Postby lighthammer » May 15th, 2014, 10:00 am
ARB and Ironman bumpers are designed to bolt onto the crush-zones of the chassis and they're designed to retain the functionality of the airbag sensors. If you look on the ARB website or any information regarding ARB/Ironman bumpers, they make that statement clear (this is a requirement of Australian law where the bumpers are made). Even the mounting brackets are designed to mimic the purposes of factory mounts in case of frontal collision.
Those steel bumpers were actually originally designed to deflect kangaroo hits while driving at high speed on outback desert roads in australia (true story!). so anything under 120kg (the size of an adult male bull kangaroo) will easily be deflected. A large 2-ton vehicle is a different story, at that point the bumper will act the same as a regular factory bumper. (the weight will exceed the bumpers tensile strength limit and it will deform similarly to a plastic bumper).
DIY and homemade bumpers may be a different story, it depends more on the fabricator/installer and how strong they design it. If they designed it to withstand massive shock, eg. robbing a bank and stealing a safe in Rio, Brazil, then it's a different kettle of fish.
Either way, when it comes to a 3900lb truck/suv vs. 2900lb car, the heavier vehicle usually wins.