Product and engineering tend to take center stage at the Frankfurt International Motor Show, but management shakeups at two prominent German suppliers also were gaining attention this year.

Tire producer Continental AG, which owns brake manufacturer Continental Teves, loses Stephan Kessel, 47, as chairman of the executive board.

Although the company says he departs “on very amicable terms,” sources say Mr. Kessel left over a disagreement about what to do with Continental's ContiTech Group, which sells non-tire rubber products. The group was up for sale but later taken off the market. Mr. Kessel wanted to further pursue a sale of the unit.

His replacement is Manfred Wennemer, 53, who has been with Continental for seven years and since 1998 has headed the ContiTech Group.

Wolfgang Ziebart, 51, who left BMW AG a year ago to head Continental's Automotive Systems Div., also gains additional responsibilities for technology development as deputy chairman of the company's executive board.

Mr. Ziebart says that under Mr. Kessel's leadership, Continental was considering some major acquisitions, and that Mr. Kessel's growth strategy may have been too ambitious.

At Kolbenschmidt Pierburg AG, Dieter Seipler, 54, departs as executive board chairman, effective Oct. 31, to become president and chief executive officer of another automotive supplier, Filterwerk Mann+Hummel GmbH. Mr. Seipler had been Kolbenschmidt Pierburg chief executive since 1998.

Replacing him at KP is Gerd Kleinert, 53, who has been chief executive of KP's sibling company, Aditron AG, an electronics producer. Previously, he had been vice president and general manager at TRW Automotive Electronics.

Mr. Kleinert will have a seat on KP's five-member executive board. He began his career as a toolmaker at General Motors Corp.'s assembly plant in Russelsheim, Germany.