You should be looking at the cause. If the carbon part of the brush is more than 1/4 of an inch long, the problem may be a worn armature, requiring a replacement motor. There may be other problems. Fit new brushes and check after 1 or 2 months. If they are burnt your problem isn't with the brushes. Fitting the wrong brushes can also be problematic. Some look the same, maybe a different coulored housing but they are different. Some are laminated. Basically, some are harder than others. Fitting a brush that is too hard will wear the armature. Fitting brushes that are too soft will wear and clog up. The heating is caused by 'arcing', where a small air gap, just for a split second, between the brush and armature causes the voltage to jump the gap and 'arc'. Basically, doing a small, perhaps microscopic weld. These add up until the armature is no longer round, adding to the problem. Brushes should be changed every 12 months, regardless. Hope this is helpful. If you want, contact at at profhig@breathe.com
Paul Higgins, July 2005