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HD bumpers on airbag equipped cars?


Jon White
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As it says really? What are the options?

I'm aware that there are some HD bumpers specifically designed for air bag cars, that have the crumple zones built into them. However these seem few and far between, and I've not yet come accross anyone that lists one for a classic rangie with aribags. However has anyone just bolted a standard HD bumper on?

On the same vain anyone who has done that then later crashed it?

Another school of thought simply says remove the fuses to the air bag system - on the philosophy thats its now over 10 years old, so probably doesnt work properly anyway!

Any thoughts?

Thanks

Jon

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When 5th gear tested old airbags by crashing things (just for a change) they found they all still worked, and that was in 10+ year old cars IIRC.

Personally though I'd take the fuse out and maybe sell the airbag on eBay as sometimes they go for silly money.

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well, can't speak for other makes but LR's use accelerometers and and SRS ecu to control airbags. The norm is to locate two at front, usually behind bumper and one in centre of car. Two at front measure front to back acceleration, centre is side to side. Some like the RR's have a tilt sensor too. ECU monitors acceleration/deceleration of all sensors and certain thresholds trigger airbags.

They are designed to work with a car's crumple zones and to inflate the cars airbags at an optimum time. Without altering ECU there is no way an HD bumper manufacture could mimic the characteristics of the standard bumper. However, some maintain OEM crash cans on front of chassis to try and go some way towards this, however, I see this as pointless as you've now introduced a weak point to a front 'HD' bumper.

So if you remove crash cans and fit an HD bumper what's going to happen in a frontal impact? Less force is going to be absorbed and the deceleration will be higher. This will mean that an airbag would trigger sooner, but as your head is heading towards the wheel at a faster rate it's probably not a bad thing! ;) ;) Not exactly scientific but that's what happens.

Fitted P38 with HD winch bumper, (custom made thanks to RogueVogue :) ) and numerous banks and a few trees hit fairly hard with no problems. Unfortunately, my bigger incident with a tree whilst sliding down a steep hill in Devon was with the standard bumper on, so no proof there, other than airbag threshold seems high ;)

Here's a pic..

RRtyres033.jpg

Cheers

Steve

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Thanks - thats useful to know!

i was concerned that otherwise the first rock i hit would set the airbags off!

System on mine is exactly as you descibe - a sensor on each chassis rail behind the bumper. The crush cans are part of the standard fit front bumper, but the problem i have is that i am missing the plastic covers that cover the crush cans, and apparently the part number has gone end of life! Therefore I thought just stick an HD bumper onto it......

Cheers

Jon

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Thanks - thats useful to know!

i was concerned that otherwise the first rock i hit would set the airbags off!

System on mine is exactly as you descibe - a sensor on each chassis rail behind the bumper. The crush cans are part of the standard fit front bumper, but the problem i have is that i am missing the plastic covers that cover the crush cans, and apparently the part number has gone end of life! Therefore I thought just stick an HD bumper onto it......

Cheers

Jon

When I first got my Camel Freelander I asked that question to LR SV dept and Safety Devises as to weather the both the Airbags worked still and although their murcury switch controled it should not affect it so no matter how much armoure is on the front of the car they will still work.

Ali did most of the digging on this subject and know more than I do on this subject.

In theory anyway

I don't know what the RRC system is....

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I can testify that the threshold is reasonably high for the airbags if the car is wearing standard bumpers - they didn't deploy on this ten-year old Discovery.

P1010022s.jpg

I have seen a freelander that hit a tree but the airbag didn't deploy but like the disco in the photo it didn't hit its target square.

but I though the air bags only deploy in the event of a major crash and not a shunt so if you don't hit something square the car will bouce off meaning the majority of the force and energy is lost.

if that makes any sence

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The system often has to satisfy a number of events before deplying an airbag. These could include speed, deceleration, crush zones being compromised.

By the looks of the discovery, it looks like the crush didn't reach the sensor. On my P38, they sit a few inches behind the light cluster on the chassis rail. That discovery doesn't look like the crush has gone further than the light cluster . . . so the switch was probably never triggered.

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They are designed to work with a car's crumple zones and to inflate the cars airbags at an optimum time. Without altering ECU there is no way an HD bumper manufacture could mimic the characteristics of the standard bumper. However, some maintain OEM crash cans on front of chassis to try and go some way towards this, however, I see this as pointless as you've now introduced a weak point to a front 'HD' bumper.

So did I Steve until I saw a Disco II fitted with an ARB bumper that hit a concrete bollard at speed (enough to totally destroy the bollard). The bumper had been bent a little and the crush cans needed replacing but the chassis and bodywork were undamaged - this wouldn't have been the case if the vehicle didn't have an HD bumper.

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