To alleviate poor shifting and uneven drive train wear most manufacturers recommend chain replacement at or before 1 stretch a 1 of wear is enough to affect chainrings and sprockets and allow shifting performance to deteriorate now you can quickly and accurately determine the wear and stretch of any chain with the park tool cc2 chain checker simply insert the chain checkerrsquos pins into two links press the swing arm gauge tight and then check the gauge window for an accurate reading