The tyre load capacity indicated in the load index are the maximum loads per tyre permitted for all tyres up to the speed symbol ‘H’. They are valid up to speeds of 210 km h-1 for tyres marked ‘V’ and up to 240 km h1 for those marked ‘R’ ‘W’ or ‘ZR’. For vehicles with a higher top speed, the load capacity has to be reduced accordingly.
Consequently, for tyres with speed symbol ‘V’, at a maximumspeed of 240kmh-1 the load capacity is only91% of the limit value . Tyres designated ‘W’ on the sidewall are only authorized up to 85% at 270 km h–1. In both cases, the load capacity values between 210 km h-1 (‘V’ tyre) and 240 km h-1 (‘W’ tyre) and the maximum speed must be determined by linear interpolation.
For higher speeds (ZR tyres), the interpolation applies to the 240–270 km h-1 speed range. At higher speeds, the load capacity as well as the inflating pressure will be agreed between the car and tyre manufacturers. However, this approval does not necessarily apply to tyres which are specially produced for the US market and which bear the additional marking ‘P’
For tyres with speed symbols ‘R’ to ‘V’ and standard road tyres the minimum pressures set out in the tables and corresponding with load capacities are valid up to 160 km h-1 .
Special operating conditions, the design of the vehicle or wheel suspension and expected handling properties can all be reasons for higher pressure specification by the vehicle manufacturer.
Further, for speeds up to 210 km h-1 the linear increase of basic pressure has to be by 0.3 bar (i.e. by 0.1 bar per Dv ¼ 17 km h-1) and at speeds above 210 km h-1 the tyre load capacity has to be reduced in accordance with item 10.1.2.6.1. If the tyre load is lower than the maximum load capacity, a lower additional safety pressure can be used in consultation with the tyre
manufacturer.
For tyres with the speed symbol ‘W’, the pressures apply up to 190 km-1. After this it has to be increased by 0.1 bar for every 10 kmh-1 up to 240 km h-1. For higher speeds, the load capacity must be reduced.