McLaren are asking Fernando Alonso and Jenson Button to leave their visor tear-offs in the cockpit rather than discarding them onto the circuit, because it could cause a brake-by-wire failure.
According to Auto Motor Und Sport, the team nearly suffered a similar failure as Spain on Alonso’s car in Hungary when one of the visor tear-offs the drivers keep on their helmets got caught in the rear brake ducts of his car, which caused them to overheat. In those instances the brake-by-wire system fails and sends all of the braking energy to the front of the car – much to the surprise of his mechanics when he came into the pits to retire.
Apparently the same thing happened during the Hungarian GP, but because of the Safety Car McLaren were able to stop the brake-by-wire failure again by getting rid of it during the pit lane pass through.
The team have traced the issues back to their extreme size-zero aero package at the rear, and are looking at introducing new parts that may help stop the problem from occurring. Alternatively they could take up Damon Hill’s suggestion of giving their drivers a bin in the cockpit, so they can discard all of their rubbish into there rather than littering the circuit.