Bumper Pulled Off Bronco

[monsterfd]

By comparison, the stock bumper has the recovery points directly attached to the frame horns, so they will withstand higher loads (even without reinforcement).

Factory also has a backing plate behind the horn. I’m sure this acts as a truss to some degree

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[geargeek]

BTW disclaimer regarding tradeoffs/risks of adding frame horn reinforcement, @zuke put it best:

A quick disclaimer here also;

/Disclaimer

While I've talked about the frame horn reinforcement as an important thing to do for all cases of extra stress on the frame horns, I think it's important to note a couple things;

My reasoning is that's it's most important for a flat tow setup more because of the stakes involved, and the criticality of a safe tow setup. Flat towing with an RV puts many people at risk, and a failure in this situation is most likely to occur on a highway at speed with traffic around. There are many innocent folk's lives at risk that aren't aware of the possible dangers.

In the other cases, (recovery and winching) The chances of an outright failure are much lower, all the folks around are aware of the risks they are taking already, and the possible number of folks affected should be much lower. Also, anyone who does recovery, via winch or kinetic rope, should be inspecting their equipment after any trip where they perform recoveries, so should see signs of problems and take corrective actions before reaching the point of failure.

In all cases, be aware that the frame horn area we are talking about includes part of the Crash Crumple Zone designed into the Bronco, so taking steps to reinforce the area also changes the crash dynamics (And likely Air Bag deployment parameters) of the vehicle, so that is a risk we take when we do any modifications to that area of the Bronco.

/End_Disclaimer

Carry on all!

 

[swamp2]

BTW disclaimer regarding tradeoffs/risks of adding frame horn reinforcement, @zuke put it best:

Can't quite quote @zuke here, but....

Totally disagree with the risk to airbag deployment. Changing the crumple zone and crash dynamics slightly won't affect airbag deployment. If anything, making the chassis stiffer would cause airbag deployment earlier and more easily. Airbags are simply connected to an accelerometer(s) and once a threshold is exceeded they trigger. Frame horn reinforcement will not in any significant way alter the rapid deceleration in any collision with a stationary or moving object at any reasonably high speed.

 

[geargeek]

Can't quite quote @zuke here, but....

Totally disagree with the risk to airbag deployment. Changing the crumple zone and crash dynamics slightly won't affect airbag deployment. If anything, making the chassis stiffer would cause airbag deployment earlier and more easily. Airbags are simply connected to an accelerometer(s) and once a threshold is exceeded they trigger. Frame horn reinforcement will not in any significant way alter the rapid deceleration in any collision with a stationary or moving object at any reasonably high speed.

It seems Ford thinks it’s an issue: the Ford Performance winch kit includes frame horn reinforcements, and it requires an airbag software update after installation.

Changing crash dynamics is kind of by definition changing acceleration rates of the different parts involved, so, I think accelerometer readings would be different.

edit: BTW airbag timing is critical - too early can be as bad as too late.

Those frame horns are designed to crumple, so reinforcements could affect the crash dynamics - not just airbags. Unless it’s tested or at least modeled, it’s hard to say what the impact would be.

I’m not saying don’t do it, just making the potential risks visible.

edit: and if I had a winch on my bumper, I would definitely add frame reinforcements, and probably the airbag update.

 

[SierraBronco]

Alrighty. I know the owner. In fact I invited him to run that trail. That day I also disconnected his driveline after the D60 had issues, and reset his computer to give him front wheel drive for as long as possible to get him to the sand that day. Here’s what happened: A flat strap was hooked up to both recovery points on the bumper. A flat strap was decided on as there were still many climbs on the rocks to get out, and a potential energy rope can sometimes cause issues pulling the tow vehicle back in steep rock crawling situations. They successfully pulled him all the way out of the rocky bits without issue to the dunes, and by then the tow vehicle became hot and needed a break. At this point random raptor dude that noone knew offered to help. They were going to swap to the potential energy rope for the sand but for whatever reason decided to just run how they had it. Raptor bro slowed down before starting the climb, putting slack in the strap, then gunned it for momentum, pulling the bumper cleanly off the non-braced OEM mounts and damaging one side of the bumper with the way the mounts broke off.

