check your tyres, then we don’t know what is but, if you’re unsure of what to check for, we’ve devised this useful tyre safety guide, so you don’t have to become statistic!

Tyre Tread Depth:

The legal requirement for a tyre tread depth is a minimum of 1.6mm across the central three-quarters of the tyre. The tread must meet this requirement around the tyres’ entire circumference.

Checking your tyre tread depth is a task you should perform regularly. Follow our simple techniques for a quick and pain free solution:

Tyre Tread Wear Indicators:

Most tyre manufacturers now produce tyres with tread wear indicators. These are small, raised ‘nodes’ that are evenly spaced around the circumference of the tyre, within the main tread grooves. If the tyre has worn to a point that the ‘node’ is flush with the outer tread, it means the tyre is below its legal limit and needs replacing.

car tyre tread wear indicators

The 20p Test:

As you can imagine, this test involves using a 20p coin. Simply place the coin in the main tread grooves of the tyre. If the tyre is above the legal limit, the outer band of the 20p will be hidden from view, within the tread of the tyre. If the outer band is visible, the tread depth may be illegal and the tyre may need replacing. It is important to check several locations on each tyre as they can wear unevenly, particularly if the pressure is incorrect.

car tyre 20p test

Source: https://www.tyresafe.org/tyre-safety/tread-depth/

Buy A Gadget:

Tyre depth gauges offer a quick and simple method of checking the thread depth of your tyres. There are variations in price depending on the sophistication of the model you choose. A manual gauge can be picked-up for under £1 or, if you’re a gadget type of person, a digital gauge (many include a tyre pressure checker) can set you back about £10. Either device will give you a good indication as to how legal the tread depth is on your tyres.

Tread Pattern Wear:

How the tread pattern of your tyre is wearing is a good indication as to the overall health of your vehicles suspension components, the alignment of your wheels and if the tyres are under or over inflated.

Abnormal tyre wear can occur for a number of different reasons, below are examples of the most common problems to look out for:

1. Underinflated tyres:

Tyres with insufficient air will wear more quickly on the outer edges compared to the central area of the tyre. Under inflation causes a dip in the centre of the tyre meaning the outer edge, and potentially the wheel rim, are more susceptible to damage.

2. Overinflated Tyres:

The centre of the tyre tread will appear more worn if your tyres have too much air. Overinflating causes the tyre to bulge in the middle, meaning there is less surface area in contact with the road, which not only makes for an uncomfortable ride but also reduces grip.

You should check your tyre pressures regularly to ensure they meet the manufacturers guidelines. The correct tyre pressures for your car can be found in your vehicle handbook, inside the fuel filler cap or on the driver’s door sill. Alternatively, TyreSafe have devised a useful tyre pressure checker on their website, all you need is your car make and model. It’s also worth noting, when shifting heavy loads, your tyre pressure will need increasing, recommended settings can be found in your vehicle handbook.

3. Camber and Toe:

These are the angles of the wheels; camber is the lean of the wheel away from the vehicle when viewed from the front, toe is the direction the tyres point relative to the centre of the vehicle. If the tyres are excessively worn on the outer edge, positive camber and/or toe-in are the likely suspects. If the tread is worn on the inside edge of the tyre then negative camber and/or toe-out is the issue. With toe-in and toe-out you may also feel a feathered effect when running your hand along the tread.

If you suspect your car is suffering from a camber and/or toe problem, don’t panic, a simple wheel alignment by a reputable garage should fix the issue. Misalignment can happen when we accidently hit a kerb, drive through a pothole, or it could be the result of worn suspension components, whatever the reason, it’s definitely worth getting it checked out.

4. Balance:

If you notice cups or dips around the edge of the tread, or if you experience a tyre wobble or vibration when driving over 40-50 mph, one or more of your tyres could be out of balance with the others.

