How to Make It
Smash garlic cloves with flat side of a chef’s knife on a cutting board. Sprinkle with salt; smash again, pressing salt into garlic to create a rough paste. Transfer garlic paste to a small bowl; whisk in oil and vinegar. Cover and refrigerate basting liquid at least 24 hours or up to 5 days.
Stir together all spice rub ingredients in a small bowl, and set aside.
Place tri-tips in a large metal bowl. Baste evenly with 1/4 cup basting liquid, reserving remaining basting liquid. Sprinkle meat evenly with one-third of the spice rub (Reserve remaining spice rub for another use. Store in an airtight container at room temperature up to 1 month.) Refrigerate tri-tips, uncovered, 1 hour and 30 minutes. Remove from refrigerator; let stand at room temperature 30 minutes.
Open bottom vent of a charcoal grill completely. Light charcoal chimney starter filled with briquettes. When briquettes are covered with gray ash, pour them onto bottom grate of grill, and push to one side of the grill. Adjust vents as needed to maintain an internal temperature of 400°F to 450°F. Coat top grate with oil; place on grill. (If using a gas grill, preheat to medium-high [400°F to 450°F] on one side.) Alternatively, prepare an oak wood fire on a Santa Maria grill.
Place tri-tips on oiled grates over side of grill with coals (or lit side of gas grill). Grill, uncovered, until lightly charred on both sides, 2 to 3 minutes per side. Move tri-tips to side without coals (or unlit side of gas grill). Grill, uncovered, until a thermometer inserted in thickest portion of meat registers 130°F, 30 to 35 minutes, flipping and basting meat with reserved basting liquid every 5 minutes.
Remove tri-tips from grill, and cover loosely with aluminum foil. Let rest 15 minutes. Thinly slice meat against the grain. Serve with tomato salsa and pinquito beans.