Safety of steel bumpers

[PSUTE]

The only thing I've hit in years are 3 deer. Cracked plastic behind the bumper of my Sierra, second one a dent in the metal of the same Sierra (75 mph) Third one $8000 + damage to Chevy Trax, was able to limp home with it after tying the plastic up off the tire with the headlight wiring harness. Yeah, going with the steel bumper. Don't want there to be any question about the next time...

Sponsored

 

[mneblett]

The bumper doesn't really have anything to do with how crashworthy the vehicle is. Steel or plastic, the way the energy is transferred is built into the vehicle throughout. The entire vehicle is engineered to both absorb, and displace, energy away from the occupants.

A plastic bumper is just a sheet of plastic shaped to be aesthetically pleasing. There is a piece of Styrofoam under it that is built to withstand a 2 mph - 5 mph impact. It is broken in the most insignificant of impacts and is often broken without you knowing it. The energy it displaces is minimal. It is attached to a steel crossbeam which is mounted to crumple zones.

A steel bumper is only a piece of steel that has been formed to be aesthetically pleasing. Instead of Styrofoam, it is mounted to "rails" and a crossbeam that have crumple zones (same as the plastic bumper). Those crumple zones are designed to "absorb" the energy.

The design of the frame/unibody moves or transfers and displaces the energy. The curves you see in a body on frame are designed to bend at different rates. You have crumple zones where the bumpers mount, at the ends. You then have strategically designed and places/zones meant to bend. If you're interested, you can look, follow, from the end of the vehicle to the passenger compartment and see bends, holes, and dimples in the frame or unibody. These are all designed as separate points in the overall structure that are going to absorb or displace the energy of an impact.

If you spend some time looking at a vehicle that has been in an accident, you can literally "follow" the damage from impact to where it has been displaced/absorbed enough that it stops travelling through the vehicle. In minor impacts you'll see the damage at the impact site and one or two "dimpled" areas back. In more severe accidents you'll follow it to the firewall or if it is bad enough, into the passenger compartments. Even your windshield is designed as a structural component of the vehicle.

All of this is designed to protect the passengers and minimize the transfer of energy to the occupants. In addition, active safety measures are also in place, namely airbags. They will deploy even when the transfer of energy is minimal to the occupant, even when the "crumple zones" don't reach the passenger compartment.

No joke, if you have a chance to go to a wrecking yard and have someone point out the damage it'll be eye opening. Someone trained in damage analysis (ASE Certificate B6) can, as I said above, literally follow the transfer of energy from the damage and impact and show you the energy transfer throughout the vehicle. It's kind of cool in a geeky sort of way.

As to your concern, plastic or steel, the bumper isn't going to make a difference on the felt energy/impact in the passenger compartment.

Excellent summary. The only thing I'll add is this is absolutely correct for stock bumpers. Many folks install big honkin' battleship armor plate bumpers. These can be quite rigid, but the above answer is still correct: the multiple layers of crush between the bumper and the passenger compartment will handle the majority of the protection (features such as frame rail crumple zones, engineered break-away suspension and engine/transmission mounts (like the bars that help steer the wheel away from the driver's feet, the engine/transmission on longitudinal drivetrains are directed downward under the passenger compartment to minimize power train intrusion -- which of course also absorbs crash energy).

Something else to keep in mind is that the principal purpose of all these crush features is to increase the duration of the collision. The shorter the collision, the higher the deceleration force on the driver. High deceleration=high injury-causing force. Make the collision last a few tens or even hundreds of milliseconds longer, and the driver deceleration is significantly lower.

Some people complain that cars fold up too easily these days, resulting in more total losses. Yet all that crushing likely spared (or will spare) them more serious injury.

 

[Jr87mustang]

Bronco crash bars.

Pretty sure you circled air on the back side of the Badlands, we were told they only have a front crash bar. Sasquatch doesn't have any. OBX and below have two.

 

[BroncoKong Jr.]

Pretty sure you circled air on the back side of the Badlands, we were told they only have a front crash bar. Sasquatch doesn't have any. OBX and below have two.

It's visible in that picture...

 

[Used2jeep]

I currently drive a JKU with steel bumpers (AEV as part of the Backcountry Package) and wonder about the degree to which the lack of a crumpling bumper makes the Jeep even less safe (current safety rating, I think, is just 1 star). I suppose with a steel bumper any impact will transfer all kinetic energy right to the driver. Anyone know about the safety differences between the two in a high-speed impact.

Low impact seems ideal for steel bumpers, but I worry more about the hazardous impacts.

I am under the impression that it is the area that the bumper attaches TO, the frame rail, that absorbs the most energy.

 

[Used2jeep]

Pretty sure you circled air on the back side of the Badlands, we were told they only have a front crash bar. Sasquatch doesn't have any. OBX and below have two.

It's"structural" air.

 

[Jr87mustang]

It's visible in that picture...

You do kinda see something back there, can't tell. That would be great if it is because that would mean for sure you can add 285/70x17 tires to OBX and below for sure. LEGEND said the Badlands only had one crash bar and the Sas didn't have any on the ones he looked at. Wish we had a better picture.

 

[Jr87mustang]

It's"structural" air.

It does kinda look like there is something there in that pic.

 

[AzScorpion]

Pretty sure you circled air on the back side of the Badlands, we were told they only have a front crash bar. Sasquatch doesn't have any. OBX and below have two.

These are from another thread here. There are a few more pictures on there too. I think you're right about SAS not having any crash bars.

 

[BroncoKong Jr.]

You do kinda see something back there, can't tell. That would be great if it is because that would mean for sure you can add 285/70x17 tires to OBX and below for sure. LEGEND said the Badlands only had one crash bar and the Sas didn't have any on the ones he looked at. Wish we had a better picture.

I thought they were on all trims, but of different lengths depending on tire size. I could've sworn we've seen them on Broncos with Sasquatch, but I could be wrong. In any case, they are simply bolt-on, so not hard to swap out or remove.

 

[AzScorpion]

I thought they were on all trims, but of different lengths depending on tire size. I could've sworn we've seen them on Broncos with Sasquatch, but I could be wrong. In any case, they are simply bolt-on, so not hard to swap our or remove.

They have smaller aftermarket ones ones for the Ranger so you can run 33's with. I'm sure there will also be some for the Bronco.

 

[Jr87mustang]

I thought they were on all trims, but of different lengths depending on tire size. I could've sworn we've seen them on Broncos with Sasquatch, but I could be wrong. In any case, they are simply bolt-on, so not hard to swap our or remove.

Well there is some debate on other forums about people that have had insurance problems after a wreck with crash bars removed or hacked off. If 33's fit a BD for sure I am skipping Squatch.

 

[HoosierDaddy]

"hard" solid steel cars were only dangerous in the 50s when all the other cars on the road were build like tanks

so unless you plan into crashing into a tree or wall , the more stiff your car is the safer it is running into soft cars

just not so good for the occupant of the other vehicle

Head, neck, chest and both leg injuries vs a possible foot injury.

 

[Mattwings]

I was a claims adjuster for several years. It was making to see the crumple zones in action. Some cars would look practically untouched from the outside, but the frank and floor would be crumpled a foot or more. Definitely has little to do with the bumpers! Lots of good details from the other posters. The technology keeps getting better and cars get safer all the time!

Sponsored