AHC: what are the pros/cons? (1 Viewer)

[jumptrader]

2003 LX470 - 110,000 miles

I've been researching the AHC to better understand its function, and as far as I can tell the main advantages are:

1. Lower height for ease of access
2. Raise height for ground clearance
3. *Partially* lower the height during highway speeds
4. Auto-level the vehicle with new loads (passenger, cargo)

The cons to system seem to be mainly:

1. Costly to fix
2. If damaged, can produce a bumpy and rough ride

My questions:

1. Am I missing a function of the AHC? Is there anything *actively* it is doing during the ride to introduce comfort? Besides point #3 above? Otherwise in terms of active ride comfort, that seems to be covered by the AVS system.
2. Are busted accumulators more or less comfortable than a conversion to springs?

Thank you!

 

[Higgin]

Looks like you are mostly right with what you have said. What I'm seeing that looks incorrect is the *partially* lowering of the height during highway speeds. Here's how ride height works in stock form.....There is a low height, a neutral height, and a high height. Neutral is the normal, default height for most driving situations. The low setting only works at less than 5mph I believe. Its meant for loading/unloading cargo/people when the vehicle is not moving. Once you start moving, truck goes back to neutral automatically. High is meant for offroad situations where extra ground clearance is needed. Once you get past 30mph I think, the truck will automatically go back to the neutral setting. As far as I know, when you are driving highway speeds, it just stays in the normal "neutral" height. I'm pretty certain it does not lower any at speed. It does auto level as you mentioned.....I tow a 12 foot trailer with my side by side atv often and thats where I really like the AHC because once I load up and start the engine, the AHC levels everything out to where it should be so my lights aren't shining up into the trees,etc. You also get the 4 place selector that adjusts the suspension dampening. It has comfort to the left (softer dampening, most body roll), and sport to the right (very stiff dampening, least body roll) and 2 spots in between. I find the #3 spot is usually where I keep it most days unless the g/f is riding along, she likes the comfort setting. Personally, I like the AHC system, but if I wasn't towing at all, it would not be worth the risk of a possible expensive failure down the road. But, after searching for a nice Land Cruiser for many, many months and not being able to find a good one, I ended up buying a nice LX470, so I had no choice in the AHC matter I'll use it and enjoy it as long as nothing breaks, but if it ever does, I'll probably swap in the regular springs from the Land Cruiser.

Hope I didn't confuse you even more, I'm sure other will be along to help explain, but it sounds like you have it pretty much figured out.

 

[guardcompany]

For me it was simple...

Goal: offroad/expo/overland rig? Then no AHC! No matter what the AHC fan boys will say it will costs more long term if that is the purpose for your rig.

Goal: general family/adventure/towing rig? Then AHC is a good choice given the system has been maintained and the miles are lower. Lots of trails you can go with AHC in High.

Personally I was looking for a offroad rig and not a daily driver and I didn't want AHC as I saw it as a temporary solution I would have to replace at one point. However there are many members on here that have the AHC Slee mod and run some hardcore trails.

Your mileage may vary.

 

[uHu]

...the main advantages are:

1. Lower height for ease of access
2. Raise height for ground clearance
3. *Partially* lower the height during highway speeds
4. Auto-level the vehicle with new loads (passenger, cargo)

The cons to system seem to be mainly:

1. Costly to fix
2. If damaged, can produce a bumpy and rough ride

My questions:

1. Am I missing a function of the AHC? Is there anything *actively* it is doing during the ride to introduce comfort? Besides point #3 above? Otherwise in terms of active ride comfort, that seems to be covered by the AVS system.
2. Are busted accumulators more or less comfortable than a conversion to springs?

In addition to the Pros it also adjusts damping according to road conditions, limits roll in curves and squat/nose-dive during acceleration and braking. Washboards is one condition where the AHC/TEMS excels.
As said above here, there is no lowering during highway speed, but there is an extra high, which adds an inch over the high setting when the "offroad" gets rough. If you drive in the low range (transfer case Low), the ahc does not go down to Normal height automatically at any speed, if you have put it in High.

