clock (someone or something) at (a certain speed)
To track the speed at which someone or something moves. (The speed is stated after "at.") You're getting a ticket because I clocked you at 90 miles an hour—and the speed limit here is only 55.
clock someone or something at something
to measure the speed of someone or something to be a certain figure. I clocked the runner at a record speed for the race. Karen clocked the race at three minutes flat.