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Summer tires now? Five tips for changing tires

Anyone who keeps the wheel cross like this is already making the first mistake.

(Bild: stock.adobe.com)

Winter tires are still mandatory until April 15, but if you don't find yourself in winter driving conditions, you can change to summer tires at any time. Or change them yourself if the stored tires are still good. We explain here what you need to bear in mind.

It looks so simple, but you can do a lot of things wrong 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 similar into the thread. But in detail:

Five steps to a successful wheel change

1. check: Once the winter wheels have been removed, you should first check the summer wheels and the threads and drives of the wheel bolts or wheel nuts for any damage. Does everything look good? Then fitting can begin.

A 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 threads to bake. The thread may only be protected in this way if the car manufacturer expressly permits it and specifies suitable lubricants. Careful cleaning of the thread and the contact surfaces between the hub and rim with a brush is always advisable.

2. mounting: Now the wheel is placed on the hub and the connections are loosely bolted together. This step feels best done by hand - with a socket wrench, ratchet or wheel cross. It is important to position and tighten the bolts perpendicular to the thread axis. If they can be screwed in smoothly, they are not tilted. The screw shafts, which are often hemispherical or conical, help with centering. If the wheel is correctly seated on the hub, the jack can be lowered.

3. sequence: This is followed by the safety-relevant, final tightening of the screw connections. This should be carried out in a specific sequence and to the torque specified by the manufacturer. For hubs with four screw connections, proceed crosswise (for example 1-3-2-4). If there are five or six screw connections, replace them in a star pattern. This procedure is important as it presses the rim evenly flush onto the hub.

4. torque: In order to maintain the torque specified by the manufacturer in Newton meters (Nm), the screw connections must be neither too loose nor too tight. A torque wrench with the appropriate setting range is the right tool.

The Nm specification can be found in the vehicle documents or, in the case of retrofit rims, in the corresponding certificate. The value is very often 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 tightening, it continues to turn with an audible click.

5. check: High dynamic forces act on wheel bolts while driving. This is the reason why it is often recommended to check the friction-locked connection shortly after changing the wheel. The check is carried out around 100 kilometers after the wheel change by tightening all screw connections again with the torque wrench. Again, work crosswise.

Useful knowledge about wheel bolting
The basic difference between fastening the rim to the hub is the arrangement of the threaded bolts: For wheels with wheel nuts, the bolts are studs on the hub. The rim can be positioned particularly easily by sliding it over the fixed studs. The nuts are then screwed on. Wheel bolts, on the other hand, come with the threaded bolt and are screwed into the internal thread of the hub. This makes fitting a little trickier. On the other hand, a larger number of rims can be approved for a car because different lengths of bolts can be used.

There are also differences in the type and size of the drive of the fasteners. Hexagon nuts for wrench sizes of 17, 19 and 21 millimetres are widely used. Screws are available with external and internal hexagon or multi-tooth profiles. There are also special anti-theft versions. Sounds a little complicated, but in practice it's quite simple if you buy the right fasteners when you buy the 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 design, there are between twelve and 24 connections that need to be loosened and securely tightened again when changing wheels on a car.

Until the middle of the 20th century, central locking systems were common, especially on sporty vehicles. These make do with a single, large wheel nut. Powerful blows of a wooden hammer open or close the attached short key. Today, super sports cars and racing cars have similar locks. However, high-precision pneumatic 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 every movement. After two seconds, 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. The tires for the warm season consist of a harder compound that is stable even at higher temperatures and provides good traction with the road surface. All-season tires with the "snowflake symbol" can be a sensible compromise, especially in temperate climates - this indicates that the tire meets the legal requirements for unrestricted winter suitability.

Whether summer or winter: A tread depth of at least 1.6 millimeters is required by law. For safety reasons, GTÜ recommends new tires with a remaining tread depth of four millimeters.

When it is time to change the wheels, check the stored set for damage - and for age: The four digits at the end of the DOT marking on the sidewall of the tire (the abbreviation stands for "Department of Transport") provide information about this. The number sequence is not read as a calendar year, but as a combination of the calendar week (digits 1 and 2) and the year (digits 3 and 4). A tire manufactured in the 47th calendar week of the year 2022 therefore bears the numbers 4722 at the end of the DOT markings. It is important to know the age of the tire, emphasizes the GTÜ: A tire has reached its service life after eight to ten years, even with sufficient tread, and should be replaced.