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-   -   Crush Cans...necessary? (http://www.wranglerforum.com/f274/crush-cans-necessary-127556.html)

NFRs2000NYC 12-14-2011 02:37 AM

Crush Cans...necessary?
 
I have been bumper shopping, and noticed some have crush cans, some don't. At first I thought they were just "crush boxes" that take a low speed hit, crumple, and save your bumper from real damage, but then I notice some bumpers have these crush cans welded on, so there goes that theory. What are they for? Is it ok to have a bumper without them? I am looking at the Rugged Ridge Modular bumper without a winch, and see it has no crush cans, so I just wanted to make sure....

daggo66 12-14-2011 06:31 AM

They are designed to absorb impact and are not necessary.

blackforestgreen 12-14-2011 06:36 AM

daggo, do they have anything to do with the airbags?

daggo66 12-14-2011 06:39 AM

Quote:

Originally Posted by blackforestgreen (Post 1827014)
daggo, do they have anything to do with the airbags?


They do not.

blackforestgreen 12-14-2011 06:53 AM

wow, they really aren't needed are they!

daggo66 12-14-2011 06:58 AM

Please refer to post number 2. :D

daggo66 12-14-2011 07:04 AM

Car Bumper Components | eHow.com

Hatt-Attack 12-14-2011 07:30 AM

If all you are going to do with your Jeep is run over stuff then I would agree they are probably not needed. However, I don't think they are put on just for looks as they are normally pretty ugly. From ehow link posted above “Their design allows them to crush or give upon impact, allowing the bumper frame to flex inward with minimal damage.” – that’s a plus. There are realities to life on the road, especially with a winch leading the way. Here's a for instance - If your wife, girlfriend, daughter drive your Jeep and have a tendency to play with their phones while at stop lights and accidently let off the brake and 'lightly' rear end the car in front of them, you will be glad the crush cans are there.

Matador 12-14-2011 07:53 AM

Where are the airbag sensors located on the Jeep? I thought they were in the bumper behind the "crush cans"

daggo66 12-14-2011 08:42 AM

They have absolutely nothing to do with the bumper and are not deployed directly on impact as popularly believed. It has to do with the force of the sudden deceleration which is a result of the impact.

What You Need to Know About Air Bags, DOT HS 809 575

Daniel_M 12-14-2011 08:50 AM

Quote:

Originally Posted by Hatt-Attack (Post 1827086)
If all you are going to do with your Jeep is run over stuff then I would agree they are probably not needed. However, I don't think they are put on just for looks as they are normally pretty ugly. From ehow link posted above “Their design allows them to crush or give upon impact, allowing the bumper frame to flex inward with minimal damage.” – that’s a plus. There are realities to life on the road, especially with a winch leading the way. Here's a for instance - If your wife, girlfriend, daughter drive your Jeep and have a tendency to play with their phones while at stop lights and accidently let off the brake and 'lightly' rear end the car in front of them, you will be glad the crush cans are there.

Daggo is right on here. They are there for absorbtion and nothing else, he did not say they are on there only for looks. They are a good component when rolling with stock plastic bumpers. However, when upgrading to an aftermarket steel bumper attached to the frame, the crush cans are not neccessary therefore cut off most times. An aftermarket steel bumper is not going to crush in on impact and absorb most of the impact. You may destroy the car in front of you but...The super expensive AEV and ARB bumpers that utilize the crush cans may not even truly utilize them upon an impact either, unless they are tin or paper thin, which i doubt they are.

-Dan

Comac90 12-14-2011 02:22 PM

I don't think you guys are correct based on nothing more than my conversation with AEV. According to Dave at AEV the crush cans DO play a function with the airbags in preventing the airbag from going off at too low a speed on a direct impact on the frame rail ... 6mph being the threshold. The crush cans are the reason the AEV bumper is the first factory winch bumper to ever be 'approved' on a production Jeep by Chrysler; again, according to AEV.

The explanation makes perfect sense to me. I had the same inquiry when I was deciding between their premium bumper and the Milspec.

IMHO, obviously from my own build, I don't think it's a big enough issue to warrant having a bumper with them, though.

T

Daniel_M 12-14-2011 03:25 PM

Agree to disagree I guess. I can't bring myself to spend the rediculous amount of money for their bumpers. I can say that there are no sensors in the cans or bumper area, so I don't know how they can affect the airbag deployment. I guess the concensus, even to the guys running AEV, the cans are not NEEDED but they like having them.:whistling:

-Dan

Nvrmor 12-14-2011 03:43 PM

Quote:

Originally Posted by Comac90 (Post 1827903)
I don't think you guys are correct based on nothing more than my conversation with AEV. According to Dave at AEV the crush cans DO play a function with the airbags in preventing the airbag from going off at too low a speed on a direct impact on the frame rail ... 6mph being the threshold. The crush cans are the reason the AEV bumper is the first factory winch bumper to ever be 'approved' on a production Jeep by Chrysler; again, according to AEV.

The explanation makes perfect sense to me. I had the same inquiry when I was deciding between their premium bumper and the Milspec.

