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All about tires

Basic tire sizes

What is the meaning of the alphanumeric information on the tire?

185/65 R 14 85 T

185 nominal width of the tire (mm)
65 aspect ratio  (%)
R identifies the tire’s radial construction
14 nominal diameter of the rim in inches
85 load index
T speed index

Load index

Load rating (LI) – is a number defining the load capacity of the tire at the speed defined by the speed rating under given specific conditions.
 
Li kg LI kg LI kg LI kg LI kg
50 190 65 290 80 450 95 690 110 1060
51 195 66 300 81 462 96 710 111 1090
52 200 67 307 82 475 97 730 112 1120
53 206 68 315 83 487 98 750 113 1150
54 212 69 325 84 500 99 775 114 1180
55 218 70 335 85 515 100 800 115 1215
56 224 71 345 86 530 101 825 116 1250
57 230 72 355 87 545 102 850 117 1285
58 236 73 365 88 560 103 875 118 1320
59 243 74 375 89 580 104 900 119 1360
60 250 75 387 90 600 105 925 120 1400
61 257 76 400 91 615 106 950 121 1450
62 265 77 412 92 630 107 975 122 1500
63 272 78 425 93 650 108 1000 123 1550
64 280 79 437 94 670 109 1030 124 1600

Speed ratingi

Speed rating (speed symbol - SS) is the maximum speed at which the tire may carry the weight defined by the load index under given specific conditions. The tire speed symbol for passengers and commercial vehicles is defined by capital letters.
 
Symbol  L M N P Q R S
Max. speed [km/h]  120 130 140 150 160 170 180
Symbol  T U H V W Y ZR
Max. speed [km/h]  190 200 210 240 270 300 >240
Because the depth of the tire tread during the use is gradually reduced, the vehicle braking distance, particularly on a wet rod, becomes significantly longer.

The danger of aquaplaning (i.e. the loss of contact of the vehicle with the road due to a water column between the tire and the road surface is therefore greater with tires which have a small residual depth of the tread groove.

Worn out tires 

From the aspect of road traffic safety, it is therefore most important to replace a worn tire with a new one, i.e. before the residual or safe depth of the groove is reduced to less than 1.6 mm. The size of the minimal safe groove depth is signaled by so called wear indicators which are the projections at the grove bottom which are also 1.6 mm high.

Evenly worn treads of all tires on the vehicle prolong their life and thus increase driving economy and contribute towards higher driving safety. Therefore especially for front-wheel drive vehicles we recommend to swop the tires from front to rear and vice versa in certain regular intervals (e.g. every 5,000 km) while making sure that the wheel rotation direction is maintained.

Tire repairs

Tire repairs are from the driving safety point of view are a very demanding and responsible operation, and therefore they should be always carried out by a specialist. 

All damaged spots on a tire must be permanently repaired. Hence it is not acceptable to install a tube inside a non-repaired tire as a an alternative solution.
We do not recommend to use sealing repair sprays for permanent repairs, but always only to complete the trip, nor we recommend repairing a tire with special pre-vulcanizing plugs without removing it from the wheel rim.

Repairing damage which extends to the tire, body plies or carcass must be done using either the hot or the cold vulcanization method after a thorough examination and preparation of the damaged spot on the tire. 

All repairs should be done as soon as possible after the damage has occurred, otherwise (especially in case of tires with steel belts) the damage might spread or the tire may even be destroyed as a consequence of dirt and water penetration. Re-cutting the tread of passenger car tires is prohibited.

Storage 

Tires fitted on wheel rims must be stored either stacked on top of each other or hanging.
Lose tires must be stored upright next to each other (see Figure). However, to prevent thus stored tires from getting deformed, it is recommended to turn the tires every approximately 14 days. In any case, it is recommended to have the tires at the end of the season, before fitting them on rims, balance at tire service

How to store tires correctly

Tires and tubes must be stored in dark, dry and cool premises free of draft. Excessive exposure to sunshine, heat and draft is harmful to these products and is the cause of premature aging which manifests itself in the form of fine cracks developing in the rubber surface. Furthermore, tires and tubes must not get into contact with products of petroleum origin (such as oils, motor fuels, lubricants, etc.), as these make rubber spongy and it loses its elastic properties of a vulcanizate.

