# Tyre Size Calculator

## Checking Tyres

Tyres are the only part of your vehicle that is continuously in contact with the road, and their condition greatly affects your safety. Bad  tyres can decrease your car’s performance, reducing the efficiency of braking, steering, speeding and driving comfort. Therefore, it is necessary to take care of your tyres and check them occasionally.

### Overall Tyres Condition – Visual Inspection

Once in a while, when approaching your vehicle, you should check the following:

• Are the tyres deflated?
• Is there any physical damage on the sidewalls; are there any cuts or deformities?
• Is the tread damaged by gravel, nails or other foreign objects?
• Is there a nail in your tyre?
• Do all the valves have their caps on?

### Tyre Pressure

• Check tyre pressure at least once every two weeks
• Measure tyre pressure only when they are cold
• Make sure you only pump your tyres up to the value prescribed by the car manufacturer which is located in the car’s manual
• When going on a long trip, increase your tyre pressure by 0.2 bar above the prescribed

While driving, tyres worm up which leads to an increase in pressure. This is the reason why you should measure tyre pressure only when your tyres are cold, or at least one hour after you have finished driving. The temperature in the garage may differ from the outside temperature by 30°C. For example, if the temperature in the garage is +20°C, and the outside temperature is -10°C, tyre pressure measured inside must be 0.3 bar higher in order to have proper pressure outside. So you should increase/decrease your tyre pressure by 0.1 bar for each 10°C difference in temp.

To conclude, improper tyre pressure diminishes the efficiency of braking, steering, speeding and driving comfort. In case of a rupture while driving, or a sudden drop in pressure, you should immediately stop the car. It is not advisable to drive with deflated tyres because it may result in permanent damage.

Tread depth of a new tyre is 7-8 mm. Once the tread depth drops below 3 mm the tyre looses its original properties. Even though tyres usually get replaced when their tread depth is less then 1 mm, we advise you to change tyres when it drops under 2 mm.

### Tyre Wear Indicator

Tyre wear indicator looks like a triangle and is located on the sidewall of the tyre. It indicates the minimum tread depth. The letters TWI or manufacturers logo are alternative indicators of wear on the sidewall. The tyres should be replaced before the tread reaches tyre wear indicator.

### Spare tyre

Even if you have never used a spare tyre before, make sure to regularly check its condition. You should regularly check its pressure and tread depth.

### Tyre Age

Don’t forget that tyres must not be older then 6 years! Occasionally check the DOT number marking on your tyre.

### Valves

From time to time you should check the valves. If they release air, the pressure in your tyres will not be correct. Be sure to replace the valves when changing tyres.