When the rain arrives mid-race, the bike changes and the clock does not stop. Here is what the twenty seconds in the pit box actually contain.
A flag-to-flag race is declared when conditions change enough that the tyre on the bike is the wrong one, but not so much that the race has to be stopped. The rider keeps racing; the second machine, already built to the wet spec, waits on its stands.
The swap itself is a dismount, eight metres on foot, a remount and a launch — a pit lane that costs upwards of twenty seconds even when nothing goes wrong. The decision of which lap to take is worth more than the swap is: come in a lap early on a drying track and the tyre is dead by the flag.
Sepang is the circuit that produces them most often. A tropical afternoon can put standing water on half the lap and leave the other half dry.
