Quick question: AHC...I can see the advantage of raising the vehicle, but what advantage is there in lowering it? (1 Viewer)

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Lower setting helps with high-speed maneuvering. One, less wind resistance. Getting air up into the underbody creates all sorts of drag and issues. Look at NASCAR and F-1 cars and see how snug to the ground they are. That's not just to look cool...

Also, lowering even an inch or two changes your center of mass. If you're trucking along at 70-80 mph, that change in center of mass/center of gravity can mean more stability. This affects how it handles in high winds, cornering, and well, just handling in general.

I mean, think of it in the reverse.... what do you really gain with a 2" lift? Handling changes, yes, but so do clearance, clearance angles. And depending on the situation, that 1-2" could be the difference between just rolling merrily along a rutted trail versus a no-go.
 
Except you're unable to drive in "LOW" above 20-25MPH unless you've overridden it in the computer.

Also, have you driven in the low setting? It feels terrible like it's bouncing off the bump stops.

Lift won't do anything on its own on a trail. The lift is just to accommodate bigger tires, which are what actually make the difference. Lift on stock tires = no improvement other than approach angles.
 
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my mother in Law really apricated that this truck is low compare to my others. I didn't bother to Explain AHC to her, but she definitely apricated the ease getting in and out.
 
All listed reasons are great, personal experience hooking up trailers, entry into garage with cargo carrier on top, entry/exit for older folks, servicing engine. To echo others input you cannot drive at speed in low.

Our 570 has a Entry/Exit button that when is on automatically lowers when the car is turned off. Love this.
 
I don't have a ton of experience with AHC. Myself, I don't like or want. I'm a believer in the KISS Principle when it comes to things like that. I've heard good things about said systems, particularly on Land Rovers... but their reliability isn't all that and a bag of chips anyway. So, was not aware of speed restrictions.... so, sounds like it was installed for access purposes.... which, yay for soccer moms. My experience with LC 100's is minimal (just bought one to start building up.... so....), and I'm here to learn.

As for lift.... wow. Nitpick much? Here, I'll be more specific.... a lift, with larger tires, as generally a lift is done to accommodate larger tires, generally allows for greater approach/departure/breakover angles and can improve articulation as well as clearance. Your results may vary. There. Better?

Main point was to simply address benefits of control of ride height from a very general standpoint. There are other vehicles with adjustable suspension systems where lowering, even a small amount, is done for changes in handling and driving style.
 
Firstly, let's not compare the LandRover systems to the Toyota/Lexus AHC. The LandRover systems are notoriously finicky and prone to failure. The AHC system is considerably overbuilt and, when maintained properly, can handle a ton (technically 3.5 tons) and do so reliably and capably. The problem for our systems is that most, if not all, are bought 2nd hand or even 3rd hand. They are as much as 21 years old too. Previous owners may or may not have maintained the system. They may have maintained it, but not properly. I doubt many ever flushed and refilled the system on schedule. Heck, even some Toyota dealerships don't understand it. Having cut mine open after removing it, I can say this: AHC is a very well designed and robust system. I wheeled a decently equipped LX over every major pass in CO, NM and tooled around Big Bend National and State Parks with nary an issue. I trusted it like I trusted the rest of my LandCruiser/LX. Ultimately, I removed mine because it, like any suspension, had reached the end of it's effective life. Mine was 20 years old at the time of removal and had nearly 180,000 miles. That means that the springs (TBs and Coils) had lost much of their spring rate. The globes were starting to show signs of difficulty maintaining pressure. And, finally, I was taking my rig 1100lbs over stock. Think of it this way, even super nice Icon Stage IIIs require rebuilding multiple times to reach 20 years and 180,000 miles. Very few conventional systems can rival the longevity of properly maintained AHC system. The key element there is "properly maintained".

Definitely correct in the sense that the only way to truly increase ground clearance (at the axle) is via larger tires. I see F350s jacked to the sky, but with 33" tires. As a consequence, they have the same ground clearance as I do on my 33"s. Their approach/departure angles are slightly better and they are less likely to damage a rocker panel since the body is lifted so high. But, their axles can only clear the same things mine can.

