We had these hubs made to trim off a valuable 3.8mm (.15") by making the set-screw hole on the aluminum rim, underneath the tire. It means you have to remove the tire from the hub to tighten it, but well worth it for designs that need every millimeter of room! they come with a generously thick rubber tire for maximum traction Ideal for minisumo, like our 1st place finishing Strong Bad! The tire mounted on the hub measures in at 31.2mm (1.23in) diameter and overall width of 13.2mm (0.52in) wide. The hub is drilled for a 3mm axle ideal for the GM12a-14a series of gear motors! It's a nice, fat, beefy wheel ideal for small robots! Secure it to your motor shaft with the included 4-40 hex grub/setscrew. Requires 0.050 hex wrench, like our HexW050. Although you can simply install the motor from the outside, we designed it so you could be mounted internally to the hub. We've found that the internal cutout came back from manufacture a wee bit thick, but a bit of filing on the edges of the GM12a lets it fit right in. By hand-filing the edges down, you can fine-tune the installation so the brass edges of the gearbox act as alignment bushing points that assist in keeping the wheel spinning true. Or, use a Sherline lathe to remove 0.010 from the ID of the cut-out! Wheels each include a hub, a tire and grub screw. The entire wheel assembly weighs 12 grams.

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