[flameout]

Okay, so it sounds like they won't wear too fast (we won't run on asphalt bad enough to cause horrible control issues).

However, since it sounds like we'll have to replace them about once per year, do people have recommendations for how to replace the rollers? AndyMark sells them for $3-4 apiece, which is too much for us to spend each year (we have no problem buying replacements -- I would like to get the yearly maintenance cost down to $20 or less, which necessitates cheap roller replacements).

We've talked about fashioning rollers out of PVC ourselves, but I fear that it is too slick, negating the mecanum effect (by sliding just as easily along the axis of rotation as it rotates around that axis). Is there a less expensive way for us to make our own rollers (I know other teams have used urethane, but I recall that being above our budget)?

It sounds like the best option would be to buy a set of AM mecanums (or other COTS mecanums) and replace the rollers with something cheaper than AM's rollers each year -- does anyone disagree?