IMHO, obviously from my own build, I don't think it's a big enough issue to warrant having a bumper with them, though.

T

Yup that was my understanding from dave as well. i'd rather have to replace a crush can than an airbag deploying, possibly causing injury, and then the replacement cost.

rics1997 12-14-2011 03:58 PM

The thing is Dave at AEV has a interest in saying that since their bumpers have crush cans. It's sort of like asking a republican if Obama is doing a good job. Not to say that Dave doesn't believe what his marketing team tells him either.

I bet if you call K&N they will give you a convincing reason to put K&N filters on your Jeep too.

Comac90 12-14-2011 04:00 PM

Quote:

Originally Posted by Daniel_M (Post 1828064)
Agree to disagree I guess. I can't bring myself to spend the rediculous amount of money for their bumpers. I can say that there are no sensors in the cans or bumper area, so I don't know how they can affect the airbag deployment. I guess the concensus, even to the guys running AEV, the cans are not NEEDED but they like having them.:whistling:

-Dan

No, they are needed if you want to help ensure no low speed airbag deployment. Despite lack of sensors 'in the bumper', my understanding is it has to do with the deceleration the sensor detects. The sensor doesn't have to be in the bumper to detect that.

... And, "rediculous" is relative. :D Try buying aftermarket parts for ANYTHING British. :ROFL:

T

Comac90 12-14-2011 04:16 PM

Quote:

Originally Posted by rics1997 (Post 1828154)
The thing is Dave at AEV has a interest in saying that since their bumpers have crush cans. It's sort of like asking a republican if Obama is doing a good job. Not to say that Dave doesn't believe what his marketing team tells him either.

I bet if you call K&N they will give you a convincing reason to put K&N filters on your Jeep too.

:rofl: I don't know that I'd go quite that far with your comparison. The only people who think Obama is doing a good job are those who believe that gov't is the answer to every question and personal liberty is an afterthought ... :whistling: ... and that includes a whole lot of people who are independents and libertarians. :D :rofl:

But, I digress ... remember up until a couple of months ago AEV sold both. Totally a guess, but I would imagine it's cheaper to make and more profitable to sell a stamped steel bumper without crush cans. And, it still remains that the hoop-less AEV bumper with crush cans is the first winch bumper ever to be approved by Chrysler to come from the factory on an airbag-equipped jeep.

Either way, I think we all can agree that there are plenty of great choices out there for those who don't want crush cans and/or don't want to pay AEV prices.

T

Hatt-Attack 12-14-2011 04:17 PM

Quote:

Originally Posted by Daniel_M (Post 1828064)
so I don't know how they can affect the airbag deployment.
-Dan


You run headfirst into a wall with a helmet - ouch. You run head first without a helmet – you’re a vegetable. The stock airbag sensors are set to release with certain amount of de-acceleration calibrated with stock bumpers as part of system. The airbag sensor doesn’t know you just replaced plastic bumper with a reinforced piece of steel that will simply transmit shock into frame it is rigidly attached to, which in turn airbag sensor is attached. So now the sensor trips at 2 mph collision instead of 6mph. In low speed collision, the extra money for the cans would easily pay for themselves versus replacing the deployed airbag(s). Fact that cans are absorbing (low level) of energy, may even save you a broken nose.

KarlG 12-14-2011 04:17 PM

Quote:

Originally Posted by Comac90 (Post 1827903)
I don't think you guys are correct based on nothing more than my conversation with AEV. According to Dave at AEV the crush cans DO play a function with the airbags in preventing the airbag from going off at too low a speed on a direct impact on the frame rail ... 6mph being the threshold. The crush cans are the reason the AEV bumper is the first factory winch bumper to ever be 'approved' on a production Jeep by Chrysler; again, according to AEV.

The explanation makes perfect sense to me. I had the same inquiry when I was deciding between their premium bumper and the Milspec.

IMHO, obviously from my own build, I don't think it's a big enough issue to warrant having a bumper with them, though.

T

What he said.

Yes, they have a purpose in preventing unwanted airbag deployment in low speed frontal collisions by mitigating deceleration forces. That is why they or similar design features are on OEM bumpers.

If you don't care and accept a low speed impact with a non crush can equipped bumper may result in an inadvertent deployment, that is fine.

"It's not important to me and I want a non crush can equipped brand x bumper on my Jeep instead" is totally valid, and more power to 'ya.

Statements regarding crush cans such as "They aren't needed", or "They are pointless or serve no purpose or aren't necessary" which pop up in some discussions just aren't true.

2012-Rubicon 12-14-2011 04:19 PM

Quote:

Originally Posted by rics1997
The thing is Dave at AEV has a interest in saying that since their bumpers have crush cans. It's sort of like asking a republican if Obama is doing a good job. Not to say that Dave doesn't believe what his marketing team tells him either.

I bet if you call K&N they will give you a convincing reason to put K&N filters on your Jeep too.

