Kettler SPRINTER 1.1 Instructions De Montage Et D'utilisation page 36

Band tightening
Turn the adjusting screw (picture below) max. one turn clockwise. Repeat the process on the other side. Check whether the endless belt
is slipping. If this is the case, you must carry out the described procedure again. Be very careful when adjusting and tightening the belt;
extreme over- or under-tensioning can damage the treadmill!
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