Many platform and clipless pedals can be serviced. Usually there is a dust cap at the outside end of the spindle that can be unthreaded or pried out and the bearings are either cartridge-type roller or ball or they are cup-and-cone. For the cup-and-cone types, the problem is working in the very narrow channel the spindle and bearings are in. Usually a very thin wall socket is needed for the adjustments and to tighten the locknut.