12 mm Thru-Axle Chain Keeper Dummy Hub
A dummy rear hub that clamps between the dropouts of a 12 x 142 mm thru-axle frame so the chain stays taut and the derailleur stays put while the rear wheel is out for washing, chain cleaning or car transport. The 142 mm long body has a 12.5 mm bore for the 12 mm axle, 24 mm end caps that bear on the dropout faces, and a captured print-in-place roller (33 mm OD, 8 mm wide groove floor, 45 degree flanges) centred 25 mm from the drive-side face to sit near the cassette chain line; two snap-off 3 mm spacer rings bring it to 148 mm for Boost frames. Print standing on its end cap and put a dab of grease in the roller.
tool bike thru-axle chain-keeper