AHC: what are the pros/cons?

[BEG]

A big issue, IMO, is the unwillingness of the aftermarket to put any effort into upgrades for the AHC crowd. The system is incredibly robust, but is still limited by the weight range within which it's designed to operate. That's really the only benefit of aftermarket suspensions over AHC. Personally, I'd love to see:

- AHC upgraded torsion bars. T-bars are great for ease of continuous and (virtually) unlimited pre-load adjustment (with the aid of re-indexing when required) but not spring rate. If someone would step up and make a torsion bar with a spring rate somewhere between OEM AHC and OEM non-AHC, that would be the sweet spot for most typical overland setups.

- Adjustable, rebuildable shock actuators. Contrary to the usual shorthand we throw around when it comes to shock actuators ("they're just hydraulic rams") they do actually have some "pre-damping" built in to help take the edge off 16-position dampers on the frame. A set of shock actuators with 3, manually adjustable settings (soft/OEM/sport) would make it easier to match the rate of your chosen springs and basically allow a huge combination of damper settings when factoring in the comfort-sport dial and the computer-controlled settings.

- Rear pre-load adjustment. Could be a as simple as a screw-type spring adjuster or as complex as a rear coil-over conversion, but the ability to independently fine-tune the pre-load at the rear for perfect neutral pressure at any weight would go a long way in balancing the ride and keeping your AHC happy and healthy for a long time.

 

[Stevehats]

A big issue, IMO, is the unwillingness of the aftermarket to put any effort into upgrades for the AHC crowd. The system is incredibly robust, but is still limited by the weight range within which it's designed to operate. That's really the only benefit of aftermarket suspensions over AHC. Personally, I'd love to see:

- AHC upgraded torsion bars. T-bars are great for ease of continuous and (virtually) unlimited pre-load adjustment (with the aid of re-indexing when required) but not spring rate. If someone would step up and make a torsion bar with a spring rate somewhere between OEM AHC and OEM non-AHC, that would be the sweet spot for most typical overland setups.

- Adjustable, rebuildable shock actuators. Contrary to the usual shorthand we throw around when it comes to shock actuators ("they're just hydraulic rams") they do actually have some "pre-damping" built in to help take the edge off 16-position dampers on the frame. A set of shock actuators with 3, manually adjustable settings (soft/OEM/sport) would make it easier to match the rate of your chosen springs and basically allow a huge combination of damper settings when factoring in the comfort-sport dial and the computer-controlled settings.

- Rear pre-load adjustment. Could be a as simple as a screw-type spring adjuster or as complex as a rear coil-over conversion, but the ability to independently fine-tune the pre-load at the rear for perfect neutral pressure at any weight would go a long way in balancing the ride and keeping your AHC happy and healthy for a long time.

That is my problem is I am going to start adding weight. And it sucks that you have to speculate and try something that may not even work. But with a traditional suspension system it is much easier to tell what will work with what you are putting on the vehicle. To be honest I am torn. I will have made up my mind only to change it a couple hours later.

 

[J1000]

- Rear pre-load adjustment. Could be a as simple as a screw-type spring adjuster or as complex as a rear coil-over conversion, but the ability to independently fine-tune the pre-load at the rear for perfect neutral pressure at any weight would go a long way in balancing the ride and keeping your AHC happy and healthy for a long time.

That is a cool wish list, but just to point out that rear air bags can achieve this goal pretty easily.

 

[BEG]

That is my problem is I am going to start adding weight. And it sucks that you have to speculate and try something that may not even work. But with a traditional suspension system it is much easier to tell what will work with what you are putting on the vehicle. To be honest I am torn. I will have made up my mind only to change it a couple hours later.

