Originally Posted by Altis
The difference is that those genuine parts weren't for your car... they don't tend to warranty modifications like that.
The original factory bumper to bumper warranty on the car itself as relating to brakes is void yes... BUT...
The replaced parts themselves are going to have a warranty against defects in materials and workmanship as long as they are installed correctly on the car they are designed to be installed on and the system is complete and the model in question has the brakes available as an option.. (a Ford Focus in this case, whether the car originally had drums or not).. they are warranted to work correctly. And all ford service work is warrantied to be free from defects in workmanship of the installers... so if the parts fail due to a flaw in the parts themselves, or due to an incorrect installation by the dealer.. that would be covered.. for x number of months/year(s) or so many thousand miles.. from the date they were installed...
Now if the focus didnt have rear discs available on any model for a given year, and parts from another similar vehicle were used.. they probably wont warranty that.. and tell you it might or might not work and its at your own risk.
Now if you happen to take your wheels off and bust a chunk of the rotor off with a 3 lb sledge hammer... they're probably not gonna cover it..