Up here in NH and ME, they get well into the 50s, with occaisional big ones over 60. They are powerful predators, and very intelligent pack hunters.
My dad came across a bull moose kill up in Northern ME a few years ago snowmobiling. The coyotes got a big healthy bull moose in between two ridges, with fairly deep snow. Then, they just worked him back and forth in the valley between the ridges. When he got to the other end, they would turn him and run him back again. The ridges were really steep, and with the snow, the moose did not try to go uphill to escape. They just kept working him until he apparently became exhausted, and then they pulled him down. He appeared to have been quite large and healthy.
Watching the tracks told the story. The coyotes moved in a straight line, with the lead animal breaking trail. Every so often, there would be a place where one stepped to the side and then back into the track again. My dad reported the kill to one of the state biologists, and described the tracks. The biologist confirmed that the lead animal breaks trail until he/she is tired, then steps aside to allow the pack to pass, and steps in at the end to rest. That way, a fresh animal is always breaking trail, and the tiredest ones are at the back of the pack where the going is the easiest.