[MrForbes]

Also it will help us help you if you give a complete description of your drivetrain/chassis....ratios, width, wheelbase, number of wheels, tread type, whether the center wheels are lower than the end wheels and by how much, etc.

Long, narrow, 4 wheel robots with sticky tread, and not much final drive reduction, just don't turn easily. Wide, short, 6 wheel bots with lowered center wheels, not so aggressive tread, and more final reduction turn just fine in high gear.