Quote:
Originally Posted by RRW.Michael
This is correct, it costs tens of thousands to get products tested for DOT approval. What we're looking into doing is virtual impact testing, which doesn't give the product DOT approval, but does give us accurate information on how the bumpers will act in the event of an incident. That testing, along with our experienced engineering department, gives us the ability to create a sturdy product that will work as expected. With all metal bumpers, the sensitivity of airbag deployment is a bit more sensitive, as there's no more foam cushion behind a plastic bumper. But that's not saying small taps will set it off, I've personally pushed open gates and moved stuff around with my bumpers with no incident. In an accident, the airbags will still deploy as the sensors aren't modified or moved in any way.
As you mentioned, just about all brands aside from ARB don't do the crash testing for DOT approval, and market their bumpers as "offroad use only". We're going to go the extra step with virtual testing, to get insight on how the design does, and how to improve it to best protect the car in the case of an incident.
Edit: Some more info on the 4Runner airbag system:
The factory bumpers have a foam pad behind the plastic bumper exterior, which prevents impacts of 5mph or slower from transferring the force of impact into the crash bar, which then could shift back and set off the airbag sensors. With an aftermarket bumper, you're pretty much replacing your crash bar with a whole bumper, so all that changes is the loss of the foam pad. So from that deduction, the difference with an aftermarket bumper would change the front airbag sensitivity from 12-18mph with a fixed non-deforming wall to 7-13mph. So if you're offroad, and smash into a rock with your front bumper, but aren't going over a certain speed, I don't think it would set off the airbags. However, I'm no airbag expert, neither am I an engineer to that extent, I just did a bit of research to educate myself.
The airbag system is really complex in these new cars, so it calculates speed and impact and makes it's own decision whether the impact is enough to need airbag deployment. Replacing the crash bar with a bumper, removes that piece of foam, which in a sub-5mph impact, would absorb the impact forces and lessen the chance of an airbag deployment. But other than that, the system still works exactly as it would with a normal bumper.
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A nice honest discussion that would serve other manufacturers and vendors well.
I'm not the airbag engineer either, but I do know several and I understand that modern systems are far different from "activate above xx mph if the sensor is triggered. In short, the control unit makes literally millions of calculations to answer one question "If I deploy, will I reduce injuries?"
That's why many people say "I was in an accident and the airbag didn't deploy" and my question (which I learned from the airbag engineers) is "were there any injuries?" to which the answer has always been either "none" or "a bruise from a seatbelt".
With the first generation of airbags it was simple - you could swap bumpers to your heart's delight without issues, but today replacing the bumper cover (what we generally call the bumper) and the foam (whose main function is to comply with the mph bumper ratings) and the absorber. Impact angle and severity are some of the things that are taken into consideration and swapping that for a hunk of metal may well change the way the system works.
As an aside, DOT doesn't "approve" anything - it is a manufacturer's responsibility to certify that the replacement parts meet all of the regulations. In this case, the main regulations are
here and
here
