What was installed along with the Big Brakes? Did the control arms have to be removed and or modified? Does it use the factory spindle assembly or does the kit come with new spindles?
If the tires did not have a problem prior to the retrofit than one can only conclude something happened during the installation. Do you have an MB dealer close to you? If so they should be outfitted with the new Beisbarth alignment system and with the right person operating the equipment they should be able to determine the fault.