Unity 5 wheelcolliders dont collide boxes

Hi there. Im developing some truck sim game, with offroad elements, and now, im stuck. Unity anounced new wheelcolliders without that big array of problems of older versions of engine. Now, when i have rebuild project for U5, I expected, that wheelcolliders will collide objects right. But them dont. When i driving on some box collider, car starts to jump, when car must slowly go upper or down. What can i do with that bug?
PS - i know that wheelcollider works on the raycast of y axis, but maybe i dont know something gonna help me? Thanks for the answers