cons of front bumper replacement

[drno]

i can get a great deal on a lone star bumper/ grill guard. its a given that that i like the looks and know that if i hit something they lose. however, i am concerned that when you hang 250 lbs of steel that has the aerodynamics of a refrig on the front of your truck something has to suffer. any input on front end parts longevity, handling , milage ,etc will be welcome. i am not looking to do more harm than good for the sake of looks

 

[Jengle]

Before I mounted this one on my 3500, I could put my 200lbs on the front bumper and it wouldn't give. After the bumper change, I get on the bumper and it might drop 1/4-1/2 inch. Couldn't tell much, if any difference in ride, and not even a tenth of a drop in mpg. I do know I don't have to worry about smacking a deer in this area, though. One gets hit almost 3 per day, within 5 miles of the house. Neighbor whacked one in a car, about 1/2 mile from me.

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[RustyJC]

Although front bumper replacement can have a number of advantages, some of the "brute force" replacements may offer one or more of the following disadvantages:



1. Air bag functionality - the crush zone system and inertial impact sensors are calibrated to ensure that the air bags work when they should and don't go off when they shouldn't. As more impact will be transmitted to the frame instead of absorbed within the crush zone, there's a chance that the airbags could trigger in a minor "bump"-type parking lot impact.



2. Frame damage - if the bumper is built so stout that it doesn't give, what will? Quite possibly, the front frame rails.



Just a couple of things to consider.....



Rusty

 

[TBrennan]

I seriously doubt the 5 mph rated (actually I think for trucks there is no requirement) bumpers that come on modern trucks are even factored in or considered part of any crumple zone. They are just way too light to have any significant consequence at all. As such they are not relevant to air bag deployment which are inertia based sensors located inside the cab.



The frame has detents to allow it to crumple in zones and absorb impact. With a HD front replacement bumper you essentially are extending the frame forward so any large impact will start sooner, but shouldn't effect overall effectiveness of the system.



In any collision not hard enough to bend the frame the HD front bumper should offer considerable more protection to the truck's front end.

 

[Jetson]

There is no factory bumper.

30 lbs. of sheet metal is not a bumper.

 

[RustyJC]

I seriously doubt the 5 mph rated (actually I think for trucks there is no requirement) bumpers that come on modern trucks are even factored in or considered part of any crumple zone. They are just way too light to have any significant consequence at all. As such they are not relevant to air bag deployment which are inertia based sensors located inside the cab.

The front bumper, its supports, the radiator support, inner and outer fender panels, etc. are the crumple zone. When a "heck for stout" aftermarket bumper is bolted directly to the frame, this crumple zone is effectively eliminated and can no longer dissipate the collision forces, thereby attenuating the peak G loads transmitted to the passenger compartment. Instead, the unattenuated forces are transmitted directly into the frame where the higher peak G loading can trip the airbags' inertial sensors.



It's each individual's money and each individual's choice. The original poster asked if there were any potential downsides to the use of an aftermarket bumper. Elimination of the crumple zone function provided by the front sheetmetal is one such consideration.



Rusty

 

[Boondocker]

weight

Sheer weight as it pertains to GVW.



While one poster commented that the perceptable effect on handling & MPG was insignificant, you may still have a gross weight issue if your condition is border-line. Even though I love the looks of the Buckstop bumpers, I can't justify one based on the number of deer in Las Vegas. Add to that, my conscience can barely stand the sin of being over GVRW when the 5th-wheel trailer is pinned to my heavy Pullright slider hitch.



May name is Neil and I'm 400 lbs. over GVRW. Even though I'm 3000 lbs under GCWR, that doesn't make up for the over-GCVW problem and adding 200 lbs of bumper would just make it worse.

 

[thejeepdude]

Regarding stout bumpers setting off air bags in otherwise "small" collisions, I don't buy it. I understand the theory you're trying to prove, and I heard the same things from people when they first put the bags in Jeeps. However, in addition to the g-force sensors, they're tied into the speed sensor as well. If you're not going over the threshold speed (not sure what it is on a Ram), it won't go off no matter how suddenly you stop. I know for a fact this is true with my '98 Jeep with dual airbags, because I've crashed, smashed, and beat the crap out of it on many rocks, even ran into a solid wall of ice at about 10mph, and the bags never went off. And let me tell you that was some jolt!!



