In the late 1990s, Firestone tires installed on Ford Explorer SUVs had a high incidence of failure. Lawsuits were filed against Firestone and Ford (defendants) to recover damages based on either: (1) the injuries or deaths caused by the defective tires or (2) the risk of failure, including damages for diminished resale value or mental stress. Lawsuits that had been filed in federal court were transferred to the United States District Court for the Southern District of Indiana for consolidated pretrial proceedings, after which they would be transferred back to their respective courts. Some plaintiffs sought to avoid having their cases transferred back. These plaintiffs brought a new, consolidated federal suit in Indianapolis and sought class certification. The judge certified two nationwide classes. The first covered those who owned or leased a Ford Explorer during the relevant period (the Explorer class). The second covered those who owned or leased certain types of Firestone tires during the relevant period (the tire class). These classes together covered over 60 million tires and 3 million vehicles. In certifying the two classes, the district judge ruled that, under Indiana’s choice-of-law provisions, the law of the place where the defendants had their headquarters governed. Accordingly, the district judge ruled that Michigan law would govern the Explorer class claims and Tennessee law would govern the tire class claims. Ford and Firestone sought interlocutory review.