For the best results, use the best-quality in-season sweet corn you can find. If you'd like to use wood chunks instead of wood chips when using a charcoal grill, substitute one 3-inch wood chunk for the wood chip packet.

Using large piece of heavy-duty aluminum foil, wrap chips in 8 by 4½-inch foil packet. (Make sure chips do not poke holes in sides or bottom of packet.) Cut 2 evenly spaced 2-inch slits in top of packet.

FOR A CHARCOAL GRILL: Open bottom vent completely. Light large chimney starter three-quarters filled with charcoal briquettes (4½ quarts). When top coals are partially covered with ash, pour evenly over half of grill. Place wood chip packet on coals. Set cooking grate in place, cover, and open lid vent completely. Heat grill until hot and wood chips are smoking, about 5 minutes.

FOR A GAS GRILL: Remove cooking grate and place wood chip packet directly on primary burner. Set grate in place; turn all burners to high; cover; and heat grill until hot and wood chips are smoking, about 15 minutes. Leave primary burner on medium-high and turn off other burner(s). (Adjust primary burner as needed to maintain grill temperature between 300 and 350 degrees.)

While grill is heating, combine mayonnaise, vinegar, sugar, ½ teaspoon salt, pepper, horseradish, and cayenne in medium bowl. Brush corn with half of mayonnaise mixture. Sprinkle corn evenly with remaining 1½ teaspoons salt.

Clean and oil cooking grate. Arrange corn on cooler side of grill. Cover, placing lid vent over corn on charcoal grill, and cook until corn is tender and color has deepened, 16 to 18 minutes, turning corn once halfway through cooking. Move corn to hotter side of grill and cook, uncovered, turning occasionally, until spotty brown all over, 5 to 6 minutes.

Transfer corn to serving platter. Brush with remaining mayonnaise mixture. Serve.