As the ahc helps with body roll, the stabilizer bars on an ahc-version 100 series are weaker than on one with conventional suspension. That means you have a more comfy suspension system on normal, flat roads. Then the ahc/tems will help stiffening things up when the need arises, by increasing damping, closing off left-right hydro connection (to prevent roll), and preventing squat and dive. The system uses input from steering angle, brakes, accelerator, speed and individual wheel speed; and from the height sensors it reads both the height and any rapid changes in height due to road conditons.

Busted accumulators (aka globes, spheres, gas springs) are definitely less comfy than anything else. you will have no springs at all, all rigid, as the system is completely hydrolocked, if all 4 globes are completely busted. The only give/suspension you have is in the tires. Low-Normal-High will still work tho'.

 

[jumptrader]

In addition to the Pros it also adjusts damping according to road conditions, limits roll in curves and squat/nose-dive during acceleration and braking. Washboards is one condition where the AHC/TEMS excels.

Are you describing the AVS system? And does the AVS system utilize the AHC hardware? As in, if the AHC is removed, then the LX470 wouldn't have AVS.

Thank you

 

[Kabanstva]

What's the fastest you can drive with the AHC setting in "high" Does it automatically drop down to "n" after a certain speed?

What about the low setting, does it raise the truck after a certain MPH?

 

[uHu]

Are you describing the AVS system? And does the AVS system utilize the AHC hardware? As in, if the AHC is removed, then the LX470 wouldn't have AVS.
Thank you

On the cruiser, the AVS is named TEMS, and is an integral part of the AHC (or maybe ahc is a "side effect" of TEMS):

Toyota Electronic Modulated Suspension
From Wikipedia, the free encyclopedia
TEMS (Toyota Electronic Modulated Suspension) was a shock absorber that was electronically controlled (Continuous Damping Control) based on multiple factors, and was built and exclusively used by Toyota for selected products during the 1980s and 1990s (first introduced on the Toyota Soarer in 1983[1]). The semi-active suspension system was widely used on luxury and top sport trim packages on most of Toyota’s products sold internationally. Its popularity fell after the “bubble economy” as it was seen as an unnecessary expense to purchase and maintain, and remained in use on luxury or high performance sports cars.

Summary
TEMS consisted of four shock absorbers mounted at all four wheels, and could be used in either an automatic or driver selected mode based on the installation of the system used. The technology was installed on top-level Toyota products with four wheel independent suspension, labeled PEGASUS (Precision Engineered Geometrically Advanced SUSpension). Because of the nature of the technology, TEMS was installed on vehicles with front and rear independent suspensions.

Based on road conditions, the system would increase or decrease ride damping force for particular situations. The TEMS system was easily installed to suit ride comfort, and road handling stability on small suspensions, adding a level of ride modification found on larger, more expensive luxury vehicles. The technology was originally developed and calibrated for Japanese driving conditions due to Japanese speed limits, but was adapted for international driving conditions with later revisions.

As the Japanese recession of the early 1990s began to take effect, the system was seen as an unnecessary expense as buyers were less inclined to purchase products and services seen as “luxury” and more focused on basic needs. TEMS installation was still achieved on vehicles that were considered luxurious, like the Toyota Crown, Toyota Century, Toyota Windom, and the Toyota Supra and Toyota Soarer sports cars.

Recently the technology has been installed on luxury minivans like the Toyota Alphard, Toyota Noah and the Toyota Voxy. The TEMS system has been recently named “Piezo TEMS”, “Skyhook TEMS” “Infinity TEMS” and more recently “AVS” (Adaptive Variable Suspension).

 

[jumptrader]

On the cruiser, the AVS is named TEMS, and is an integral part of the AHC (or maybe ahc is a "side effect" of TEMS):

Got it. Thank you!

 

[planomateo]

What's the fastest you can drive with the AHC setting in "high" Does it automatically drop down to "n" after a certain speed?

What about the low setting, does it raise the truck after a certain MPH?