Our Tip

If you don’t have suitable storage space, have your tires stored by our service partners where we guarantee that your tires will be stored correctly and thus ensure their long life. 

Choosing tires

What tires to use for a particular type of a vehicle is specified by the vehicle’s manufacture together with the tire manufacturer, whereby it is permissible to use tires with higher speed symbol, e.g. ‘H’ instead of ‘S’. It is also permissible to use tires of a higher load index, e.g. 82 instead of 80. When replacing tires for a different size, legislative regulations must be respected, i.e. the new tires must be recorded in the Vehicle Registration Certificate.

Optimal vehicle driving properties can be achieved only with tires of the same type. This means that the vehicle must have (with the exception of the “space saver” spare tire), tires of identical size and construction, whereby on the same axle must be used identical tires (i.e. tires of the same size, construction, type of tread and brand). As the construction of passenger car tires is in this case understood diagonal, radial-textile (the carcass as well as the body plies are made of textile cords), and radial-steel (carcass – textile plies, body plies – steel belts) construction. Combination of tires of these two constructions on the same vehicle is not permitted.

For M+S (mud and snow) winter tires we recommend for safety reasons to use these always on the whole vehicle, not only on the same axle. Combination of winter and summer tires is acceptable only provided the residual depth of the winter tire tread is < 40 mm, i.e. below the limit at which winter tires lose their specific winter properties.

A tire change very often requires also a change of wheel rims. Therefore when choosing wheel rims, the recommendations of their manufacturer must also be respected, and the change of rims must be recorded in the Vehicle Registration Certificate.

Steel rim identifiers

​5 1/2 J x 14 H2 
This is a wheel with deep rim, 51/2” wide, J-type flange, rim width 14 inches and “double-hump” style ridges.

5,50 B x 14 CH 
This also a wheel with deep rim and width 51/2”, but with a B-type flange, diameter 14 inches and “combination hump” style ridges.

14 x 5 1/2 J H2 x 45
This is again a wheel with deep rim and width 51/2”, Type 3 flange, diameter 14 inches and “double-hump” style ridges. The alphanumeric marking includes an additional information, the wheel offset.

Determining a minimum possible tire size for a particular vehicle inevitably requires to know the maximum permissible load on axles and the vehicle’s design speed. On the tire, its maximum load capacity is expressed by the load index, and maximum speed by the speed symbol.

When the wheels are deflected from straight direction by 2° to 4°, the load capacity reduces by 5% per degree. This reduction in load capacity can be compensated by increasing the tire air pressure.

Load capacity in two-wheel configurations is 1.85 of the capacity of tires in a single-wheel configuration.
 

Reduced tire load versus speed


Increasing the load capacity by up to 10% of table values is permissible also for tires used on caravans or trailers of maximum cruising speed 100 km/h. In such case the base tire pressure must be increased by 20 kPa.

The load bearing capacity of passenger car tires can be increased only on vehicles the maximum speed of which does not exceed 60 km/h, and this under the condition that the tire pressure is increased in accordance with the table ‘Maximum speed versus increased load capacity.

Reduced tire load versus speed

Maximum vehicle speed Speed index (tire load in %)
(km/h) 
H
V
W
RZ
210
100
100
100
100
220
 
97
100
100
230
 
94
100
100
240
 
91
100
100
250
 
 
95
100
260
 
 
90
100
270
 
 
85
100
280
 
 
 
95
290
 
 
 
90
300
 
 
 
85
 
Maximum vehicle speed
Increased load capacity
Increased tire pressure
(km/h) 
(%) 
(kPa) 
60
10
10
50
15
20
40
25
30
30
35
40
25
42
50

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Ask us – we will be glad to help you and reply.
*In order to be able to use RunOnFlat tires, your vehicle must have an integrated tire pressure monitoring system. Please check the technical documentation of your vehicle provided by its manufacturer.

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