The Z-SupportBracketR and Z-SupportBracketL support the gantry weight and eliminate the axial force on the Z-Motor.

Update
The Z-Support Bracket can be also used as a Radial Guide (x and y). I uploaded a ring for this purpose.

The Z-Axis Wobble Absorber http://www.thingiverse.com/thing:42260 or a similar solution is recommended in combination with the Z Support Bracket.

The Bearing Ring is split into 2 pieces in order to avoid printing with support material.

1. Insert the Bearing into the Ring.
2. Put the Ring with the Bearing into the Z-Support Bracket.

BOM for both Support Brackets:

2x Stainless Threaded Rod M8 x 1.25 mm x 320mm long (the original ones are to short and must be replaced).
2x Bearing 608ZZ or similar: inside dia 8mm, outside dia 22mm.
2x 8mm Washer.
2x Hex Nut M8 Nylon Locking.
2x Spacer i-dia 8mm, o-dia min 10mm, x mm long (the length depends on your Z-Coupling).
4x (Hex) Screw M5 x 12mm.
4x 5mm Washer.
4x Misumi M5 T-Slot Nut.