Aero push is a car going tight in another car's turbulent wake — the leading car strips downforce off the car behind, so the trailing car won't turn and pushes up the racetrack. Clean air cures it.
The tell is the condition, not the corner: a car tight only behind somebody and fine by itself has an air problem, not a setup problem. Daily Downforce defines dirty air as “the turbulent airflow behind a car” that “does not allow the aerodynamics of the trailing car to work properly through the turns,” and names the result: “the behind ends up ‘Pushing’ up the track in what they call an ‘Aero push.’” How much reaches grassroots racing is genuinely argued. Nobody disputes it at high-speed asphalt pace. At a Saturday-night dirt track it competes with plainer explanations — a torn-up lane, dirt off the leader’s tires, or simply following a slower car — and no published numbers settle it. Move your line before you move the chassis.
A car that is only tight in traffic does not need a setup change, and making one anyway ruins a car that was good in clean air.