Air spring design faulty

[oscjam]

Hi All,

I have made an interesting, if not startling, discovery with regards to the Arnott replacement front air springs for the Allroad.

After the OEM's air springs failed on my vehicle I purchased the Arnott front air springs.

Over a period of 4 years and 50000 miles the vehicle has been through no less than 5 Arnott air springs. All the air springs failed suddenly. The car would be fine one day and the next day it would drop right down within a matter of minutes and the air springs would then need to be replaced. , i.e. no slow leak type scenario's.

When the last one failed I noticed that the vehicle was resting on the control arms and the vehicle was not driveable as the wheels would rub against the arches when the steering is turned.

The air spring airlines also got damaged in the process as they got pinched by the control arms pressing them against the fender.

This seemed strange to me as I did not experience this when the OEM air springs failed and was able to still drive the car to a workshop or home.

I ordered a new Arnott air spring and upon closer inspection established that the bump stop in the Arnott air sping is 40% shorter (60 mm long) vs the OEM bump stop (100mm long).

This explains why the vehicle was resting on the control arms as the Arnott bump stop is not long enough to support the load of the vehicle which is what it is supposed to do.

More alarming is the fact that the bump stop is a very important safety component that is designed to ensure the vehicle remains stable on the road when the suspension is under maximum compression. If during hard cornering the bump stop does not support the side under compression it can cause instability and an unpredictable behaviour of the vehicle which can cause the driver to lose control.

Even worse imagine a scenario where an air spring fails during high speed cornering resulting in the wheel rubbing against the fender. This can induce a sudden oversteer and resultant loss of control of the vehicle.

I also believe the sudden failures I have had are a result of the air spring having to do many more high compress cycles than it should due to the fact that it does not have an adequate bump stop to support it. See pic of failed air bellow reflecting the catastrophic failure!

I have enquired with Arnott about this alarming design fault. They have however not even bothered to revert with an explanation.

I sent the Arnott air spring back as it is clearly not fit for purpose.

I would be interested to hear what other peoples experiences have been on this.

[Steve Q]

Wow! Those findings are alarming! What it shows is that you can't beat OEM components. I wonder if it's worth you contacting Which? Or watchdog to see if they'll investigate. 

Cheers

Steve