Kyle Busch began Sunday's AAA 400 Drive for Autism in the pole position, but a loose wheel caused him to fall back and his No. 18 car eventually finished 16th at Dover.
NASCAR senior VP of competition Scott Miller said Monday that Busch's loose wheel was a result of human error, and the No. 18 pit crew was penalized Wednesday for the safety violation.
NASCAR rules mandate a four-race suspension for crew chief Adam Stevens, tire changer Jacob Seminara and tire carrier Kenneth Barber after a tire came loose from the Joe Gibbs Racing Toyota.
Busch’s pit crew appeared to drop the jack before the lug nuts were secure on the left rear tire during a scheduled pit stop, causing the tire to come off on the track after Busch had left pit road.
NASCAR implemented improper-installation rules and penalties for safety reasons, to prevent teams from saving time by leaving lug nuts loose in order to gain track position.
NASCAR also penalized the No. 29 Camping World Truck Series team of Chase Briscoe for a similar infraction in which a tire came off during Friday’s event at Dover. JGR's Xfinity Series No. 19 crew chief Matt Beckman was also fined $5,000 for a violation related to improperly installed lug nuts.