Width
Tire section width is the distance between the sidewalls of an inflated but not loaded tire. As a rule, this parameter is indicated in millimeters, but there are also inch designations for the profile width.
Width is one of the characteristics that determines the compatibility of a tire with a specific wheel (the second characteristic is the mounting size). It is worth noting that the width of the tire does not have to strictly correspond to the width of the rim; certain deviations are allowed. There are special tables that allow you to determine the permissible width values for a particular wheel; in addition, such recommendations may be indicated in the documentation for a specific car.
The following tire width options are available on the modern market:
135 mm,
145 mm,
155 mm,
165 mm,
175 mm,
185 mm,
195 mm,
205 mm,
215 mm(in inches this is
8.5”),
225 mm,
235 mm,
240 mm(in inches this is
9.5”),
245 mm,
255 mm,
265 mm(in inches this is
10.5”),
275 mm,
285 mm,
290 mm(in inches this is
11.5”),
295 mm,
305 mm,
315 mm,
320 mm(in inches this is
12.5”),
325 mm,
335 mm,
345 mm(in inches this is
13.5”) and
over 345 mm(
over 13.5”).
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.
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.
