Pears should be harvested when fully formed, but not ripe. Most years that time is early August for Bartletts, but this year everything seems to be early, so it's important to watch your pears for when they are mature.
How do I know when my pears are ready to pick?
The best way to tell if a pear is ready to harvest is by taking the fruit in your hand and tilting it horizontally. The mature fruit will easily come away from the branch at this angle (as opposed to its natural vertical hanging position). If it is not yet ready for picking, it will hold on to the branch.
Will pears ripen after you pick them off the tree?
How Pears Ripen: Unlike other fruit, pears do NOT ripen properly when left on the tree. They are one of the only fruits that must be picked unripe and allowed to ripen off the tree. If left on the tree, a pear will over-ripen from the inside out and the center will be mush and rotten before the outside gets soft.