Construction and marking of tires (Fiesta 4)

Fig. 13.30. Designations on the sidewall of the tire: 1 – tire marking: 215 – tire width in mm; 55 – the ratio of the tire profile height to its width in percent; ZR - radial tire; 16 – landing diameter in inches; 93 – load (650 kg); Y — maximum speed (300 km/h); 2 - North American data: maximum permissible load and maximum permissible air pressure, as well as safety instructions; 3 – direction of tire rotation; 4 – design: data on the quantity and material of the tread and sidewall of the tire; 5 – radial tire: in a radial tire the cord is located at an angle of 90° to the direction of rotation of the tire; 6 – Tubeless tire: the inner air-tight layer replaces the tube; 7 – MFS wheel rim protection; 8 – Tread Wear Indicators TWI: The "TWI" marking or triangles on the sidewall of the tyre indicate the location of the tread wear indicators. When the minimum profile depth (1.6 mm) is reached, the transverse plates are exposed; 9 – inspection signs: number E – the tire complies with European ECE-R30 regulations; digit 4 – code of the country where the tire was tested (Netherlands); 10 – DOT symbols: the tire complies with the requirements of the US Department of Transportation DM 6P 38 T – DOT code (coding of the manufacturer, size and construction of the tire): 219 – date of manufacture (the first and second digits are the week of manufacture, the third digit is the year of manufacture); in the example: week 21 of 1999 (since 2000, a four-digit notation has been used, e.g. 1500 – week 15 of 2000)



The characteristics of modern tires — size, external load, internal pressure and maximum recommended speed — are standardized to ensure interchangeability of tires during their use (Fig. 13.30). According to current global agreements, tire size is given in millimeters or in millimeters and inches simultaneously. For example, the marking 155/70 R 13 means that the width of the tire in an unloaded state is 155 mm. The next two digits indicate the ratio of the height to the width of the cross-section of the tire profile — 70%. The smaller this ratio, the flatter and wider the tire. The letter "R" characterizes the tire design — radial (a tire with a radial arrangement of cord threads). The subsequent digits determine the inner diameter of the tire in inches. When purchasing a new tire, pay attention to its characteristics: the new tire must fit the rim.

Only radial tires are installed on passenger cars.



Fig. 13.31. PKW-Reifens radial tubeless tyre: 1 – tread (profile and position affect the tyre quality); 2 – base (reduces rolling resistance); 3 – Nylon cord (increases resistance to high speeds); 4 – steel breaker (increases driving stability); 5 – tire frame (provides the shape and strength of the tire); 6 – airtight inner layer replacing the camera; 7 – sidewall (protects the frame from damage); 8 – board (maintains precision control and movement); 9 – bead core (ensures a secure fit on the rim); 10 – reinforcing thickening (increases control precision and driving stability)



In radial tires, the cord threads are arranged along the shortest path between the tire beads. The breaker belt surrounds a thin and elastic carcass and provides stability to the tire (Fig. 13.31).

Tubeless tires are characterized by a vulcanized inner layer with high air permeability. The sidewall of such a tire must be installed on the wheel rim securely and hermetically. The absence of a tube in the tire reduces the weight of the wheel and simplifies its installation on the wheel rim.

Speed index - capital letter after the last digit

The capital letter following the last number on the sidewall indicates the maximum speed rating of the tire.

The 155/70 R 13 tire with the letter "S" can be used up to a maximum vehicle speed of 180 km/h, with the letter "T" - up to 190 km/h. Tires with the "H" marking are intended for a maximum speed of 210 km/h. Regular tires (M+S) with the "Q" marking are designed for speeds up to 160 km/h.

The DOT symbol indicates the age of the tire

Fig. 13.32. The ECE test number is determined by the capital letter "E" and the number of the country of origin, e.g. "1" for Germany, "4" for the Netherlands



The actual date of manufacture of a tyre is determined by the DOT number on the sidewall of the tyre: since 1990, a small triangle has been placed after these numbers. DOT number 1500 means that the tyre was manufactured in the 15th week of 2000. New tyres manufactured since 1 October 1998 must have an ECE test number on the sidewall (Fig. 13.32). Each test number guarantees that the tyre has passed the tests according to the quality standard of the Economic Commission for Europe (ECE-R30). If your vehicle is equipped with tyres with a DOT number higher than 408 and without an ECE test number, you are using a tyre without a "general approval".