 

[geanes]

I like the AHC system bunches and bunches and will be sad when mine stops working. I like that I can lower the system to get the truck in the garage (STUPID 7' garage doors on new homes) and to unload cargo. I like that I can raise it higher to cross creeks, etc. The vehicle does lower slightly at highway speed to increase efficiency (absurd concept on a 13mpg vehicle) and even has an "extreme" high setting that it can go to in certain offroad situations. I have the Slee AHC override switch installed which allows me to bypass the auto-settings (I can drive at any speed in any height). I needed that so I could drive the rig in Low into my garage without it automatically lifting as I backed in. When flushed and adjusted correctly, it rides like a Cadillac that's actually reliable. I'm putting AirBags in my rear coils so I can adjust the springs for different loads.

In the end, I won't invest in replacing it with AHC when it ultimately fails as that can get very costly (shocks, spings, globes, etc) I'll switch to an IronMan ProFoam at that point. The way I see it is that once one component fails, others are going to as well. Replacing each component as it fails just doesn't seem financially smart.

 

[PabloCruise]

I think it is the 570 (200 series) that will lower at highway speed.

 

[Cubiclegangsta]

Looks like you are mostly right with what you have said. What I'm seeing that looks incorrect is the *partially* lowering of the height during highway speeds. Here's how ride height works in stock form.....There is a low height, a neutral height, and a high height. Neutral is the normal, default height for most driving situations. The low setting only works at less than 5mph I believe. Its meant for loading/unloading cargo/people when the vehicle is not moving. Once you start moving, truck goes back to neutral automatically. High is meant for offroad situations where extra ground clearance is needed. Once you get past 30mph I think, the truck will automatically go back to the neutral setting. As far as I know, when you are driving highway speeds, it just stays in the normal "neutral" height. I'm pretty certain it does not lower any at speed. It does auto level as you mentioned.....I tow a 12 foot trailer with my side by side atv often and thats where I really like the AHC because once I load up and start the engine, the AHC levels everything out to where it should be so my lights aren't shining up into the trees,etc. You also get the 4 place selector that adjusts the suspension dampening. It has comfort to the left (softer dampening, most body roll), and sport to the right (very stiff dampening, least body roll) and 2 spots in between. I find the #3 spot is usually where I keep it most days unless the g/f is riding along, she likes the comfort setting. Personally, I like the AHC system, but if I wasn't towing at all, it would not be worth the risk of a possible expensive failure down the road. But, after searching for a nice Land Cruiser for many, many months and not being able to find a good one, I ended up buying a nice LX470, so I had no choice in the AHC matter I'll use it and enjoy it as long as nothing breaks, but if it ever does, I'll probably swap in the regular springs from the Land Cruiser.

Hope I didn't confuse you even more, I'm sure other will be along to help explain, but it sounds like you have it pretty much figured out.

We’re AHCs optional? If they were standard, what years?

 

[planomateo]

We’re AHCs optional? If they were standard, what years?

Standard on LX, added to Land Cruiser as optional 2006-2007.

 

[nothappening]

We’re AHCs optional? If they were standard, what years?

I think for Lexus it was standard all years. For Land Cruiser it became standard in continental US in 2006 and 2007. Of course, there are a small number of exceptions and different countries have different options.

I always heard 9 mph as max for Low, and 19 mph max for high.

Edit: Someone beat me to it, I assumed it was standardized in '06-'07 but I guess it was just optional.

 

[flintknapper]

I think for Lexus it was standard all years. For Land Cruiser it became standard in continental US in 2006 and 2007. Of course, there are a small number of exceptions and different countries have different options.

I always heard 9 mph as max for Low, and 19 mph max for high.

Edit: Someone beat me to it, I assumed it was standardized in '06-'07 but I guess it was just optional.

 

[Stevehats]

Last year I went on a trip where we traveled from New Mexico to Colorado on primarily Forest service roads. I did this with AHC as mine was in great condition. My pressures and graduations were where they needed to be. We loaded up for the 10 day trip and the AHC leveled itself and handled the weight of the load very well. We even went on some very rough roads that had completely washed out. My problem with the AHC is that in order to put it in High you have to put it in park and wait until it has risen into high. This became very tedious because any time you reached that 20 MPH it would lower. I then would have to rinse and repeat. On roads where you are having to do this every few minutes became very annoying. I could have stayed under 20 but that would have put us into camp very late and I was traveling with some else so I did not want to slow them down.

