Tyres are the contact point between the engine and the road and have a considerable significance with respect to safety. Car tyres can be quite expensive, making it tempting to save on them. Making compromises in this area, you endanger yourself and others. With a few tips and tricks, costs for tyres can be kept within limits. Read in this guide how to drive economically and safely.
The wheel of a family car consists of the wheel rim and the tyre. Since 2014 a pressure sensor is compulsory in all new cars. Inner tubes are nowadays no longer used in normal car tyres, with the exception of tyres for trucks and agricultural vehicles.
The tyre consists of an internal steel mesh and a mantle of rubber. The steel mesh is called “carcass”, giving the tyre its strength. The mantle, securely connected to the carcass ensures the airtightness of the tyre. On its sidewall, the rubber is sufficiently thick to protect the carcass from penetrating moisture. On its tread, the rubber is considerably thicker. The structure of this thick rubber layer, the so-called profile ensures the tyre’s road adhesion.
The task of the profile
The stronger the profile’s structure, the larger the road contact surface. Due to the car’s weight and the rolling movement, the tyre is under constant pressure, slightly widening the tread. With the increased contact surface the tyre adhesion increases as well as the rolling resistance, leading to higher fuel consumption and an uncomfortable driving sensation with stronger vibrations. Reversely, a car drives more smoothly when the profile is smoother as well. Therefore, winter tyres have a considerably stronger profile than summer tyres. The strongest profiles can be found on off-road tyres. These are very uncomfortable on the road and wear quickly.
Wear limit of car tyres
A tyre is no longer fit for traffic with a profile of less than 1.6 mm. If this limit is observed, it is no longer an “o.k. situation”. Instead, the tyre must be changed immediately. Starting at this profile depth the tyre’s condition is no longer safe for traffic. The AA strongly recommends not using the tyre when the profile depth has reached 4 mm. On used tyres, the profile must be deeper and the tyres should not exceed a certain age. Although there is no legal age limit, the AA recommends a maximum age of 6 years.
Checking the wear limit of car tyres
Tyre wear occurs in two ways:
– Abrasion of the rubber layer and the profile
– Age too advanced
Abrasion of the rubber layer can be checked visually as well as with a measuring device. If the sidewall of the tyre shows fissures or the carcass is sticking out at certain points, the tyre is no longer safe for traffic. Porous material can cause water to penetrate the carcass, causing it to corrode. A weakened tyre will sooner or later burst, causing potentially dangerous situations. The depth of the profile is measured with a tyre tread depth gauge or alternatively with a 1-euro coin, its brass outer rim being exactly 3 mm wide. In this way, the tyre’s fitness for traffic can be more or less determined.
Measurements are taken exactly at the tread’s centre. Please note: When measuring the profile depth in the centre of the tyre, the edges must be checked as well. If the tyre becomes shiny at the centre or at the exterior, the tyres are no longer safe for traffic. This is either a sign of incorrect operation or damage to the car. The tyre should be checked for damage and foreign elements.
The maximum age of the tyre can be established by its DOT number. This 4-digit number indicates the calendar week and the year of production of the tyre. The DOT number “1915” signifies correspondingly “made in the 19th calendar week of 2015”.
The purchase of a tread depth gauge is strongly recommended. This useful tool is cheaply available at the dealers.
How to use car tyres properly
Correct use of the tyre implies:
– correct mounting.
– correct inflation.
– careful treatment.
One frequent mistake when mounting a tyre is not considering its running direction. The tyre should always be mounted in such a way that it rolls in the right direction when driving forward. Ignoring this causes premature tyre wear and higher fuel consumption. Traffic safety is compromised as well. The correct running direction is indicated on the sidewall of the tyre. The arrow is often somewhat stylised; therefore look closely.
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Inflation of the tyre has a direct effect on fuel consumption, traffic safety and wear. An insufficiently inflated tyre causes high wear and fuel consumption and results in an unsteady driving sensation and instability. Slipping and swerving are more likely in case of insufficient internal pressure. Ultimately, in a tyre in need of air, the carcass is excessively kneaded, possibly causing internal damage and overheating of the tyre. In the worst case, a tyre fire could occur.
Too strong inflation of the tyre makes driving difficult as well. The car skids more easily due to insufficient adhesion. If the car has no automatic pressure control, a two-weekly pressure check is recommended, whether or not the car is often used. Car tyres also lose pressure when standing too long.
The correct air pressure is indicated somewhere in the car. Typical places are the inside of the tank cap or the inner frame of the doors. Furthermore, it can be checked in the car manual. Many petrol stations offer “tyre gas” in addition to the normal air pressure for filling the tyres. However, this is mainly expensive and its utility hasn’t been proven.
The strain limit of the car tyres should not be exceeded. “Screeching tyres” through accelerating too quickly or braking too abruptly cause untimely wear. Since the general introduction of ABS the risk of flat spots on the treads is negligible. Nevertheless, strong positive and negative acceleration can cause wear and unnecessarily high fuel consumption even with the modern assist systems.
The biggest mistake in tyre maintenance is their storage.
Ideally, tyres are stored with a service provider, generally tyre retailers and connected garages. This saves work, space and doesn’t cost much.
Saving money at tyre purchase
Basically, there is nothing against equipping a car with used tyres. As long as the age and the profile depth are within proper limits and the tyre is undamaged, there is nothing to fear.
Re-treaded car tyres are offered as a possible alternative for used tyres. A new profile is vulcanised onto the old profile layer. Modern procedures make this option very safe. For normal family cars, re-treaded tyres can be used without any danger. On sports cars, this option should not be used, as re-treaded tyres have limited speed.
An expensive branded tyre does not automatically mean a better tyre. Therefore it is recommended to consult the available product testing information prior to tyre purchase. Cheap no-name tyres are often just as good as expensive branded tyres.
Tyres wear quicker on the front axle than on the rear axle. This is due to the fact that the car is heavier at the front because of the engine. For a very long time, it was assumed to be better to change the tyres per axle on occasion of changing from summer to winter tyres in order to ensure simultaneous wear for more economic use. This has turned out not to be entirely true:
The “more important” tyres are on the rear axle. They keep the car in its track and prevent swerving sideways. Therefore changing to “better” tyres should always first occur at the rear. Car tyres on the front axle should be used up to their wear limit. Then, the rear tyres are moved up front and the rear axle is equipped with new tyres. This is a lot more economical as well as cheaper. It doesn’t matter if profiles don’t exactly match in depth. In this respect, a car can have different car tyres per axle as long as there is no mixing of seasons. Mixed summer and winter tyres are not allowed.
Foto: ssuaphotos, Ivan Baranov, Joshua Resnick, Nor Gal, Corepics VOF, red mango, 24Novembers, Pakpoom Phummee, Patrick Thomas, mookjera, chartphoto, AWesleyFloyd / shutterstock.com