Winter tires

Fig. 13.33. Comparison of braking distances for summer and winter tires on a vehicle without ABS: 1 – braking on ice with wheel lock (speed 30 km/h); 2 – winter tires; 3 – braking distance; 4 - summer tires; 5 – braking distance



Fig. 13.34. Comparison of the braking distance values of summer and winter tires of a car with ABS: 1 – braking with ABS on a snowy road (speed 50 km/h); 2 – winter tires; 3 – braking distance; 4 - summer tires; 5 – braking distance



Even for use on autumn roads, winter tires must be installed on the car, and in winter you cannot do without them at all. This is due to the fact that the working surfaces of the tires are made of a special material based on rubber with a high content of natural rubber. The grip of such tires on the surface of wet, slippery roads and at temperatures below 7°C is much better than that of ordinary summer tires (Fig. 13.33, 13.34). The minimum profile depth of winter tires is 4 mm. In any case, replace summer tires with winter tires on all four wheels - a combination of summer and winter tires is dangerous.

It is better to install winter tires on your own wheels

Summer tires are prone to slipping on snow and ice, so when driving a car in the winter, it is recommended to install a set of tires with a winter tread pattern. Regardless of what tires are installed on the car, at temperatures near freezing, a thin film of water forms on the ice, which reduces the traction of tires, including winter tires.

Good winter tires should not be wide. Although narrow tires are cheaper than wide ones, the money saved will have to be spent on a second set of suitable rims, because constantly removing and installing summer and winter tires worsens their quality - it is better to buy a second set of rims. By the way, after each tire change, the wheels must be rebalanced. The pressure in winter tires should be maintained at 0.2 bar more than in summer tires. If the permissible maximum speed of your winter tires is lower than the permissible maximum speed of the car, stick a warning label on the dashboard.

Checking cold tire pressure

It is necessary to measure the air pressure only in cold tires - during movement they warm up, and the pressure in them increases. As a result, you get inaccurate measurement results. Check the tire pressure every three to four weeks, the normal pressure loss per month should be 1.5%. If the pressure loss is greater, check the condition of the tire. If the air pressure in heated tires is increased, do not release air from the tire. If the load changes significantly, the air pressure in the tires should be changed accordingly.

Standard values of air pressure in cold tires are given in Table 13.2.

Protective caps for tire valves

Tire valves should always be covered with protective caps, as dirt, once it gets into the valve, will compromise the seal of the tire and the pressure in the tire will constantly decrease.



Fig. 13.35. Tire delamination due to overheating due to too low air pressure in the tire



Never allow the tires to be used with low pressure, as this will cause their temperature to exceed the permissible limit, which will sooner or later lead to tread separation or the tire will burst (Fig. 13.35). Higher air pressure (by 0.2–0.3 bar) can even be beneficial: the steering becomes more sensitive and fuel consumption decreases slightly, but the car moves "harder".



PRACTICAL TIPS

Careful use of tires

1. Never exceed the speed limit for your tires. This applies especially to tires (M+S) of category "Q" (160 km/h). At higher speeds, tires wear out more, and in the worst case, the tire may burst.

2. Avoid maximum speed with a fully loaded car. Check the tire temperature: if it is equal to body temperature, then everything is normal. Hot rubber is an alarm signal that indicates too low tire pressure or damage to the tire frame. Immediately dismantle such tires and give them to a specialist for inspection.

3. If you often drive on the highway at high speed, install tires with a speed index that is an order of magnitude higher than that indicated in the technical data sheet, for example, "T" instead of "S".



4. When parking, try not to let the sidewalls of your tires hit curbs and other obstacles – you should drive over them at low speed and at a right angle.

5. Increase tire pressure by 0.3 bar - this measure will save fuel without damaging your tires.