Type
The type determines the installation location for which the tyre is designed. Different installation locations require different characteristics, which are taken into account in the design accordingly. It is impossible to violate compliance by type — this leads to off-design loads that increase tyre wear and can even lead to such a dangerous incident as a tyre “explosion”.
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Steering wheel. Tyres designed to be mounted on the steering axle of a truck. At this point, the wheels and tyres are subjected to additional torsional loads along the vertical axis (when the steering wheel is turned from side to side), which puts forward increased requirements for reliability.
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Leading. Tyres designed to be mounted on truck drive axles where good road grip and high resistance to torsional loads on the main axis of rotation are extremely important.
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Trailer. This category includes tyres intended exclusively for installation on trailers (as well as on other axles that are not steering or driving) and not suitable for other uses. With this setup, the torsional loads are relatively low, but the tyre is often subjected to heavy weight loads (for example, in truck tractors, most of the weight is on the trailer).
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Universal. Tyres that allow any of the installation options described above. This option is convenient
...because by purchasing a set of tyres of the same model, you can provide them with all the wheels of the truck at once, without buying other tyres. On the other hand, at the same cost, universal tyres are often inferior to specialized ones in terms of performance.
— Steering / trailer. Tyres best suited for either helm or trailer use. See above for more details on each of these options.Width
Tyre profile width in inches. Inches are the most popular width format; in addition to it, there is also a designation in millimetres. Formally, 1 inch corresponds to 25.4 mm, but in fact the correspondence is not so strict: for example, the width of a 13 ”tyre in millimetres is usually 315 mm, not 330 mm. So it is best to convert millimetres to inches and vice versa using special tables.
As for the width, in this case it is indicated by the distance between the sidewalls of the tyre mounted on the disk and inflated (but not loaded). This is one of the parameters that determine compatibility with a particular disc: the tyre must be slightly wider than the rim. For the selection of rubber for specific disks in width, there are special tables.
Among modern tyres for trucks and buses, there are such standard width options:
6.5",
7",
7.5",
8.25",
8.5",
9",
9.5",
10",
11",
12",
13",
14". Tyres for special equipment and agricultural machinery (see "Intended use") may have larger sizes.
Width
Tyre profile width in millimetres. This designation is noticeably less common than inches (see Width above), but it is also used quite widely.
As for the width in the frame, in this case it is indicated by the distance between the sidewalls of the tyre installed on the disk and inflated (but not loaded). This is one of the parameters that determine compatibility with a particular disc: the tyre must be slightly wider than the rim. For the selection of rubber for specific disks in width, there are special tables.
On the modern market, among the popular sizes, there are such options in width:
205 mm,
215 mm,
225 mm,
235 mm,
245 mm,
265 mm,
275 mm,
285 mm,
295 mm,
305 mm,
315 mm,
385 mm,
425 mm,
435 mm,
445 mm.
Aspect ratio
Tyre profile height. This indicator determines how much the tyre protrudes above the disk. Specifies the profile height as a percentage of the width (see above). The lower the profile, the better the stability of the car on the road and the faster the rubber wears out; in turn, higher profiles are well suited for rough roads, primers and off-road.
In truck tyres, there are such options for profile height:
40%,
45%,
50%,
55%,
60%,
65%,
70%,
75%,
80%,
85%,
90%,
95%.
Load index
The load index characterizes the maximum weight under which the tyre can be safely operated. As in the case of the speed rating described above, this indicator cannot be exceeded, otherwise unpleasant consequences are possible, up to accidents. Also note that when selecting according to the load index, it is worth considering the distribution of weight along different axes of the vehicle. And it is worth considering the maximum possible weight when the truck is loaded, in accordance with what to select
truck tyres for heavy loads.
Speed rating
The speed rating describes the maximum speed at which a given tyre can be safely driven. It is worth choosing a model according to this parameter in such a way that during operation it is not allowed to exceed the speed rating — this creates increased loads on the tyre and can lead to its damage (up to an “explosion”). And it is best to choose an option with a margin of at least 10 – 15 km/h — this will give an additional guarantee in case of emergency situations. For truck tyres, speed indices in the range of 100 – 130 km/h are considered popular, and these are
the J speed rating(100 km/h),
the K speed rating(110 km/h),
the L speed rating(120 km/h) and
the speed rating M(130 km/h). For agricultural machinery, the speed is much lower:
index A6(30 km/h),
index A8(40 km/h),
index B(50 km/h),
index D(65 km/h),
index F(80 km/h) ). There are also
high-speed truck tyres and less popular
speed indices C(60 km/h),
E (70 km/h) and
G (90 km/h).
