Yeah Ding, the beam does help turn in and front end grip as our foreign friend has stated.

When a standard beam-ed cossie turns into (lets say) a right hand corner, as the car rolls into the corner the geometry of a standard cossie rear beam, actually makes the outside wheel (left hand wheel) steer right as well. Therefore fighting the front and pushing the front on.

The rear beam virtually eliminates this compression steering effect and allows the rears to simply follow the fronts and not fight against them. We also set up the rear with less toe in to aid turn in. This can get hairy though as not enough rear toe in will produce a very twitchy car.