[EricH]

Originally Posted by the man

Why are your middle wheels lower?

Standard 6WD trick to keep maneuverability. It shortens the wheelbase, making turning easier.

But 3/4" of an inch is WAY too much for a standard 6WD drop. Those are more often in the 3/16" range. With 3/4" inch, there's a little bit of a tipping worry even when you aren't crossing the rail--all it takes is a hard bumper hit when you're rocking while in acceleration, and your robot is no longer on its wheels.