The AHC does lower a little at speed (improved handling and aerodynamics....laughable at our mpg) and raises a little automatically when 4LO is engaged. The general concept of AHC was so the you could lower the vehicle to ease entry (important for small children and short wives/girlfriends) and raise the vehicle to enhance tire clearance to the fender when articulating off-road. The high setting has a speed limitation of no more than 20mph before it auto lowers to normal. Clearly designed with off-road in mind. Again, simply to provide a little more ground clearance for the body (specifically the factory side-steps) and mitigate wheel rub with the fenders when articulating off-road. The vehicle has a 0mph speed limitation in Low which means it will automatically raise once the vehicle moves even the slightest. Slee makes a lockout that allows you to prevent the auto-raise/lower. I had that and liked it. Driving in Low would be absolutely awful. It's effectively sitting on the bumpstops in Low. Again, great for ingress/egress of passengers and handy for entering low garage overhangs (if the Slee lockout is installed). But, driving at any speed in low would be incredibly uncomfortable.

I agree with the KISS concept. AHC is a system that takes knowledge and some consistent effort to keep in balance. Once I started taking my rig into the wild and added all the bells and whistles, a conventional upgraded suspension made more sense. However, I do miss the AHC ride quality (adjustable at that) and the ability to raise/lower on command to address issues as mentioned above.
 
I have never seen any evidence that the vehicle actually lowers any at speed to improve mpg and aerodynamics. I have always suspected this was a myth.
 
@geanes Good stuff to know. The 2005 I snagged recently doesn't have AHC, which made me happy. I just always have issues with adding the complexity of AHC to a vehicle. Sure, when it works, it's great. But I'd imagine field repairs are going to be a nightmare, and WILL necessitate a visit to Toyota. Just, it's more more thing to seriously go wrong that I'd prefer to not deal with.

@68W65D some of the newer Cadillac sedans have mag suspensions that are adjustable for driving styles. Mercedes too, iirc. There's probably others, but there's vehicles that have "sport" mode with those systems that do adjust ride height, tighten up the suspension, etc. More to do with handling than anything else.... but you gain a small advantage on aerodynamics, which can increase mpg (which, is likely being wiped out if driving aggressively).
 
@68W65D some of the newer Cadillac sedans have mag suspensions that are adjustable for driving styles. Mercedes too, iirc. There's probably others, but there's vehicles that have "sport" mode with those systems that do adjust ride height, tighten up the suspension, etc. More to do with handling than anything else.... but you gain a small advantage on aerodynamics, which can increase mpg (which, is likely being wiped out if driving aggressively).

I get the concept. What I am saying is that I have never seen any actual evidence that the LX470 automatically lowers any when driving above a certain speed.
 
I have never seen any evidence that the vehicle actually lowers any at speed to improve mpg and aerodynamics. I have always suspected this was a myth.

Mostly noticeable when you come to a stop. You'll then feel the suspension raise just a little. It's a very small amount. The system also cross-levels while in motion so you and your passengers stay level....to a degree (no pun intended). The AHC definitely isn't as aggressive as those systems in LandRovers which practically slam the vehicle down at highway speed. It's really only a few mms (in the 570, it lowers an inch in the front and 3/4inch in the rear at highway speed) in the AHC and not really sure how much, if any, improvement there would be in mpg. Maybe just a little more stable.
 
Here is another benefit of AHC, it self-levels for loads. Here is another video outlining the self-lowering at speed....
 
Technically, what controlled that was the AVS (Adaptive Variable Suspension) which first showed up in the 80's as the TEMS (Toyota Electronic Modulated Suspension). Was also known as Skyhook TEMS. The later LX570 was more aggressive in it's self-lowering at speed. But, the 470 would do it a little along with self-modulating dampening at each corner independently at different speeds, road conditions and vehicle lean. It would mitigate brake dive and acceleration squat as well leading to a more stable experience.
 
I get the concept. What I am saying is that I have never seen any actual evidence that the LX470 automatically lowers any when driving above a certain speed.