It's actually pretty straight forward with AHC. There is a published payload within which you can remain stock. Once you exceed it, you have to make adjustments to keep it happy. It's pretty easy to tell if the system is happy by checking the neutral pressure. Once you're outside the range, you have to upgrade springs, add higher pressure globes etc. If you REALLY load it up (full steel armor, RTT, towing a trailer, family of five 250# adults, dual battery, 5 jerry cans of water, etc.) you may end up operating beyond the capability of the dampers, but honestly at that point you're well beyond the vehicles GVWR anyway.

My post was about improving the performance even more. There's a perception that anything aftermarket is better than OEM ("I replaced my AHC with a $700 OME kit and it rides SO AWESOME!") and that's hard to shake people out of. I'd like to see some REAL performance parts made for AHC.

 

[BEG]

That is a cool wish list, but just to point out that rear air bags can achieve this goal pretty easily.

No, they can't. Not without increasing the spring rate.

 

[Stevehats]

But lexus doesn't make higher pressure globes correct? You would have to go after market and I have heared mixed reviews with those.

 

[suprarx7nut]

No, they can't. Not without increasing the spring rate.

I wonder how many folks could really feel that difference though, in an armored 100. If you compared AHC setups with proper pressures and a variety of springs I bet the typical enthusiast would only feel the unmatched spring rate when you're way off.

 

[suprarx7nut]

But lexus doesn't make higher pressure globes correct? You would have to go after market and I have heared mixed reviews with those.

No, no, no.

Globes are always the same pressure.

You can change the pressure the AHC system needs to provide to reach the target ride height. You chagne that by making the steel springs do more or less work. That is done via front torsion adjustment (free, just grab a wrench) or by changing out the rear springs, spacers, air bags to achieve the proper rear pressure at neutral.

 

[Stevehats]

No, no, no.

Globes are always the same pressure.

You can change the pressure the AHC system needs to provide to reach the target ride height. You chagne that by making the steel springs do more or less work. That is done via front torsion adjustment (free, just grab a wrench) or by changing out the rear springs, spacers, air bags to achieve the proper rear pressure at neutral.

Are the king springs the only option or could you put on like Dobinsons for example?

 

[BEG]

I wonder how many folks could really feel that difference though, in an armored 100. If you compared AHC setups with proper pressures and a variety of springs I bet the typical enthusiast would only feel the unmatched spring rate when you're way off.

You might be right. I'm wary of combining too many types of springs (coils + nitrogen + air) when trying to hit a specific spring rate. Especially progressive ones. Might be OK in most application, but my post was more geared towards solutions tailored toward the AHC for performance boosts. I would love to be able to corner-weight my rig and then dial in my spring rate and pre-load at every corner with a full load before a long trip.

 

[BEG]

No, no, no.

Globes are always the same pressure.

Not necessarily. The spring rate provided by the globes is dependent on the pressure of the nitrogen charge and the volume of the globe. The higher the gas volume > the more compressible the charge > the lower the resulting spring rate and vice versa. You could put rear globes at all four corners and get a lower spring rate than OEM because the rear globes are higher volume than the front. You could do the opposite using only front globes and get a higher spring rate. Or you can install Citroen globes from Pleiades which are even smaller and get an even higher spring rate. Or you can get Pleiades to fill the globes to a higher PSI and so on and so forth.
Personally, this is not where I would look to increase spring rate, since the progressive nature of compressed gas is a little less straightforward (to my feeble brain) than that of a torsion bar.

 

[BEG]

Are the king springs the only option or could you put on like Dobinsons for example?

The King KTRS-79 are the only ones that are made for the AHC as an upgrade to the stock coils. There are also some OEM options from the 80 series that can be used. The next step up would be the OEM non-AHC coils for EXTREME weight addition. The spring rate of OME, Ironman, Dobinsons and any other aftermarket coil designed for non-AHC applications would be way too high for just about any rig running AHC that wasn't already heavily modified in some other ways to take the weight.

