With a ban on high-mounted wings following Graham Hill and Jochen Rindt's accidents in the 1969 Spanish Grand Prix meaning low grip was more of a problem than ever the 63s were pressed into service two races later at Zandvoort. Hill tried the car in the first qualifying session, but after going nearly four seconds quicker in his regular 49B, and declaring the 63 a "death trap", it was left to Lotus test driver John Miles to give the car its debut at the French GP, retiring after a single lap with a fuel pump failure. At the British Grand Prix both chassis were available, but after Hill again tried the car in practice, and again refused to drive it, Jo Bonnier drove the car with Hill in Bonnier's 49B, while Miles again drove the other 63. Bonnier retired with an engine problem while Miles finished tenth, some nine laps down.