[Clan]

Originally Posted by Quacker

The original beam is designed to deform, augmented by the crush cans, in order to absorb the energy and minimise its transfer to the people inside the car. The non-deformable part is the safety cage that surrounds the passenger compartment.

Removing the rear deformable energy absorbing units and replacing them with a very strong and rigid tow bar does not compromise the safety cage at all. Indeed it probably strengthens it. At the expense of not dissipating the energy that the original design does. A rear end shunt will be felt much harder, although all the active safety features, like seatbelt pre-tensioning, pre-crash brake actuation and hazard warning activation should all work perfectly and the safety cage should work at least as well as without a hitch.

Energy absorption is not entirely lost when the hitch is fitted, because the mounting pads on the chassis [where the original crush cans were bolted on and also the hitch frame] are also somewhat crushable and the round hitch cross bar is welded at that point to the pad extensions only at the back, with a small void in front. This is not some artistic license by the designers. It is to make a joint that will fail under a specific impact force with the void allowing the weld to stretch and dissipate some energy as it does so. No way can it be as effective as an extruded aluminium box profile mounted to deep crush cans of course, but I'm sure they have done their best commensurate with the durability and strength constraints of integrating a drawbar capable of long term integrity with pulling, pushing, twisting and lateral loads that comes with towing two tons with probably a four times overload/failure safety factor.

the New xc90 towbar has a lazer cut slot cut in the main mounting bracket each side to give presumably the same impact absorbing quality as the removed beam .