The primary issue for EAS is lack of PM.
On the LR3/4, the truck will auto level every 20 minutes once it's shut off. If you have a leak (in the bag, blocks, lines, etc), the truck will lower on one corner, then level. Then lower again, then level. Pretty soon you're on the bump stops.
If you don't address these concerns, your compressor will be running all the time, which can lead to a failure due to overheating, especially when at offroad height when more air is needed to keep the bags full. If you run a stupid set of johnson rods, this will be accelerated as you'll be over-height the whole time with the compressor running nonstop.
The 2nd issue is that many people ignore the fitment of oversize tires with EAS. I run a 265/65/18 tire, which I've verified to clear at full lock even with the bags complete deflated. If you run a larger tire, you could see an EAS failure and not even be able to get moving on flat ground.
Paranoid (prepared?) people will also add a valve to the top of the airbags to be able to air them up with a standard compressor. This could help you in the event of a compressor failure on the trail.
Air Suspension has a bad wrap because it was problematic early on when introduced into production vehicles, but most of the lessons have been learned the hard way and long ago resolved with today's air suspension systems.. for example the infamous Audi Allroad was one of the first, and always had problems.. mostly because if it sprung a leak, it'd run the compressor at full duty cycle, which its not rated for.. and burn it up.. now you have a leak and need a new pump.. However on mine, its got time out timer and thermal monitoring on the air compressor.. it wont run the pump until it fails anymore.. Other issues were with corrosion and stuff, air fittings w/poor metallurgy that would corrode and then snap, requiring a whole new strut (expensive).. the check valves now on the struts are really easy to service, wont weld them selves to the strut.. are cheap and easy to replace if one gets stuck.. most of the problems with air suspension were not with struts themselves, but with check valves, distribution blocks, air hoses.. and after a couple of decades the engineers have worked out most of the longterm issues with that "complexity"..
The only issues I really hear of anymore are intermittent stuck valves, and usually only in really cold temps.. indicating there is some moisture in the line and the valves are freezing shut.. I live in a really dry climate so I've never had that issue.
Thank you both for these answers. That is very informative. My thinking has evolved on this topic, and my takeaway is that Air Suspension represents a unique challenge with a vehicle, but the problems you folks had identified appear to be manageable. Every vehicle has unique challenges of varying degrees, and depending on the application those challenges might not matter, or they might matter a great deal. The alleged complexity of these systems doesn’t seem to be as big of a deal as I thought, especially with Blaise’s point of installing valves and inflating ‘manually’ with a compressor, and Dreadlocks’ point about how long these systems have been in use and what has been done to address the common failures. Traditional suspension would have gone through a similar process.
If the Defender uses the same air bags at every wheel (Maybe they all do, I don’t know) it will help. That way, one spare bag on hand might be enough in case of a rupture, and in the event of component failure you can just blow up the balloon with your external valve. I dare say that seems like an easy problem to fix, and depending on the process, I can see this being even easier than dealing with a broken leaf or coil. Ease of roadside repair matters a lot to me — I don’t see reliability as ‘never breaking’; the nature of Overlanding means stuff will get roughed up and worn out and eventually you need to turn a wrench or — certainly for any rig built in the last 15 years or so, not just JLR cars — boot up the laptop. I see reliability as at least partly “rely on it to get you home”, so that is where the ease of trail-side repairs matters.
Of course the other perspective is
frequency of that repair needing to be done. Nobody wants to have to fix the same problem over and over. I know there are a million anecdotes about Air Suspension failures, which suggests these fail often. But those anecdotes get repeated a lot by people who sometimes don’t have experience with airbags, as many negative experiences are amplified quite a bit online. Positive anecdotes tend to be whispers on the wind (hot air?
) that is the internet in comparison to the negative ones.
Regardless, positive or negative anecdotes only paint part of the picture. I’d really like someone to take 10, 20, 100, or 1,000 Rovers with air suspension, and an equal number of Jeeps with Coils, and maybe an equal number of rigs with leaf springs, and put them through the same sets of real-world tests until failure so there can be some aggregate data. If this data exists and is recent I’d love to see it. It’s hard to beat the conceptual simplicity of metal springs, and I think there’s a lot of wisdom there — but air bags maybe aren’t the serious deal breaker I initially thought they were.
Thanks for the information, folks. Much appreciated learning about this today!