Airing down was raised again, on a recent post.

Consider a 35 mph drive on a rutted, washboard, muddy, off-road trail somewhere remote and untended. I have attached a link to a good summary of active suspension design modeling -- which is what we have on the New Defender -- provided by the air suspension and variable viscosity (magnetorheological) dampers.

https://www.sciencedirect.com/topics...ive-suspension https://en.wikipedia.org/wiki/Magnetorheological_damper



standard active suspension model - Kt and Bt and some of the mu (unsprung mass) are provided by the tire

Airing down the tire or going to a stiff / heavy off-road tire will modify the spring (Kt) and damping (Bt) constants of the tire. These actions are not captured by the logic in the computer and so will throw off the algorithm for the suspension system.

My only wondering is to see how much difference could a 20+ psi reduction in a heavier, off-road tire make in system effectiveness?

I will keep looking .......

Enjoy !!

 

I'll be interested to hear what you find.

As I've mentioned in some of these threads we make multiple trips each year to an OBX beach house that is located in the 4x4 section of Corolla. This means driving up and down the beach and across the dunes daily.

County regulations REQUIRE people to air down below 20 psi to drive in this area. Though it's quite obvious from the dozens of people we encounter stuck in any give week that it is not strictly enforced.

Since we run to town often in any given week (only a few miles of pavement, 35 mph or slower) we tend to air down into the low 20's but not all the way below 20 so that we can cheat it a bit and not air-up each and every time we run to the grocery store or a restaurant.

I'm curious if there's "safer" or "better" threshold.

The P400 110 makes short work of the sand and I'm quite happy with it, even in the low 20s. But if a few more psi would better protect the tire or work better with the suspension then I can adjust me deflators and run a little more pressure. As long as I don't get stuck no one will care.

 

We really enjoy going to see the wild horse herd. Great Fun in Corolla!

 

Over the years we see them pretty much ever day we're down there...

 

I know nothing about the suspension magic going on down below but do know that running an E rated KO2 at full load PSI (~50psi) over corrugations was nowhere near comfortable.

Your very bones get shaken loose from their sockets. Can't be good for the car.

Lowered to ~35psi and all was well.

The way I see it, the more bumps the tires can fold themselves over, the less the mechanical suspension needs to do, regardless of how much electrical whizz-bang in play.
A smoother ride, more traction viz-a-viz a longer footprint and greatly reduced stress on the drive-train are laudable byproducts of airing down.

Most of LR product promos and aftermarket customer education via the JLR experience, all seem to be on lovely wide open hard pack sand/muddy/grassy/gravelly terrain. Airing down is probably not so important here, or wise where 20" rims abound. A very different world to my playground around here.

Perhaps it relates more to my inexperience, but being able to take air out and have tires that can bend and fold around various objects has been a complete game changer.

I know this is just anecdotal BS from a novice, doesn't really speak to the technical nature of the OP's post but I think sometimes we can get lost in the technical weeds. I just don't see any merit to not airing down assuming the right tires and rims are in effect. The benefits to driver and vehicle are clear as day.

 

I'm very interested in this as I've never driven on the beach in my life yet I'm eagerly looking forward to it with the 130. I watch a lot of Ronny Dahl (I know I'll never do that type off roading) and it seems like there's always an emphasis on airing down below 20psi on the beach so the tire can "spread out" across the sand. I don't see how the car's electronic systems can get over that need to spread out more.

 

I don't watch a lot of You-Boob reviewers, but I did see a bunch of them when the Defender first came out. One of the oft-repeated themes was that they didn't understand WHERE it was finding the traction (sometimes deep mud, sometimes snow, sometimes sand) but it was.

I have pulled, dug, de-aired dozens of stuck people on the beach in the OBX over the years, and yeah, de-airing is a thing. But between The Insider's advice and my own experience wanting to keep pressures up a bit, I can confirm the Defender just makes EASY work of it. The locking diffs and torque vectoring with brakes and whatever else just keeps it moving effortlessly. My Wrangler is a tough little truck, and it gets the job down too, but it literally feels different. Like the Wrangler is working harder to do it, even at the same or lower tire pressures.

* shrugs *

 

My favorite was someone in Australia I think it was, they were trying to go up a big sand dune. They took off, got stuck, started bitching and moaning about the design and then looked at the 4x4 menu and put it in sand mode and it walked right up the same hill, and then they proceeded complain that was a problem because it should just work like solid axel vehicles do.

The only thing I question on the Defender these days is the 20" wheels and no 35" option without massive modification, I can see clear reasons why 35s would be wanted in the west half of the US as the pinching between rim and rock seems pretty clear and I don't know an option around that other than 'more sidewall', but I'm a newbie in offroad driving too.

 

Yeah, that was Ronnie Dahl. He actually is very capable and a good teacher and a clear sharer of important things for an off-road driver to know. I have learned much from his videos (amongst learning from others). But, he is pure old-school and has not put in the time to understand how his driving approach needs to change to make the new technology effective.

I think some of the new-school capability practically disables the ability to heavily modify the New Defender, as some of the computer logic cannot adapt to such significant changes. This is one of the reasons I think that Sarek went with coil suspension, instead of active air bags.

Enjoy !

 

My wife and I enjoy seeing the wild horses as well! We've only been in our Jeep JLU Rubicon though.
I'm still patiently waiting for our Defender 110 X to be built on 11/18. This will be our first JLR vehicle and we can't wait to try it out in OBX!