I have seen it many times in my oldie.. self levels when coming to stop (at signal) or at startup. Once I have loaded all the way up (8 passengers and definitely none were < 150 #'s each) it went to low mode on the freeway
 
I have seen it many times in my oldie.. self levels when coming to stop (at signal) or at startup. Once I have loaded all the way up (8 passengers and definitely none were < 150 #'s each) it went to low mode on the freeway

That is usually a condition of worn springs or even a worn AHC system (possibly both). It will "scram" into Low if the load exceeds its capacity. Kind of a fail-safe/protection mode. It could handle the GVWR of 6800lbs easily (mine certainly did and I was at 7000lbs on the button). Anything above that and you'd have issues in even a brand new AHC system if you haven't upgraded the springs/coils to something like the King Springs. As great as AHC is, it has it's limits. Then again, you wouldn't want to run a heavily laden rig on OME medium springs either or OEM Toyota springs. Load an LC to 7600lbs without changing the springs and you'll have the same experience as AHC Low (maybe even blowing up the shocks). Matching the suspension to the weight is critical. Difference with AHC is that you have a wider delta (as long as you upgrade the springs and properly maintain the AHC hydraulics).

Curb weight of an LX470 is 5401 lbs. GVWR is 6856 lbs. That means you have a delta of 1455 lbs. 8 passengers at an average of 120lbs would be 960lbs. That leaves 495 lbs for gear and equipment. If each person brought 20lbs (fairly light in most circumstances) of gear, that's another 160lbs. If those people weighed an average of 140 lbs (still very light for us Americans) that would add yet another 160 lbs. Now you are within 170 lbs of max GVWR. As you can see, it's well within reason to overload the suspension. Just as you could overload a conventional suspension with the wrong springs (too light).

As the AHC (or any suspension for that matter) ages, springs lose their lifting capacity. Over the course of 12-21 years (covering the 100 series production cycle), those springs could lose 2-5% of their capacity (maybe more). That means you lose as much as 340 lbs of capacity (not insignificant). Again, any suspension with age and use will decline. The AHC is unique in that the coils/tbs functionally handle about 60% of the weight (conventional systems the springs handle ALL the weight) and the AHC element handles the 40% balance. So, in an AHC system, you're dealing with two wear/age variables (the springs themselves losing their lift and the AHC globes wearing which reduces their lift capacity). In a conventional system you're really only dealing with one variable, the springs themselves (the shocks simply dampen the springs).
 
Our Model S does roughly the same thing as Toyotas AHC. You can set the ride height, low, medium, high, or auto. At highway speeds it actually lowers automatically to improve stability, and be more aerodynamic.
 
I don't have a ton of experience with AHC. Myself, I don't like or want. I'm a believer in the KISS Principle when it comes to things like that. I've heard good things about said systems, particularly on Land Rovers... but their reliability isn't all that and a bag of chips anyway. So, was not aware of speed restrictions.... so, sounds like it was installed for access purposes.... which, yay for soccer moms. My experience with LC 100's is minimal (just bought one to start building up.... so....), and I'm here to learn.

As for lift.... wow. Nitpick much? Here, I'll be more specific.... a lift, with larger tires, as generally a lift is done to accommodate larger tires, generally allows for greater approach/departure/breakover angles and can improve articulation as well as clearance. Your results may vary. There. Better?

Main point was to simply address benefits of control of ride height from a very general standpoint. There are other vehicles with adjustable suspension systems where lowering, even a small amount, is done for changes in handling and driving style.

Sorry, my intent wasn't to nitpick, just point something out based on info you admittedly didn't have yet. If you're talking about putting larger tires on an AHC equipped vehicle, then you'd still need to override the computer or physically modify the sensors to accommodate the tires (both are easy). Meaning, in a discussion about a factory AHC system, bigger tires still aren't really a consideration outside of what any stock-height 100 series could run without lift. Yes you can keep the vehicle in the high mode as long as you stay under 20mph on a trail, but you're still going to be limited to whatever tires are going to get you to the trail on an otherwise stock-height vehicle (again, unless modified).
 

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