to bisecting plane 40 and below second axle plane 86 second casters 182 may be pivotable about a respective second pivot axis 184 and rotatable about a respective second rotation axis 186 second casters 182 of third wheel set 180 each define upper and lower second caster tangent points 188 190 on a circumference thereof lower second caster tangent point 190 is distal from second axle plane 86 relative to upper second caster tangent point 188 and is contained in a second lower tangent plane 192 that is perpendicular to bisecting plane 40 and extends parallel to and between second axle plane 86 and first lower tangent plane 122 therefore the positioning of third wheel set 180 with the configuration of second casters 182 resulting in a second lower tangent plane 192 above first lower tangent plane 122 permits the pivoting characteristic of mobility chair 10 as described above in one embodiment second casters 182 may be secured to frame 112 by second caster brackets 194 second casters 182 may possess a wheel diameter dimension u201c n u201d of between about 0 5 3 inches such as about 1 inch second casters 182 do not touch the floor during normal movement of the chair except when it is tipped forward giving the child the ability to reach things on the floor these can be adjusted to.