Make the Syrup
In a large jar with a tight-fitting lid, vigorously shake sugar, chopped ginger and water until the sugar dissolves, about 1 minute. Strain into a pitcher.
Mix the Drink
Add tequila, orange liqueur, 1 cup lime juice and pear juice to the pitcher; stir.
Rim the Glass
Pour 2 tbsp. lime juice on a plate. Spread sugar and ground ginger on another plate. Dip the rims of 8 glasses into the lime juice, then into the sugar and ginger
Fill the glasses with ice, then add the margarita. Garnish with a large slice of crystallized ginger.