In 1964, he was elected mayor of Bruchsal. His main achievements were the reconstruction of the chateau of Bruchsal (which had been destroyed in 1945), the merge of 5 smaller towns surrounding Bruchsal, and the redesign of the City-Centre of Bruchsal in the 1980s (which had started in the 1970s and was completed by his successor Bernd Doll).
Bieringer started to engage for environment protection which was one of his last topics before he had to stop work due to serious illness at the end of 1987. He died in February 1988.