Wheel balancing is a straightforward job for any reputable garage. The technician will place small weights at specific points around the edge of the wheel to ensure that the weight of the wheel and tyre is even around the axis. If a re-balance doesn’t fix the issue, then the problem could be more serious, such as weakened struts or shock-absorbers, your garage will be able to advise.

Condition:

It is a common misconception that if you drive infrequently or cover little mileage, your tyres will not deteriorate. Tyres age and therefore, it is important to visually check your tyres on a regular basis. Remember to move your car either forwards or backwards so the entire tyre can be inspected. Outdoor temperature, your driving style, the speed at which you travel and your load can all affect the condition of your tyres. Here’s what to look out for:

1. Debris:

Stones and grit can be troublesome for tyres. If debris becomes embedded in the tread, it can work its way into the casing of the tyre and result in a puncture. Remove all debris and if you suspect any damage, no matter how small, it’s advisable to get the tyre checked by a specialist.

2. Lumps and Bulges:

Potholes, speed bumps and kerbs can damage the structural integrity of the tyre sidewall. If the sidewall becomes weakened, air leaks from inside the tyre through to the carcass creating a visible lump or bulge. If you find a lump or bulge in your tyre sidewall, it is unlikely that it will be repairable so expect to have to replace the tyre.

3. Tears, Cuts and Cracks:

A tear, cut or crack in your tyre doesn’t necessarily mean it has to be replaced. In some cases, depending on the severity, a repair can be carried out. This type of damage is often caused by that pesky debris, or it may be just plain old age weakening the rubber. When inspecting for tears, cuts and cracks make sure to check between the tread grooves. If you discover nylon cords poking through any damage on the tyre, the internal structure may have been compromised so DO NOT drive the vehicle without first changing the tyre.

The lifespan of a tyre cannot be determined by a single factor. Heat, storage and the conditions of use all influence how tyres age but if your tyres are approaching five years old, it’s advisable to keep close eye on their condition and consider replacing them. To identify the date your tyre was manufactured, and establish its age, a four-digit code is imprinted on the tyre sidewall. Sometimes proceeded by ‘DOT’, the first two digits of the date stamp represent the week of manufacture and the second two digits signify the year of production. The tyre below was made in the 6th week of 2013.

Source: https://aston1936.com/2016/01/15/inspecting-the-tires-on-an-aston-martin-db9

Signs of damage to a tyre, such as lumps, bulges, tears, cuts or cracks can be extremely dangerous and may put you at risk from a tyre blowout. If you are in any doubt contact a tyre specialist.

Tyre Size:

The size of your tyres must be in accordance to your vehicle manufacturers handbook. The handbook may specify a different size for the front and rear, but tyres fitted to the same axel must be of the same size. Once you know the correct tyre size for your vehicle, check this matches the size currently fitted, the tyre size will be printed on the sidewall of your tyres.

car tyre wall information

Width:

This is displayed in millimetres so for our tyre above marked 195, the measurement across the tread from sidewall to sidewall will be 195mm.

Profile:

Also known as the aspect ratio, this is the height of the tyre sidewall, expressed as a percentage of the tyre width. For our tyre above its 55, meaning that the profile height of the tyre is 55% of its width.

Rim Diameter:

These two digits represent the size of the wheel rim that a tyre can be fitted to. For our example, the rim diameter is 16, so this tyre will fit on a 16-inch wheel rim.

Load Index:

This number indicates a tyres maximum weight capability. A load index of 87, as in our example, specifies a maximum load weight of 545kg. Check the table below for your tyres maximum weight capability.

