Tire load index tells you how much weight your tire can safely carry. During the process of switching tire sizes, try to always use tires with same or greater tire load index than the original equipment tires. Try to never overload your tires more than the maximum weight that is relative to your tire load index. Overloading can cause tire blowout, tire damage or uneven tire wear.
Some tires may have dual load index, with second number indicating tire load index when used in dual rear tire set.
Check tire load range chart for tire load ranges and their defined maximum tire inflation.