Load index
The maximum weight load that the tyre is able to carry. It is denoted by a conditional figure, each of which corresponds to a certain value:
66 - 300 kg, 67 - 307 kg, 68 - 315 kg, 69 - 325 kg, 70 - 335 kg, 71 - 345 kg, 72 - 355 kg, 73 - 365 kg, 74 - 375 kg, 75 - 387 kg, 76 - 400 kg, 77 - 412 kg, 78 - 425 kg, 79 - 437 kg, 80 - 450 kg, 81 - 462 kg, 82 - 475 kg, 83 - 487 kg, 84 - 500 kg, 85 - 515 kg, 86 - 530 kg, 87 - 545 kg, 88 - 560 kg, 89 - 580 kg, 90 - 600 kg, 91 - 615 kg, 92 - 630 kg, 93 - 650 kg, 94 - 670 kg, 95 - 690 kg, 96 - 710 kg, 97 - 730 kg, 98 - 750 kg, 99 - 775 kg, 100 - 800 kg, 101 - 825 kg, 102 - 850 kg, 103 - 875 kg, 104 - 900 kg, 105 - 925 kg, 106 - 950 kg, 107 - 975 kg, 108 - 1000 kg, 109 - 1030 kg, 110 - 1060 kg, 111 - 1090 kg, 112 - 1120 kg, 113 - 1150 kg, 114 - 1180 kg, 115 - 1215 kg, 116 - 1250 kg, 117 - 1285 kg, 118 - 1320 kg, 119 - 1360 kg, 120 - 1400 kg, 121 - 1450 kg, 122 - 1500 kg, 123 - 1550 kg, 124 - 1600 kg, 125 - 1650 kg, 126 - 1700 kg, 127 - 1750 kg, 128 - 1800 kg, 129 - 1850 kg, 130 - 1900 kg, 131 - 1950 kg, 133 - 2060 kg.
While choosing according to this indicator, it is worth considering not only the maximum weight of the car for which tyres are going to buy, but also the distribution of weight along the axles. With passenger cars, everything is simple — the weight is distributed approximately equally, so to determine the load on each wheel, it is enough to divide the maximum mass of the car by 4 (the number of wheels). H...owever, in minibuses, light trucks and SUVs, the situation is different: the weight distribution can be unequal, so you should refer to the manufacturer's documents or other special sources to calculate the load on each wheel.
Anyway, the load index must not be exceeded — this creates the danger of an accident. In fact, the wheel load should be at least 10 – 15% below the maximum, this will give an additional guarantee in case of abnormal loads. Also note that in some high-speed tyres, with the speed maximum approaching, the permissible load decreases: for example, for tyres with the V index (see "Speed rating") with speed over 210 km/h, it is recommended to reduce the load by 3% for every next 10 km/h increase in speed, similar recommendations apply to models with indexes W and Y. These details are usually described in the manufacturer's documentation and other special sources.
Run Flat
A technology that allows the tyre to maintain its performance even being flat. If a
conventional tyre fails after a maximum of a couple of kilometers with a loss of pressure, then you can drive several tens of kilometers on
RunFlat tyre without any problems — this is usually enough to get to the nearest tyre service. Similar properties are achieved due to the reinforced structure, particularly the increased rigidity of the sidewalls. Different manufacturers may use names other than Run Flat for this technology, such as Flat Run or Zero Pressure.
We note separately, that tyres with this feature can only be used on vehicles equipped with a tyre pressure monitoring system. Without such a system, it is likely that the driver will not notice tyre damage immediately — and this is fraught with several unpleasant consequences at once. Firstly, you can miss the time needed to correct the situation — as a result, the resource of a flat tyre may not be enough to normally get to the workshop or service station. Secondly, driving on a run flat tyre requires slowness and special care, driving in a normal style on such a tyre can lead to loss of control.
Wear resistance (Treadwear)
Tyre wear resistance rate according to the Treadwear standard issued by the US National Highway Traffic Safety Administration.
This rate indicates how far the tyre is able to travel until the tread reaches a critical level of wear. Treadwear is indicated in conditional points; formally, every 100 points correspond to 48,000 km (30,000 miles). However, it should be noted that testing according to this standard is carried out under perfect conditions — on flat roads, without numerous sharp accelerations and brakings, at a stable temperature, etc. Therefore, real wear resistance, usually, is lower by at least 20 – 30 %; and for a full guarantee, the claimed indicator is generally recommended to be divided by two. For example, formally the value of Treadwear 240 corresponds to a mileage of 48 × 2.4=115.2K km — however, in fact it is hardly worth counting on more than 90K km, and it is best to keep on the value of 55 – 58K km.
Generally, Treadwear ratings up to 250 are considered fairly low, 251 – 300 are considered average, 301 – 350 are above average, and over 350 is typical for
the most durable tyre models. Note that this characteristic is given mainly for summer, less often — all-weather tyres; winter tyres should be quite soft, which makes it difficult to achieve more or less worthy wear resistance rating.
