LX570 AHC height modifications (lift it!) (5 Viewers)

[Heckraiser]

Yes, I avoided H like the plague with my old E-rated nittos due to stiff bouncy ride off road. Now that I've got D-rated Mickey Thompsons in a wide enough size that I'm comfortable airing down much lower, I do use H more, but N is definitely best for comfort.

Do you really think worn springs would account for a 1" difference between sides? Seems odd they wouldn't be equally worn. FWIW, I did break my front driver AHC sensor being a goon, and replaced with a used one, but I had the exact same "lean" before and after with the new sensor adjusted all the way to lift.

 

[TeCKis300]

Yes, I avoided H like the plague with my old E-rated nittos due to stiff bouncy ride off road. Now that I've got D-rated Mickey Thompsons in a wide enough size that I'm comfortable airing down much lower, I do use H more, but N is definitely best for comfort.

Do you really think worn springs would account for a 1" difference between sides? Seems odd they wouldn't be equally worn. FWIW, I did break my front driver AHC sensor being a goon, and replaced with a used one, but I had the exact same "lean" before and after with the new sensor adjusted all the way to lift.

I see. Sounds like your globes are worn/bottoming out and just new globes will make a huge difference. Since you also sensor lifted without spacers in, that also puts more load on the globes making them more likely to cause this symptom. I give @grinchy credit for encouraging me to swap them even as I didn't have any harsh symptoms. AHC high can be just as plush as normal position when the globes are healthy. Then with AHC long travel, even a sensor lift will still have great plush slinky travel and articulation. Not that I need them but I've run LT-Es exclusively through 3 tires now, 33s, 35s, and 37s (because that's what's available in the sizes I like to run). When aired down, it's a magic carpet ride. Able to hold huge speed (damper in Sport) alongside Raptors that like to run.

Yes, worn springs that have taken a set to one side are a normal symptom since the beginnings of 4x4s. Look at any 4x4 forum and you'll see lots of the same questions. Trim packers exist to address this very problem. Or you can just get new springs as they're not terribly expensive.

 

[rherrco]

I see. Sounds like your globes are worn/bottoming out and just new globes will make a huge difference. Since you also sensor lifted without spacers in, that also puts more load on the globes making them more likely to cause this symptom. I give @grinchy credit for encouraging me to swap them even as I didn't have any harsh symptoms. AHC high can be just as plush as normal position when the globes are healthy. Then with AHC long travel, even a sensor lift will still have great plush slinky travel and articulation. Not that I need them but I've run LT-Es exclusively through 3 tires now, 33s, 35s, and 37s (because that's what's available in the sizes I like to run). When aired down, it's a magic carpet ride. Able to hold huge speed (damper in Sport) alongside Raptors that like to run.

Yes, worn springs that have taken a set to one side are a normal symptom since the beginnings of 4x4s. Look at any 4x4 forum and you'll see lots of the same questions. Trim packers exist to address this very problem. Or you can just get new springs as they're not terribly expensive.

I am not sure what you mean by “worn springs”, but springs don’t wear out. Springs may get shorter if their tensile strength is exceeded by a certain percent but typically a compression spring is designed so it can compress to its solid height and either not take a set, or if it does, it only sets the first time or two it is compressed. That means it is not going to get shorter through high cycle life. (Think engine valve springs) It may break due to a minor surface defect working its way through the wire, kind of like a chip in your windshield propagates.
All that means is your leaning problem is most likely due to the ahc. I know a lot about mechanical springs, but I’ll be damned if I can figure out hydraulics. My ride comfort selector does nothing noticeable even after I replaced the globes, so process of elimination leads me to think the pressure valving in the shocks isn’t working. Anyone know how to check it?

 

[TeCKis300]

I am not sure what you mean by “worn springs”, but springs don’t wear out. Springs may get shorter if their tensile strength is exceeded by a certain percent but typically a compression spring is designed so it can compress to its solid height and either not take a set, or if it does, it only sets the first time or two it is compressed. That means it is not going to get shorter through high cycle life. (Think engine valve springs) It may break due to a minor surface defect working its way through the wire, kind of like a chip in your windshield propagates.
All that means is your leaning problem is most likely due to the ahc. I know a lot about mechanical springs, but I’ll be damned if I can figure out hydraulics. My ride comfort selector does nothing noticeable even after I replaced the globes, so process of elimination leads me to think the pressure valving in the shocks isn’t working. Anyone know how to check it?