I currently have 195,000 on my rig. Just recently the bushings on the top of the rear shocks have gone bad. I am opting to switch out for a traditional suspension. If it wasn't for that I would use the AHC until it went out. Just keep in mind you have it in park to raise or lower the Lexus. You cannot do this as you drive.

 

[Clunky]

Last year I went on a trip where we traveled from New Mexico to Colorado on primarily Forest service roads. I did this with AHC as mine was in great condition. My pressures and graduations were where they needed to be. We loaded up for the 10 day trip and the AHC leveled itself and handled the weight of the load very well. We even went on some very rough roads that had completely washed out. My problem with the AHC is that in order to put it in High you have to put it in park and wait until it has risen into high. This became very tedious because any time you reached that 20 MPH it would lower. I then would have to rinse and repeat. On roads where you are having to do this every few minutes became very annoying. I could have stayed under 20 but that would have put us into camp very late and I was traveling with some else so I did not want to slow them down.

I currently have 195,000 on my rig. Just recently the bushings on the top of the rear shocks have gone bad. I am opting to switch out for a traditional suspension. If it wasn't for that I would use the AHC until it went out. Just keep in mind you have it in park to raise or lower the Lexus. You cannot do this as you drive.

If you are on forest service roads that allow you to cruise along at over 20 MPH, why bother with high mode? The clearance in normal mode is still pretty good.

 

[Stevehats]

There where certain stretches where very little maintenance had been done. So there where large rivets and dips that I did not want to take the chances of hitting the bumper as I run stock in both front and rear as of now. And the hitch on the back is integrated into the bumper. So I didn't have the hitch to "protect" the rear bumper. I also have not done any wheeling or Overlanding until this year. So I am probably more careful than most. Got my 470 December of 2018.

 

[nothappening]

Last year I went on a trip where we traveled from New Mexico to Colorado on primarily Forest service roads. I did this with AHC as mine was in great condition. My pressures and graduations were where they needed to be. We loaded up for the 10 day trip and the AHC leveled itself and handled the weight of the load very well. We even went on some very rough roads that had completely washed out. My problem with the AHC is that in order to put it in High you have to put it in park and wait until it has risen into high. This became very tedious because any time you reached that 20 MPH it would lower. I then would have to rinse and repeat. On roads where you are having to do this every few minutes became very annoying. I could have stayed under 20 but that would have put us into camp very late and I was traveling with some else so I did not want to slow them down.

I currently have 195,000 on my rig. Just recently the bushings on the top of the rear shocks have gone bad. I am opting to switch out for a traditional suspension. If it wasn't for that I would use the AHC until it went out. Just keep in mind you have it in park to raise or lower the Lexus. You cannot do this as you drive.

Is this a Lexus only feature of the AHC? I find that very strange. I haven't needed to put my LC in park the change heights.

Edit: in fact my routine when I'm parking is to press "Low" as I'm approaching the parking spot and by the time I'm finished the truck is already in Low long before I've put it into park.

 

[BEG]

There where certain stretches where very little maintenance had been done. So there where large rivets and dips that I did not want to take the chances of hitting the bumper as I run stock in both front and rear as of now. And the hitch on the back is integrated into the bumper. So I didn't have the hitch to "protect" the rear bumper. I also have not done any wheeling or Overlanding until this year. So I am probably more careful than most. Got my 470 December of 2018.

I run 90% of the time in "N" when off-road, only switching to "H" when crawling. If you're able to move fast enough to drop back to "N" you probably don't need to be in "H."

Couple extra benefits of AHC when off-road:
- The "H" height is actual lifted height, not unloaded height like conventional. AHC will lift you up to the same height and keep you there regardless of load (assuming you don't max it out).
- "L" is very handy for ducking under obstacles while on the trail
- Extra-high mode. Gives you an extra 1" of lift when it senses wheel spin in 4L.