Simplify the following text for a Grade 6 native English-speaking person.
Original: In some cases the axle may be fixed in position with a bearing or bushing sitting inside the hole in the wheel or gear to allow the wheel or gear to rotate around the axle . In other cases the wheel or gear may be fixed to the axle , with bearings or bushings provided at the mounting points where the axle is supported .
Simplified: A tag axle is a dead axle situated behind a drive axle .