When to harvest pears

Hi I'm new to the site and this has probably been asked before.  I have two pear trees (comise and conference) on smallroot stock. Last year I had small pears which I didn't bother picking. This year they have very large fruit on them and are weighing down the branches.  I read somewhere that pears should be harvested before they are ripe. Is this correct or do I leave them on the trees until they ripen. All advice welcome.

Thanks for your advice.  Making perry sounds like a good idea!!