[sanddrag]

If you need something that comes with a keyway already all that I know of are these http://www.npcrobotics.com/products/...at=22&mode=gfx They are a little heavy but you might be able to lighten them a little by drilling or something.

And then there are Skyway Wheels http://www.skywaytuffwheels.com. You will have to call them to see exactly what they can give you with a keyway hub for a relatively low price. Tell them you are with a FIRST team and you are working on a special project. The selection depends on what kind of production runs they currently have going because they don't normally offer every wheel with every kind of hub (and a keyway hub is one of the lesser common ones for them). Most likely, they will either be able to offer you a BeadLOK wheel with foam-rubber tread or a 4" universal wheel for a pneumatic or urethane tire.

The foam-rubber tread on the BeadLOK wheels has terrible traction unless you turn them down to flat on a lathe like the wheel in this picture http://www.firstrobotics.uwaterloo.c...etrains001.jpg And even then, they will rip to shreads on a surface like concrete or asphalt. They are good on carpet though. What kind of surface will your robot be operating on?

Also ,you can always add some sort of traction enhancing material to the surface of your wheels like McMaster Incline Conveyor Belting.