I make fun of @dv8 a lot for their preposterous branding choices, but they were actually pretty badass and are sending the owner a replacement bumper for free.

 

[geargeek]

Alrighty. I know the owner. In fact I invited him to run that trail. That day I also disconnected his driveline after the D60 had issues, and reset his computer to give him front wheel drive for as long as possible to get him to the sand that day. Here’s what happened: A flat strap was hooked up to both recovery points on the bumper. A flat strap was decided on as there were still many climbs on the rocks to get out, and a potential energy rope can sometimes cause issues pulling the tow vehicle back in steep rock crawling situations. They successfully pulled him all the way out of the rocky bits without issue to the dunes, and by then the tow vehicle became hot and needed a break. At this point random raptor dude that noone knew offered to help. They were going to swap to the potential energy rope for the sand but for whatever reason decided to just run how they had it. Raptor bro slowed down before starting the climb, putting slack in the strap, then gunned it for momentum, pulling the bumper cleanly off the non-braced OEM mounts and damaging one side of the bumper with the way the mounts broke off.

I make fun of @dv8 a lot for their preposterous branding choices, but they were actually pretty badass and are sending the owner a replacement bumper for free.

Thanks for the info! I was hoping someone was in the know. Glad he gets a free replacement. Sounds like it was a very hard hit.

You said a flat strap was hooked to both recovery points, how long was the strap?

 

[swamp2]

It seems Ford thinks it’s an issue: the Ford Performance winch kit includes frame horn reinforcements, and it requires an airbag software update after installation.

Changing crash dynamics is kind of by definition changing acceleration rates of the different parts involved, so, I think accelerometer readings would be different.

edit: BTW airbag timing is critical - too early can be as bad as too late.

Those frame horns are designed to crumple, so reinforcements could affect the crash dynamics - not just airbags. Unless it’s tested or at least modeled, it’s hard to say what the impact would be.

I’m not saying don’t do it, just making the potential risks visible.

edit: and if I had a winch on my bumper, I would definitely add frame reinforcements, and probably the airbag update.

Although I largely agree with some of what you've said here above, it is still losing sight of the forest for the trees. Also, you seem to not acknowledge that the size of an effect must be related to the size of the cause.

It sounds to me like Ford is being extremely conservative here with such a software update. It could even be a legal requirement, FMVSS/NHSTA/DOT requirement or also a simple CYA (Ford Performance covering their ass) as opposed to being a true technical requirement. That said, a winch, different front bumper and frame horn reinforcement is a much more significant change than just a horn reinforcement, which was the basis for which I replied.

I'd still place a very large wager on one not being able to discern the presence or absence of just a horn reinforcement from any crash accelerometer data from a vehicle. It's just too small of a change compared to the total momentum/energy of a fast moving vehicle and the entire rest of the vehicle structure.

Absolutely agree that airbag timing, both ignition, reactions and venting are critical, but again, see just above. The signal in acceleration vs. time from any crash large enough to deploy an airbag is pretty well a tall/narrow triangular(ish) or perhaps Gaussian(ish) pulse. This overall shape is determined primarily by the vehicles and impactor speed and mass. Stiffness and overall length of the crumple zones are second order contributors. Horn reinforcement is like a fourth order effect. It's almost like saying an auxiliary battery or a larger turbo will interfere in the overall safe operation of an airbag system. I'm exagerating here a bit, but it is not entirely dissimilar. Once a certain slope and magnitude are obtained in the acceleration, boom, airbag time. Sure the devil is in the details and there are actually a slew of redundant, discriminatory and elimination of false positive senor data needed, but the essense is absolutely and simply, just a big hit.

Lastly, there are infinitely more and more serious things to worry about when thinking or worrying about vehicle safety (and mods) than horn reinforcements or even the entire system of changes mentioned above. A few very obvious ones are - drive a heavy vehicle, buckle up, don't drink/phone while driving and of large relevance here - practice conservative recoveries.

 

[Sloth]

Not to knock DV8…
Any thoughts on the location of the recovery points on that bumper? I suspect they’d create additional leverage being located ahead of the winch and that much further away from the frame horns.