I'll take the extra assurance the beefy bumper gives me regardless of any miniscule amount of risk that is added in only a small set of non-ideal circumstances. The only one that should be worried about my beefy bumper is whoever made the mistake of cutting me off... "wow that kia has quite a cumple zone and my bumper not a scratch" :-laf

 

[TBrennan]

The front bumper, its supports, the radiator support, inner and outer fender panels, etc. are the crumple zone.

Rusty

I don't recall removing the radiator supports for my Busktop install. I still contend that the oem front bumper and supports are worth almost ZERO as a crumple zone.



I would need some test data showing a collision with the front bumper and without at a significant speed to make me believe any different. I think at 10 mph the front bumper is history. At 30 mph I think you would not know the difference if it was there or not.



Besides, with my Buckstop bumper, the idiot who just cut me off is my crumple zone. :-laf

 

[fkovalski]

i am concerned that when you hang 250 lbs... on the front of your truck...

Having heavier duty springs with the snow plow prep group is a nice option for this reason.

 

[tbrudder]

Regarding stout bumpers setting off air bags in otherwise "small" collisions, I don't buy it. I understand the theory you're trying to prove, and I heard the same things from people when they first put the bags in Jeeps.

I'd tend to agree.



My understanding is the only thing that will actuate the airbags is an acceleration greater than the threshold programmed into the airbag computer. In other words, when you're slowing down, if you slow down faster than what Dodge's engineers (or maybe the NHTSA/IIHS/DOT) decided was safe (i. e. , you just ran into something hard), the airbags pop, with the possibility of a lockout below a certain speed (I'm not really sure of that, but it's certainly plausible).



There are no sensors that detect the front of the vehicle crumpling and set off the SRS. But as Rusty said, by having a stout bumper connected to the frame, your initial deceleration in a frontal crash will be higher. How much higher depends on how the frame was put together, how fast you're going, and what you've just run into. None of this, however, will affect how the airbag deploys. Once you hit the threshold, out they come--you might manage to deploy them a few MPH lower if you hit something solid, but it's not going to keep them from going off in a collision where they're needed.



--Ty

 

[Ol'TrailDog]

The 250 additional pounds hanging on the front end of an already hefty Cummins was why I chose a 125 lbs aluminum bumper and grill guard. There are several options out there including Herd (www.herdusa.com), Aliarc, UTE, and Denver Off-Road.



Plus, rumor has it the aluminum is suppose to have better impact characteristics than steel - but then I'm just a sucker for a good line and not a physicist.



I just couldn't handle the risk of pounding an unnimble or maladroit ungulate in this neck o' da woods with the stock tinfoil and plastic imitation bumper. Too many close calls and a couple that would have been nice if they would have been close calls. :{

 

[Deezul1]

I had a Bozo back into the front of my truck in a parking lot (other Dodge, stock bumper) when I wasnt there and thankfully he was an honest person and left his ph# as there was $1800 worth of damage and you couldnt even see it unless you looked close. I like the solid bumper I have now if for no other reason than that.

 

[EBottema]

Guys, don't worry about the crumple zone.



The bumper is tieing the frame together and acts like having a huge front frame brace. It makes the truck stronger as a whole. However, if you get into a major accident, the force might not be distributed as evenly as the truck was designed to from the factory. However, the stock bumper makes the front end week, not a good cross support!

 

[RustyJC]

Guys, don't worry about the crumple zone.

You might want to plug some numbers into the following equation:



a = (Vf^2 - Vo^2) / 2s



where



a = average deceleration [negative acceleration] (in feet per second squared)



Vf = final velocity (in feet per second)



Vo = original velocity (in feet per second)



s = distance traveled during deceleration (in feet)



Peak acceleration values will be greater than the average acceleration value that comes out of this formula.



Try assuming that you hit a brick wall at 30 MPH (Vo = 44 feet per second) that brings you to a stop (Vf = 0 feet per second). Make your own assumptions regarding the distance traveled (crumple zone) with and without the aftermarket bumper during this deceleration - I'd use maybe 2 feet stock versus 0. 5 foot with the aftermarket bumper. See what the numbers say. If you want to convert the acceleration into g's, divide the acceleration you get above by 32 feet per second squared.



