A cushion is considered dead when the reaction of a ball off the rubber is less than perfect. The speed off the rail is noticeably slower and at a more direct angle out then when the ball went in.
A dead rail absorbs ball energy like a sponge. Sometimes you also hear an extra rapping sound because the rubber slaps against the wood part of the rail. A cushion only works well when the rubber is forced tightly up against the wood support.
Causes for dead rails can be:
The cushion has separated from the wood support (usually only in small areas of a few inches wide). The small strip of wood that forces the rubber against the cushion could have disintegrated.
The rubber has hardened or softened - usually from age or because it was cheaply made.
Generally, if the affect is minor, you just play around the dead areas and continue your game. However, if the affect is widespread across a rail, it should be fixed. Playing on a table with dead cushions can make your pool playing experience less than enjoyable.
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