Outside of the US, most car companies still provide alternate pressure depending on vehicle load and maximum expected substained speed. I think the uS single pressure number is a result of CAFE rules. When they run the CAFE tests they adjust the pressure as specified. If the secifications allowed for a lower pressure, that is what would be used. So instead of a set of recommendations based on anticipated operating conditions, we get a one number fits all recommendation. This number is almost certainly on thehigh end of the acceptable range since it has to work for maximum loads and maximum US speeds (probably 85 - 90). Michelin does recommend increasing pressure for substained high speed driving. Here is a statement from the Harmony tire line specs:
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 160 km-h (100 mph), load and inflation must be adjusted according to the table below.
S-Speed Rated Sizes: Maximum Speed (mph) 100 106 112 Inflation Increase (psi) 0.0 1.0 2.0 Load Capacity (% of max.) 100 100 100
T-Speed Rated Sizes: Maximum Speed (mph) 100 106 112 118 Inflation Increase (psi) 0.0 1.0 2.0 3.0 Load Capacity (% of max.) 100 100 100 100
Ed
