It is a well-known fact that the choice of tyres and wheel rims is essential to a safe journey: sometimes people don't consider the two components important and when it comes to buying them, they often prefer to save money. They couldn't be more wrong: not all tyres can be adapted to your car model, and the same applies to wheel rims. The first element to consider is the type of vehicle: since the tyres on a 4x4 differ from those of a city car or a coupé, simply check the vehicle registration document (or the owner's manual) to read what the correct size is for your car and choose accordingly at the time of purchase.
The marking
It is important to know how to read the markings, i.e. the information written on the sidewall (width, height of the sidewall, diameter, construction, load index and speed rating). An example to understand better is a 225/55 R 17 97 W marking: 225 is the nominal section width of the tyre in mm; 55 is the tyre series, indicating the ratio of the height of the tyre sidewall to the section width of the tyre; R means that the construction of the tyre is radial; 17 is the diameter of the wheel rim, expressed in inches; 97 is the load index and corresponds to the maximum load the tyre can withstand at the speed indicated after; W is in fact the speed rating and indicates the maximum speed at which the tyre can withstand the maximum load indicated previously. For over ten years, all tyres made in the Old Continent have been required to bear the European label, consisting of three items, indicating energy efficiency, safety and noise respectively. For winter tyres, there is also an indication whether they are specific for ice or snow.
Driving style
Another important parameter in the choice of tyre is driving style.
People who do a lot of urban driving consume a lot of fuel and have to brake and accelerate frequently: in this case the best choice is a long-life tyre, which offers excellent braking distances and low rolling resistance. On the other hand, drivers who travel on the motorway a lot need reliable tyres in any weather, which will provide maximum comfort levels, even at high speeds. Enthusiasts of sports driving need tyres with excellent grip and outstanding road holding (especially when cornering) and superior performance levels (high performance and ultra high performance). Last but not least, fans of off-road driving need to be able to rely on tyres designed for 4×4 traction, which guarantee safety in extreme conditions.
The choice of wheel rims
The measurements used to indicate the wheel rim are the rim width and the diameter. For instance, if the wheel rim is a 16x7J size, 16 indicates the rim diameter, expressed in inches; 7 is the rim width; J is the shape of the outer edge of the rim. By “playing” with the wheel rim width, the wheel can protrude more or less: for instance, if you increase the former, the wheel will protrude more; however, if you increase it too much, you run the risk of the tyre coming away from its seat. Another element to bear in mind is the offset (also known as ET), in other words the distance between the hub mounting surface and the wheel's symmetry axle, expressed in mm. The bigger the offset, the more the rim will fit on the axle; if you oversize it however, the wheel risks touching the brake straps or the shock absorbers. On the contrary, the smaller the offset, the more the rim protrudes towards the wheel; if this measurement is reduced too much, the wheel rim risks coming into contact with the bodywork. For the best choice of wheel rim, it is always worth consulting the wheel/tyre equivalence chart, which correlates the ideal models to purchase based on the minimum and maximum tyre widths.
