Lets settle a few myths about airbags.
Author: Jack Date Posted:18 October 2017
Its time to settle some common misconceptions about airbags (the load assist kind, not the hit you in the face when you crash kind).
We see it all the time, somebody will ask about fitting airbags to their vehicle and they are bamboozled with a dozen uneducated responses of "Airbags will cause your chassis to bend". Let's settle a couple of myths.
"Airbags put the load where it isn't meant to go"
This is the most common response to the age-old airbag question. This is a bit of a two-part answer.
Firstly, on leaf spring airbag kits, the bumpstop is removed and replaced with the airbag. Where the bumpstop is mounted is one of the most reinforced parts of the chassis, this is because it is designed to take a large impact and sharp jolt directly on it from the bump stop. When replacing the bump stop with the airbag, the sharp jolt is replaced with a cushioning progressive load application. This progressive load application is a lot more forgiving on the chassis as there are fewer sharp impacts on the chassis.
Secondly, when fitting the airbag, you aren't moving all of the load from the leaf springs to the airbag, but you are sharing the load and weight of the vehicle across 3 points, instead of the 2 points with leaf springs only. Airbag Man have gone the extra mile with this, by hiring an independent engineer to assess & measure the stress on a chassis fitted with and without airbags. With the fitment of airbags to the vehicle, amazingly the chassis was under less stress than without airbags fitted! Make sure to have a look at the image at the bottom of this page to read this independent engineering analysis.
The points above are for a leaf sprung vehicle, on a coil sprung vehicle, the airbag is fitted inside the coil spring and is applying the load to the exact same location as the coil springs. Simply put, the chassis will be under the same load with or without fitting airbags to the vehicle.
"But some of the vehicles I see with a bent chassis have airbags fitted"
This may be true, but it is obvious the placement of the airbag is not causing the chassis to bend. Every vehicle that I have seen (both in person and in picture) has had the bend in the chassis in front of the axle, and usually on or around the kick in the chassis behind the cab. This is because the location of the kick in the chassis (which is there to raise the chassis up to maintain proper axle-chassis clearance) is a weaker part of the chassis.
If the airbag was going to cause a bend in the chassis due to where the load is being applied, you would expect the airbag to be the fulcrum or pivot point, and the chassis behind the airbag would be the bend location.
"Well, why do these vehicles bend?"
Every vehicle has the following maximum weights it must stay under:
- GVM - The maximum the vehicle can weigh
- GCM - The maximum the vehicle and its trailer can weigh (together)
- Towball Weight - The maximum download that can be applied to the towball.
Every vehicle manufacturer sets these guidelines with the vehicle's handling, suspension, braking and most importantly the vehicle's chassis. These weights are tested & applied by the manufacturer on bitumen, with offroading usually forgotten about. When you are offroad, or on the beach, the vehicle's chassis is under a lot more stress with every large washout or jolt.
When a vehicle is overloaded (over GVM, GVM or Max towball weight) the vehicle's chassis is under extreme stress, and with a large jolt from a washout, it is a recipe for a bent chassis.
"So what does an overloaded chassis have in common with airbags"
Without airbags fitted to a vehicle, it is very easy to see that it is overloaded, the suspension is heavily sagged down and it looks extremely heavy.
A lot of drivers will now see that the vehicle is sagged, fit airbags and pump them up until the vehicle is sitting level. They now feel that because the vehicle is sitting level that there are no issues, but the chassis is overloaded and failure is imminent.
"So how can I be sure that my chassis will not bend"
Its easy, Stay within the weight guidelines for the vehicle.
The airbags do not cause any negative effects on the chassis, but will give you a false sense of security by thinking that because your overloaded vehicle is sitting level, it is fine.
Airbags are fine to use on all vehicles, but when using airbags, use your head and remember the weight guidelines set out by the manufacturer.
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