 

[SierraBronco]

Thanks for the info! I was hoping someone was in the know. Glad he gets a free replacement. Sounds like it was a very hard hit.

You said a flat strap was hooked to both recovery points, how long was the strap?

I didn’t look at the specs myself but based on how far it was from the tow vehicle I’d venture a guess at 30’

 

[geargeek]

Although I largely agree with some of what you've said here above, it is still losing sight of the forest for the trees. Also, you seem to not acknowledge that the size of an effect must be related to the size of the cause.

@swamp2 I agree with most of what you said. However, I don't have any hard data to quantify the risk, and I doubt you do either. Saying it is a fourth order effect is speculation. The risk is not zero, so I thought it was worth sharing.

That said, if I owned that bumper, I would add the reinforcement.

 

[geargeek]

Not to knock DV8…
Any thoughts on the location of the recovery points on that bumper? I suspect they’d create additional leverage being located ahead of the winch and that much further away from the frame horns.

Yes - I mentioned this in an earlier post in this thread:
From the video evidence, the flat nuts definitely pulled out of the bumper on the passenger side - this could have started due to bending of the frame horns before they failed, or it could have just been very high twisting forces on the bumper. With that bumper, the recovery points are offset and in front of the frame horn connection, so any recovery force is going to create a twisting force on the bumper and frame horns. By comparison, the stock bumper has the recovery points directly attached to the frame horns, so they will withstand higher loads (even without reinforcement).

 

[Tonka Bronka]

It seems Ford thinks it’s an issue: the Ford Performance winch kit includes frame horn reinforcements, and it requires an airbag software update after installation.

Changing crash dynamics is kind of by definition changing acceleration rates of the different parts involved, so, I think accelerometer readings would be different.

edit: BTW airbag timing is critical - too early can be as bad as too late.

Those frame horns are designed to crumple, so reinforcements could affect the crash dynamics - not just airbags. Unless it’s tested or at least modeled, it’s hard to say what the impact would be.

I’m not saying don’t do it, just making the potential risks visible.

edit: and if I had a winch on my bumper, I would definitely add frame reinforcements, and probably the airbag update.

My personal experience, after installing the FP/Warn kit, I took the Bronco in to my local dealer for something else at the time and asked them to update the airbag for the winch install. I was told nah, that doesn't need done.

 

[geargeek]

My personal experience, after installing the FP/Warn kit, I took the Bronco in to my local dealer for something else at the time and asked them to update the airbag for the winch install. I was told nah, that doesn't need done.

Interesting. If it was me, I'd insist they do it - for the personal liability protection. The dealership really has no skin in the game.

 

[HotdogThud]

Starting in the video below at 15:50, apparently a broken Bronco was being towed in by a Raptor, and at some point the Raptor gave it a hard yank,

Edit: A witness said they used a flat strap to connect to both recovery points, so I was wrong about that part.

^^^
The real heroes of the story here.

tow strap + hard yank = broken parts, and a high chance that someone dies.

Need to use a bridle to tow straight? sure, makes sense, get a damn kinetic rope that's 15' long then

 

[indio22]

It seems Ford thinks it’s an issue: the Ford Performance winch kit includes frame horn reinforcements, and it requires an airbag software update after installation.

Changing crash dynamics is kind of by definition changing acceleration rates of the different parts involved, so, I think accelerometer readings would be different.

edit: BTW airbag timing is critical - too early can be as bad as too late.

Those frame horns are designed to crumple, so reinforcements could affect the crash dynamics - not just airbags. Unless it’s tested or at least modeled, it’s hard to say what the impact would be.

I’m not saying don’t do it, just making the potential risks visible.

edit: and if I had a winch on my bumper, I would definitely add frame reinforcements, and probably the airbag update.

On the subject of crash dynamics, I'll give props to the lowly ugly plastic rear bumper. My Bronco got rear-ended recently, and I think the plastic bumper having a certain amount of give/cushion, might have helped reduce severity of impact. With the metal bumpers the full impact is transferred to the frame.

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