Load Index Load (kg)   Load Index Load (kg)   Load Index Load (kg)
62 265 84 500 106 950
63 272 85 515 107 975
64 280 86 530 108 1000
65 290 87 545 109 1030
66 300 88 560 110 1060
67 307 89 580 111 1090
68 315 90 600 112 1120
69 325 91 615 113 1150
70 335 92 630 114 1180
71 345 93 650 115 1215
72 355 94 670 116 1250
73 365 95 690 117 1285
74 375 96 710 118 1320
75 387 97 730 119 1360
76 400 98 750 120 1400
77 412 99 775 121 1450
78 425 100 800 122 1500
79 437 101 825 123 1550
80 450 102 850 124 1600
81 462 103 875 125 1650
82 475 104 900 126 1700
83 487 105 925

Tyre Speed Rating:

A series of tests measure a tyres capability to operate at a set speed over a prolonged period of time. The speed rating of a tyre is represented by a letter, in our example it is a ‘V’, which indicates our tyre can maintain a maximum speed of 149mph. The table below provides the maximum speed your tyre is capable of maintaining:

Speed Rating Miles/hour (mph) Kilometers/hour (kph)
N 87 140
P 93 150
Q 99 160
R 106 170
S 112 180
T 118 190
U 124 200
H 130 210
V 149 240
Z 150+ 240+
W 168 270
Y 186 300

Fitting an incorrect tyre size can result in an MOT failure.

Construction:

Legally, tyres of the same construction must be fitted to the same axel. There are two basic types of tyre construction; radial and cross-ply, each has its own unique set of characteristics:

1. Radial:

Invented by Michelin in 1946, the construction of a radial tyre allows the tread and sidewall to act independently, giving flexibility, strength and greater control over the direction of travel. The majority of tyres manufactured today are of radial construction.

2. Cross-Ply:

Generally, cross-ply tyres are only used on vehicles that work in extreme terrain as they have a rigid sidewall construction which protects against sidewall punctures from tree stumps or sharp rocks. A cross-ply tyre has a relatively low speed rating, meaning if you are travelling at motorway speeds over a period of time, you could experience a blow-out.

The construction of your tyres can be determined by the printing on the sidewall. If there is an ‘R’ between the profile and rim diameter (as shown in the diagram above), the tyre will be of radial construction, if there is a – between these two elements, the tyre will be of cross-ply construction.

The MOT:

During an MOT, tyres and wheels will be inspected to check for the type of structure, the overall condition of the tyre, the size and the tread – pattern, breadth and depth. Spare wheels and tyres are not checked during the MOT process unless they are fitted to the vehicle. If, at the time of MOT, for some reason you have a ‘temporary use’ wheel fitted to your vehicle, the MOT test will be failed.

Vehicles first used on or after 1st January 2012 will also have their Tyre Pressure Monitoring System (TPMS) checked during the MOT to make sure it is still working. Your vehicle will fail its MOT if a TPMS warning light is displayed on the dashboard at the time of testing.

Tyre Pressure Monitoring System:

TPMS tyre pressure monitoring system

The TPMS is a safety feature that automatically measures the pressure and, in some cases, the temperature of your tyres. There are two types of TPMS:

Indirect TPMS:

This type does not have physical air pressure sensors but detects low tyre pressure through the wheel speed sensors of the vehicles Anti-lock Braking System. When a tyre is low on pressure, its rotational speed increases and it is this difference between the rotational speed of each individual tyre that the indirect TPMS system recognises. If your tyres are all equally deflated, the indirect TPMS will not detect any difference between each tyres rate of revolution so you will not be alerted to an under-inflation problem. An indirect TPMS also requires the vehicle to be driven before an issue can be detected.

Direct TPMS:

Within each tyre is a pressure monitoring sensor that is able to detect any changes in individual tyre pressure levels. A direct TPMS may also provide tyre temperature readings. This type of system tends to be more accurate than an indirect TPMS as it collects data straight from the tyre valves. Cars manufactured after 2014 will generally have a direct TPMS fitted.

The Legal Stuff:

If caught with defective tyres you could face a fine of up to £2,500 per tyre. If all four tyres contravene regulations, you could be slapped with an enormous £10,000 bill. You will also be rewarded for your defective tyres with 3 penalty points that will stay on your driving record for 4 years from the date of offence.

Now you know how important tyre safety is, please don’t leave it to chance or until your MOT, get out there and get checking.