The problem with sideways creep has been probably the biggest problem since the start of WC3D. It is due to the fact that the WC3D is limited to FixedUpdate() tick rate and it works on physics-based formula which essentially creates a reactive force for any amount of slip that happens. A too small force will cause slip and a too large force will cause jitter / jumping and as such the force must never be larger than required. Default wheel collider has this problem too to some extent but it can be partially solved by increasing the update substep on the wheel itself (which is possible because default wheel is calculated in the PhysX itself), while the WC3D can not do that because it is bound to the FixedUpdate(). I am at the moment testing out some ideas but while improvements in that field will happen, I can never garantee that the vehicle will be able to be glued to the place on the sloped surface - as long as rigidbody and AddForceAtPosition() are used. Even the constraint option of rigidbody and the default wheel collider will creep over time. Hope this answers the question.