The situational winter tire obligation is still in place until April 15; those who don’t run into winter driving conditions can change their tires to summer tires anytime. Or change them yourself if the stored tires are still good. Here we explain what you have to bear in mind.
It looks so simple, but you can make many mistakes when changing tires, which can lead to problems, warns the expert organization GTÜ. The correct torque and sequence are crucial. And under no circumstances should you spray Caramba, WD40 or something like that into the thread. But in detail:
Five steps to a successful wheel change
Check 1: Once the winter wheels have been removed, you should inspect the summer wheels and the threads and drives of the wheel bolts or nuts for any damage. Does everything look good? Then mounting can begin.
One note beforehand: Never grease the threads of bolts or nuts to prevent corrosion. This is because the high temperatures generated during braking cause technical greases to burn and the lines to become baked. The thread may only be protected if the car manufacturer permits it and specifies suitable lubricants. On the other hand, careful cleaning of the line and the contact surfaces between the hub and rim with a brush is always advisable.
- Mounting: The wheel comes on the hub, and the connections are loosely screwed. The best feeling in this step is manual work – with a socket wrench, ratchet or wheel cross. Applying and tightening the screws perpendicular to the thread axis is important. If they can be screwed in smoothly, they are not tilted. The often hemispherical or conical bolt shanks help with centring. The jack can be lowered if the wheel is correctly seated on the hub.
- Sequence: This is followed by the safety-relevant final tightening of the bolted connections. This should be done in a specific order and to the torque specified by the manufacturer. For hubs with four bolted connections, proceed crosswise (for example, 1-3-2-4). If there are five or six bolted connections, a star pattern changes. This procedure is important; it presses the rim evenly flush on the hub.
- Torque: To comply with the torque specified by the manufacturer in Newton meters (Nm), the bolted connections must be neither too loose nor too tight. A torque wrench with an appropriate setting range is the right tool.
The Nm specification can be found in the vehicle documents or, in the case of aftermarket rims, in the corresponding expert report. Very often, the value is 110 or 120 Nm. The most convenient way to tighten is with a releasing torque wrench: It is set to the desired value or is set to this value at the factory. When the limit value is reached during screwing, it turns with audible cracking.
- Check: High dynamic forces act on wheel bolts while driving. This is why it is often recommended to check the friction-locked connection shortly after the wheel change. The check is carried out about 100 kilometres after the wheel change by retightening all the bolted connections with the torque wrench. Again, work crosswise.
Useful knowledge about wheel bolting
The fastening of the rim on the hub differs in the arrangement of the threaded bolts: For wheels with wheel nuts, these are stud bolts on the corner. The edge can be positioned easily by sliding it over the fixed studs. Then the nuts are screwed on. On the other hand, wheel bolts bring the threaded stud and are turned into internal threads of the hub. This makes assembly a bit trickier. But in return, among other things, a larger number of rims can be approved for a car because bolts of different lengths can be used.
There are also differences in terms of the type and size of the fastener drive. Hexagon nuts for width across 17, 19 and 21 millimetres flats are widely used. Screws are available with external and internal hexagons or multi-tooth profiles. In addition, there are special anti-theft versions. It sounds a bit complicated, but in practice, it’s quite simple if you buy the right fasteners when you buy your wheels or make sure that the manufacturer’s standard equipment is suitable. It is easier to determine the number of holes in a rim: Three, four, five or six holes – that’s how many bolts or nuts are needed per wheel. Depending on the type of wheel, twelve to 24 connections have to be loosened and securely screwed back on when changing wheels on a car.
Until the middle of the 20th century, center locks were common, especially on sporty vehicles. These get by with a single, large wheel nut. A mighty wooden hammer blows open or closes the attached short key. Today, super sports cars and racing cars have similar locks. However, high-precision compressed air impact wrenches have long been used for these. In Formula 1, for example, a team of mechanics surrounds the car during the pit stop—one person for each operation. After two seconds, the top teams have changed all four wheels.
Rubber compound and tread
Chemistry and mechanics make the difference between summer and winter tires: they have different rubber compounds and profiles. Warm-season tires are made of a harder, stable combination even at higher temperatures and provide good traction on the road. A sensible compromise, especially in latitudes with a moderate climate, can be all-season tires with the “snowflake symbol” – the marking that the tire meets the legal requirements for unrestricted winter suitability.
Whether summer or winter: A tread depth of at least 1.6 millimetres is required by law. For safety reasons, GTÜ recommends new tires with four millimetres remaining tread depth.
When it’s time to change the wheels, check the stored set for damage and age: Information about this is provided by the four digits at the end of the DOT marking on the tire’s sidewall (the abbreviation stands for “Department of Transport”). The sequence of numbers is not read off as a calendar year but as a combination of the calendar week (numbers 1 and 2) and the year (numbers 3 and 4). A tire manufactured in the 47th calendar week of the year 2022 thus bears the digit 4722 at the end of the DOT markings. Knowing the tire’s age is important, emphasizes GTÜ: Even with sufficient tread, a tire has reached its service life after eight to ten years and should be replaced.
- source: krone.at/picture: Bild von Ulrike Mai auf Pixabay
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