That's really not fair. The reality is its up to you in the end. The crush cans lower the impact forces registered by the accelerometers and therefore will reduce "low speed" air bag deployment, that's not makerting, that's physics.

rics1997 12-14-2011 04:26 PM

I can see the effects of a car and crush cans but not as much in a Jeep. Of course there is some effect but the solid steel frame is right near the crash point. There may be a 1 maybe 2 mph difference when the air bags may deploy because of crush cans but there is also a greater change at front bumper damage with crush cans. I know that before I changed bumpers, I gave some one a slight push on the trail from being a little stuck (Silverado). And it damaged my stock crush cans bad enough to notice. I think that the JK tank will do just fine in a crash with steel bumpers with no crush cans. Not sure the other side will do as fair though.

2012-Rubicon 12-14-2011 04:30 PM

Quote:

Originally Posted by rics1997
I can see the effects of a car and crush cans but not as much in a Jeep. The solid steel frame is right near the crash point. There may be a 1 maybe 2 mph difference when the air bags may deploy because of crush cans but there is also a greater change at front bumper damage with crush cans. I know that before I changed bumpers, I gave some one a slight push on the trail from being a little stuck (Silverado). And it damaged my stock crush cans bad enough to notice. I think that the JK tank will do just fine in a crash with steel bumpers with no crush cans. Not sure the other side will do as fair though.

Yes,your right the Jeep will be fine. The question is is the driver going to eat an airbag or not? Lol

rics1997 12-14-2011 04:37 PM

Well I was in a small accident a few weeks back, My Jeep and myself was perfectly fine. Not a scratch. Guarantee if I had stock bumper on the outcome would not have been the same at least for my Jeep. My solid steel bumpers save my Jeep from having to see a lot of body work. Hit a full size deer at 40mph. Not a solid object but would have cause severe damage stock. I will risk my airbag deploying at 5 mph instead of 6mph in a solid hit knowing I have that secure of a bumper.

2012-Rubicon 12-14-2011 04:50 PM

Quote:

Originally Posted by rics1997
Well I was in a small accident a few weeks back, My Jeep and myself was perfectly fine. Not a scratch. Guarantee if I had stock bumper on the outcome would not have been the same at least for my Jeep. My solid steel bumpers save my Jeep from having to see a lot of body work. Hit a full size deer at 40mph. Not a solid object but would have cause severe damage stock. I will risk my airbag deploying at 5 mph instead of 6mph in a solid hit knowing I have that secure of a bumper.

Right, no one was arguing that. In fact I concur. Honestly I don't even like airbags if I had my way I would have bought my Jeep without them. It's just that others have to make that descision as well.

ThePalmBeachYeti 12-14-2011 05:00 PM

Quote:

Originally Posted by daggo66 (Post 1827218)
They have absolutely nothing to do with the bumper and are not deployed directly on impact as popularly believed. It has to do with the force of the sudden deceleration which is a result of the impact.

What You Need to Know About Air Bags, DOT HS 809 575

Post Diamler Chrysler

but pre Diamler Chrysler, well the video explains it all

old lady hits car with her bag and air bag deploys - YouTube

OutlawJK 12-14-2011 05:31 PM

One way of looking at it is, anything that can absorb energy of an impact lessens the impact to the crash dummies(read YOU)

remember those 50's model cars built like tanks, when they encountered an impact the energy was transfered directly to the passengers,

as far as the bumper on a Jeep, I'm sure the crush cans are there for a reason

NFRs2000NYC 12-14-2011 06:41 PM

Technically speaking, everyone is correct. However, the crushcans are there to "crush" and save the car from sudden deceleration at low speeds...which is true. The big variable is, what you actually hit. If you hit a solid object (ie 100 year old oak) then ALL the forces are going to go through the frame if you have no crush cans, with a high probability of airbag deployment. However, if you hit a car, or a deer, they ARE the crush cans. Cars' sheetmetal or Rudolphs soft meat will absorb the energy, hence why people are fine with solid steel bumpers.

I do think they do have to deal with airbag deployments indirectly (they reduce the number of g's on a low speed impact) but unless you hit a solid object, they should not matter.

daggo66 12-14-2011 08:17 PM

Crush cans only help absorb impact if they are in the impact area. If you hit a pole in the middle of your bumper, or a tree or a rock, what good were they?

Yella 12-14-2011 08:30 PM

Quote:

Originally Posted by rics1997 (Post 1828154)

It's sort of like asking a republican if Obama is doing a good job.

No he's not.

NFRs2000NYC 12-14-2011 08:41 PM

Quote:

Originally Posted by daggo66 (Post 1828779)
Crush cans only help absorb impact if they are in the impact area. If you hit a pole in the middle of your bumper, or a tree or a rock, what good were they?

True. Crush cans are literally for the situation like the video above with the old lady...so that a slight parking bumper doesn't set off the airbags. However, it seems the Jeep doesn't have that problem. I am sure a number of members here have a solid bumper, and have knocked it while wheeling, and did not deploy their airbags. Surely jeep engineered the sensors to withstand slight offroad bumps.

P.S. To the AEV crush can comment....it seems like BS to me. If they are welded on, then how are they "crush" cans? Since they are now part of the bumper, the energy gets transferred right through the welds and into the frame....seems like snakeoil to me.


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