During my experience with FIRST, I have observed teams using several different wheels for their drive trains. One thing I have noticed is that teams with mecanum wheels generally choose large diameter wheels (8" or above) while teams with non-mecanum wheels choose generally smaller wheels (4"-6"). I am wondering what the reasoning behind this is. Obviously if you can get the same angular velocity on a larger diameter wheel, then that results in a greater linear velocity of the robot but besides that, I don't understand the advantages of choosing larger wheels, specifically the reason for not choosing the 6" versions offered by
Andymark and
Vex. Does the size increase improve the mecanum's performance in some way? Do smaller mecanum wheels have a greater tendency to break?
What Delphi says doesn't matter. What the official Q&A says matters. - Tetraman [more] 
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