Inflation pressure increase must not exceed the maximum pressure branded on the tire sidewall. When a customer requests a replacement tire with a lower speed rating than the original equipment tire, you must clearly communicate to him or her that the handling of the vehicle may be different, and that its maximum speed capability is limited to that of the lowest speed-rated tire on the vehicle. Exceeding the lawful speed limit is neither recommended nor endorsed.

For high-speed driving, additional inflation pressure and possibly reduced tire loading and/or upsizing is required. In the absence of specific recommendations by the vehicle manufacturer, use the following guidelines based on those in the European Tyre and Rim Technical Organization Standards Manual.

For speeds over 160km/h (100 mph), load and inflation must be adjusted according to the table below.

H-Speed Rated Sizes:
Maximum Speed (mph) 100 106 112 118 124 130
Inflation Increase (psi) 0.0 1.0 2.0 3.0 4.0 5.0
Load Capacity (% of max.) 100 100 100 100 100 100

V-Speed Rated Sizes:
Maximum Speed (mph) 100 106 112 118 124 130 136 143 149
Inflation Increase (psi) 0 1 2 3 4 5 5 5 5
Load Capacity (% of max) 100 100 100 100 100 100 97 94 91

W-Speed Rated Sizes:
Maximum Speed (mph) 118 124 130 136 143 149 155 161 168
Inflation Increase (psi) 0 1.5 3.0 4.5 6.0 7.5 7.5 7.5 7.5
Load Capacity (% of max) 100 100 100 100 100 100 95 90 85

Y-Speed Rated Sizes:
Maximum Speed (mph) 118 124 130 136 143 149 155 161 168 174 180 186
Inflation Increase (psi) 0 0 0 0 1.5 3 4.5 6 7.5 7.5 7.5 7.5
Load Capacity (% of max) 100 100 100 100 100 100 100 100 100 95 90 85

courtesy of BFGoodrich tires