Time trials was scheduled for five days. The minimum speed to qualify was set at 115 mph. In the months leading up to the race, several top drivers that were members of a union, the American Society of Professional Auto Racing (ASPAR), threatened to boycott the race over the purse size. The AAA Contest Board refused to heed their demands, and when the entry list was closed on May 8, many of the top drivers, particularly several popular west coast drivers, were not on the list. A total of 35 cars were entered, but at least nine had no driver listed, and 13 of the entries were inexperienced novice drivers. After the practice began for the month, officials decreed that the boycotting drivers would not be allowed late entry. After several weeks of dispute, an agreement was made for the ASPAR drivers to participate midway through the month.