Is your C4 plagued by body flex when you remove the top? This is a common complaint from most C4 owners. Cornering can feel rather uncomfortable with the top removed since the top provides a substantial amount of rigidity to the chassis. Unkempt roadways also cause problems that will eventually lead to squeaks and rattles.
The top is an integral component that helps to stiffen the chassis. When the top is removed the frame no longer is reinforced because the only frame member is below the doors. The door striker is the only other component that could be considered a source of reinforcement, but being such a small item, the support it offers is negligible.
Unfortunately, this lack of support leads to frame and body flexing which translates to ineffective cornering. It also begins to weaken the chassis as a unit. This became very evident in late 1986 when convertibles were introduced. As a result, all C4 convertibles were equipped with an underbody “X” brace. (more…)