Rusty

 

[thejeepdude]

You equation is trying to demonstrate the "small set of non-ideal circumstances" that I mentioned earlier. However, I think it fails. You don't take into consideration the mass of the wall vs. the mass of the truck, and the decellerating forces of our dense heavy truck smashing the wall. Most brick walls are only 1-2 layers of brick, sometimes reinforced with rebar, but not always. I understand your point, but I think you'd have to use a brick retaining wall, or a deep solid ditch, or a giant sequoia tree in your example to make the point. At any rate, the increased chance of whiplash when running into a large, fixed, unmovable object is worth it compared to the more likely incident of running into a smaller, lighter, movable object on the road. Especially since the first scenario is more likely to kill you whether you have a crumple zone or not. That's my 2¢ anyways.

 

[RustyJC]

Do whatever you want. The laws of physics and mechanics still stand. The original poster asked if there were any "cons" - why not be objective about the subject and admit that there are. Then, in this individual objective analysis, if the pros (saving the sheet metal) outweigh the cons (higher accelerative forces in the event of an accident), make a subjective decision and buy the aftermarket bumper. Ignoring the cons doesn't serve anyone's purposes (other than the bumper vendors).



As reference, one might want to consider what NASCAR has learned about building "stiff" stock cars and the importance of crumple zones to manage forces in a crash situation such as those involving Adam Petty, Dale Earnhardt, etc.



Rusty

 

[TBrennan]

Make your own assumptions regarding the distance traveled (crumple zone) with and without the aftermarket bumper during this deceleration - I'd use maybe 2 feet stock versus 0. 5 foot with the aftermarket bumper. See what the numbers say. If you want to convert the acceleration into g's, divide the acceleration you get above by 32 feet per second squared.

Rusty

This is where I disagree with you. Your assertions and assumptions are all based on their being a single crumple zone, all in front of the frame rails and that the frame rails are completely unyielding, even in the event of hitting an immovable object. Modern vehicles are designed with mutliple crush zones that include the frame in our case. Somehow you assume on a stock truck, you have 2 feet from the front of the bumper to the frame rails which don't bend. Hitting an immovable wall at 30 mph will bend the frame rails which I think are detented just for this purpose, and even if they didn't I bet the energy absorption dissipated by the oem bumper "crumple zone" is not significant.

 

[RustyJC]

Hitting an immovable wall at 30 mph will bend the frame rails which I think are detented just for this purpose, and even if they didn't I bet the energy absorption dissipated by the oem bumper "crumple zone" is not significant.

That's why I said assume 6" crumple in the case of the aftermarket bumper - the frame (a much stiffer member than the body panels) is taking all of the forces and will crumple. The design of most vehicles, though, is that the front sheetmetal takes the initial forces (the other 18" in my example) and is sacrificed before the frame starts giving way. If you think they'll crush the same distance with or without the aftermarket bumper, I'll be glad to show you a Ram 2500 that was involved in an accident with a "heck for stout" (not sure of the brand) aftermarket bumper. The front sheet metal and bumper look great (relatively speaking), but the frame is bent. The fact remains - all else being equal, if you halve the crush distance, you double the accelerative forces transmitted to the truck and its occupants. If (as in my example) you cut the crush distance to 1/4 of stock, the accelerative forces are four times as high. Simple physics.



I believe at least one of the aftermarket bumper manufacturers (is it Buckstop, the Aussie one, or ???) understands this and has engineered his bumper to provide controlled crush to keep the airbag system working as designed. At least, that's what their ad copy said.



Rusty

 

[duaneparks]

As the owner of a "heck for stout" front end replacement bumper, I'll relate my experiences. One of the main drawbacks that I've encountered is that sheetmetal bends and deforms MUCH quicker than the bumper. As a lady pulled into my lane from a stopped line of traffic, I put my front bumper 5" into her BMW. The impact was at about 10 mph and since I stopped before she did, her car received damage in the passenger side front and rear doors (and interior panels), and right rear quarter. When all the dust settled, her insurance ponied up over $5K to fix her car, and the only noticeable damage I had was a scratch on my front bumper.



Had there been a passenger in that car, or had the speed differential been greater, that could have been a serious accident. I remind myself of this EVERY time I start my truck, and I do tend to watch out for those who do not or will not watch out for themselves around me.



Also, in tight parking lots extreme care has to be taken to keep from damaging other vehicles. The saying "Bull in a china shop" comes to mind.

Duane