[pryoplasm]

it might be helped if you also describe how you are turning it. if you have 2 joysticks for each of the sides for tank drive, are you moving one back on the y axis, while moving the other forward on the y axis?

our team had a similar problem a while back, and what helped was with the drivers, instead of full forward and full backwards on both sticks, alternate the sticks, going one forward, and the other backwards, it will be a slightly slower turn, but it might help.