Season
The time of the year the tyres are designed for.
Tyres designed for the warm season are called
summer, for cold — respectively, winter (among the latter,
studded and
non-studded models are separated, see below for details). The need for separation by season is due to the fact that when the temperature drops, the rubber solidifies; therefore, cold weather requires softer tyres than warm weather. And the time when you need to change tyres is best determined by the average daily temperature: if it is above +5 °C, it is better to use summer tyres, if lower — winter ones. There are also more detailed recommendations regarding the time of changing tyres, they can be found in special sources.
Also note that there are tyres positioned as
all-weather. Such models should be treated with some caution: they can be produced in countries where winters are very mild, without snow and severe frosts, and be designed specifically for such “all-season”; for a full-mean winter, such tyres may not be suitable. So the specific attributes of all-season tyres should be specified separately (including reviews). If there are no detailed info, such tyres are best considered as summer tyres with slightly increased resistance to cold, and if used in winter, then in simple conditions (for example, driving along well-cleaned city streets).
Aspect ratio
Tyre aspect ratio. This parameter is usually expressed as a percentage of the width, since it is not the height itself that is of practical importance, but its ratio with the nominal section width.
In general, the lower the ratio, the more stable the tyre, the better it is suitable for high-speed driving on flat roads. Higher ratio, in turn, work better on rough surfaces and over obstacles, making them good for bad roads and
off-road. If we talk about specific numbers, nowadays, the following options are spread on the market:
— Low profile tyres:
25%,
30%,
35%,
40% ;
— Medium profile :
45%,
50%,
55%,
60% ;
— High profile :
65%,
70%,
75%,
80%,
82%,
85%, and
90% or more.
Tyre inner diameter
Tyre inner diameter in inches. The key parameter that determines the possibility of installing a tyre on a car: the tyre diameter must match the diameter of the rim. It is worth noting that some vehicles have +/- 1 inch diameter tolerance; this point should be clarified separately in each case.
In modern passenger vehicle tyres, the following rim diameters are most widely used:
12",
13",
14",
15",
16",
17",
18",
19",
20",
21",
22",
23",
24".
Speed rating
The speed rating that the tyre corresponds to.
This indicator determines the maximum speed that tyre is allowed to operate. It is designated by the letters of the Latin alphabet, each of which corresponds to a certain speed limit:
F — 80 km/h; G — 90 km/h; J — 100 km/h; K — 110 km/h; L — 120 km/h; M — 130 km/h; N — 140 km/h; P —
150 km/h ; Q —
160 km/h ; R —
170 km/h ; S —
180 km/h ; T —
190 km/h ; U —
200 km/h ; H —
210 km/h ; V —
240 km/h ; W —
270 km/h ; Y —
300 km/h ;
The maximum permitted speed must not be exceeded — this creates the risk of an accident. However, there are other rules associated with choosing a tyre by this factor. So, ideally, the actual driving speed should be at least 10 – 15% lower than the speed rating of the installed tyres — this will give an additional guarantee in case of emergency situations. In addition, in some tyre models, as the speed approaches the maximum, the upper limit of allowable load is reduced; see “Load Index” for details.
Orientation
The shape of the tyre tread pattern:
—
Directional. Pattern with a characteristic V-shape. Among other things, such rubber is considered to be especially effective on wet surfaces — in rain, on snow, with an abundance of melt water, etc.: the pattern provides effective water drainage, reducing the risk of hydroplaning and increasing grip. Also, these tyres are well suited for high-speed sports cars (although, of course, their speed rating and specialization may be different). When installing directional tyres, the direction indicated by the manufacturer must be kept.
—
Symmetric. The pattern without signs of directionality is the same both on the outer and on the inner part of the tread. These tyres are easier to manufacture than directional or asymmetric tyres, and are generally cheaper, while still having good performance on a flat and dry surface. In addition, symmetric tyres are as simple as possible to install, they do not need to follow the direction. However, for hard conditions, particularly wet weather, they are poorly suited. So, typically, such tyres are designed mainly for city cars used on short trips on relatively high-quality roads.
—
Asymmetric. Tyres with a different pattern inside and outside the tread. Each of these parts plays a role: the inner part provides water evacuation and reduces the risk of aquaplaning, while the ou
...ter part provides the necessary rigidity for manoeuvrability and stability. While installing, you need to take into account the location of the outer and inner sides, they usually have the appropriate marking. Asymmetric tyres are considered the most advanced, although, of course, the actual characteristics and cost of such products may vary, depending on the brand and the general level. Such tyres are designed mainly for cars of medium and top levels; they are often supplied as factory equipment for advanced cars.
