 Complete the following phrase:  Disagreement between the teams and the sports administrators over the technical regulations for the 1981 Formula One season contributed to Goodyears temporary withdrawal from Formula One and meant that the 1981 South African Grand Prix was run by the teams to 1980 regulations using cars with sliding skirts. Piquet finished second in a BT49B, but the race did not count towards the championship. The season proper opened with the United States Grand Prix West, at which the BT49C was introduced. To the teams surprise, it was the only car to exploit the obvious loophole in the new ground clearance regulation by lowering itself, but the BT49Cs raced with conventional suspension after the hydropneumatic system repeatedly jammed. The team revised the system continuously over the next three races and used it to set pole position at the Brazilian and Argentine Grands Prix and win the Argentine and 