 

[suprarx7nut]

Not necessarily. The spring rate provided by the globes is dependent on the pressure of the nitrogen charge and the volume of the globe. The higher the gas volume > the more compressible the charge > the lower the resulting spring rate and vice versa. You could put rear globes at all four corners and get a lower spring rate than OEM because the rear globes are higher volume than the front. You could do the opposite using only front globes and get a higher spring rate. Or you can install Citroen globes from Pleiades which are even smaller and get an even higher spring rate. Or you can get Pleiades to fill the globes to a higher PSI and so on and so forth.
Personally, this is not where I would look to increase spring rate, since the progressive nature of compressed gas is a little less straightforward (to my feeble brain) than that of a torsion bar.

Fair enough, but I guess my point is that for the folks asking what parts to use for AHC, just trying to keep the system running, you can assume the globes are a fixed variable. They are what they are and you tune other items in the system to keep up with your mods.

I'm sure you *could* modify pressures in the globes by swapping parts and modify handling characteristics, but that's beyond what's needed to ensure your AHC works reliably.

 

[BEG]

Fair enough, but I guess my point is that for the folks asking what parts to use for AHC, just trying to keep the system running, you can assume the globes are a fixed variable. They are what they are and you tune other items in the system to keep up with your mods.

I'm sure you *could* modify pressures in the globes by swapping parts and modify handling characteristics, but that's beyond what's needed to ensure your AHC works reliably.

Agreed. You don't need to mess with them.

 

[99toylc]

Nvm

 

[J1000]

Damn this thread has all of the info condensed into only 3 pages. I learned a lot. I'm definitely going to be keeping my AHC running as long as possible. I just had it on my driveway in L for the guy replacing my windshield and then raised it to H to work on some wiring behind the bumper and just loved watching it raise up from lowrider to modified 4x4 in seconds.

 

[suprarx7nut]

Damn this thread has all of the info condensed into only 3 pages. I learned a lot. I'm definitely going to be keeping my AHC running as long as possible. I just had it on my driveway in L for the guy replacing my windshield and then raised it to H to work on some wiring behind the bumper and just loved watching it raise up from lowrider to modified 4x4 in seconds.

On my LX at this moment, I'm taking out the intake manifold in my garage. It's a world of difference working deep int he engine bay with it in L compared to N or compared to my slightly lifted 99 on big tires.

The benefits go on and on...

 

[Stevehats]

On my LX at this moment, I'm taking out the intake manifold in my garage. It's a world of difference working deep int he engine bay with it in L compared to N or compared to my slightly lifted 99 on big tires.

The benefits go on and on...

Sitting here wishing I would have put it in low to do the timing belt. I always put it in high to change the oil .

 

[Sargy]

Are the king springs the only option or could you put on like Dobinsons for example?

I have Dobinson standard height 80 series springs. No spring ratesn but from a distant forum page I read up on they are rated slightly differently from the 80 series. Various reviews show that it's a more comfort oriented spring and I believe is progressive rated. I think the stock 80 series has a fixed rate for the rear springs

*AHC begins to work properly once 300lbs is added to the rear. A dissent steel rear bumper and spare tire fixes that. A temporary solution is to run x4 70lb bags of sand from lowes and have a full tank of gas.*

On my LX at this moment, I'm taking out the intake manifold in my garage. It's a world of difference working deep int he engine bay with it in L compared to N or compared to my slightly lifted 99 on big tires.

The benefits go on and on...

Sitting here wishing I would have put it in low to do the timing belt. I always put it in high to change the oil .

You could always bleed the front accumulator and watch it drop even lower. Then perform your tasks and refill with fresh AHC fluid

Great thread.

 

[JMK4]

This thread has a lot of useful info! I’ve thought about replacing my AHC, but I’m going to keep it. I’ll be doing a flush as soon as the AHC fluid gets here. What’s the easiest way to read the pressures? I thought I had seen someone use a reader of some kind that was handheld, which I would prefer a portable solution if possible over my laptop.

Also, can anyone tell me what the height difference from low to high, and low to extra high is?