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.
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.
Fuel efficiency
The rolling resistance rating that the tyre corresponds to. The higher this figure, the lower the resistance, the less fuel is spent to overcome it and the more economical the tyre is. Efficiency indices are denoted by letters of the Latin alphabet in descending order of efficiency:
A(highest efficiency),
B,
C,
D,
E,
F,
G(lowest efficiency).
With other things being equal, more economical tyres tend to cost more, but the difference is offset by fuel economy.
Wet Grip
An index that determines the overall performance of a tyre on wet pavement. Lettered from
A(highest) to
G(lowest); intermediate options, respectively —
B,
C,
D,
E and
F.
The higher this indicator, the stronger the tyre grips to the wet road, the more efficient and safer it will be in difficult weather conditions. At the same time, it is worth noting that a low grip index does not mean unsuitability for driving in rain or snow — you just need to be more careful using such tyres. Conversely, a high index does not relieve the driver of the need to be careful in difficult weather conditions.
Noise Level
The average noise level created by a tyre while driving. The lower this indicator, the more comfortable this model will be, the less additional noise it will create.
Note that EU rules provide 3 categories of tyres in terms of noise.
“Quiet” are considered models with an index of up to 68 dB,
“medium” — 68 – 71 dB,
“loud” — 72 dB and above.
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.
