[EricH]

Originally Posted by Ether

Half?? Wow, you must have been watching some bots with pretty beat-up wheels.

Quality mecanum wheels will have nearly equal forward and strafe speed, but they are very expensive. If they get hit and damaged so that the rollers don't spin freely under load, you'll start to see degradation in sideways speed.

Or if the rollers too tight, or are rubbing hard against the sideplates. Either of those will cause it. This is another of those cases where theory says one thing, and reality says to theory, "You need to come over to MY place tonight!" Just about every mecanum robot I've seen in FIRST is slower sideways than front-back. 357, 330's testbed, and many others. It's faster than 1/2 speed, but it's nowhere near full speed. Maybe about 3/4 speed.

That's just what I've seen at competitions; the root causes could be any of the ones we've mentioned, or something we haven't thought of.