The maximum recommended compression of a Rubber Belt is 25% of its current thickness. This is generally sufficient even for heavy weight fabrics like denim that require 14-16% shrinkage. Compression in excess of this recommended amount results in additional stress on the Rubber Belt and may result in premature failure, including cracking.
Make sure that the compression plate (gauge) is set correctly as described in calibration of compression plate. This is especially important when installing a new Belt and after each grinding operation. An incorrect and faulty setting can result in too much compression on the Rubber Belt.