I agree in general but spring wear, also known as technical spring relaxation is a real thing over long periods of time and cycles. It's likely not huge but just enough that it creates relatively more deflection on some springs than others. The vehicle is generally not perfectly loaded and we know the springs in the rear are asymmetric as they have different part numbers. Combine that with drive shaft torque loads and systemic leans, it shouldn't be a surprise.

It's not AHC. Nor KDSS. I mean it can be if those systems are in disrepair, but the common root cause is springs in a relatively long travel vehicle taking a set.

 

[rherrco]

I agree in general but spring wear, also known as technical spring relaxation is a real thing over long periods of time and cycles. It's likely not huge but just enough that it creates relatively more deflection on some springs than others. The vehicle is generally not perfectly loaded and we know the springs in the rear are asymmetric as they have different part numbers. Combine that with drive shaft torque loads and systemic leans, it shouldn't be a surprise.

It's not AHC. Nor KDSS. I mean it can be if those systems are in disrepair, but the common root cause is springs in a relatively long travel vehicle taking a set.

I ran a spring manufacturing company for 30 years, so trust me when I tell you automotive suspension springs (at least OEM or reputable companies like Eibach) are designed so relaxation is not an issue. I%? Maybe. It all depends on the percent of tensile strength the spring is designed to be subjected to, usually around 33% max. A suspension spring in a car at rest is not going to noticeably relax, unlike a spring maker who retires after thirty odd years in the business. The bigger concern is the spring taking a set from being compressed beyond its design limits. If the spring has been over stressed and is now 1inch shorter, it will still have the same rate as it had originally.
But, can any one tell me what actually happens in the suspension system when one moves the ride setting from comfort to sport?

 

[TeCKis300]

I ran a spring manufacturing company for 30 years, so trust me when I tell you automotive suspension springs (at least OEM or reputable companies like Eibach) are designed so relaxation is not an issue. I%? Maybe. It all depends on the percent of tensile strength the spring is designed to be subjected to, usually around 33% max. A suspension spring in a car at rest is not going to noticeably relax, unlike a spring maker who retires after thirty odd years in the business. The bigger concern is the spring taking a set from being compressed beyond its design limits. If the spring has been over stressed and is now 1inch shorter, it will still have the same rate as it had originally.
But, can any one tell me what actually happens in the suspension system when one moves the ride setting from comfort to sport?

Nice. It's always great to hear firsthand knowledge and I'm sure you have more experience here. Agreed designs are not going to have the spring work into plastic deformation. Still, there's some deflection that's going to create some lean over time. Lookup any jeep forum, 80-series, or 4x4. It's a reality so something is at work here. It could just as easily be stackup of deflection and uneven loads as surfaces are never flat, gas tanks aren't centered, bushings and springs are all at play. I personally haven't replaced springs on account of lean so you may be right. However it is explained, trim packers are a good answer.

Regarding damper modes, it's going to be most obvious when the suspension is at work. Meaning broken or roads with lots of sharp transitions. Or sharper turns or cornering. If the vehicle is loaded, it's also more obvious with increased body control. Going straight ahead on a flat surface won't show much difference because the damper system is active. Meaning it'll relax the dampers when less damping force is needed. In sport, it'll be much more aggressive in ramping up damping force.

There's a great thread and dashboard where AHC functions can be viewed in real time.

While staring at the dashboard on my computer monitor i realized how i could make the height control valve monitors more eye appealing... I didn't like just floating a box above the labels for the corner height sensors. It finally occurred to me to use the valve monitor as the label and remove it from the height sensor display. I updated the new dashboard and replaced the link above.

AHC Dashboard v2

 

[rherrco]

Nice. It's always great to hear firsthand knowledge and I'm sure you have more experience here. Agreed designs are not going to have the spring work into plastic deformation. Still, there's some deflection that's going to create some lean over time. Lookup any jeep forum, 80-series, or 4x4. It's a reality so something is at work here. It could just as easily be stackup of deflection and uneven loads as surfaces are never flat, gas tanks aren't centered, bushings and springs are all at play. I personally haven't replaced springs on account of lean so you may be right. However it is explained, trim packers are a good answer.

Regarding damper modes, it's going to be most obvious when the suspension is at work. Meaning broken or roads with lots of sharp transitions. Or sharper turns or cornering. If the vehicle is loaded, it's also more obvious with increased body control. Going straight ahead on a flat surface won't show much difference because the damper system is active. Meaning it'll relax the dampers when less damping force is needed. In sport, it'll be much more aggressive in ramping up damping force.

There's a great thread and dashboard where AHC functions can be viewed in real time.

I am happy to donate whatever info I can remember re mechanical springs. This forum has provided a dangerous amount of insight into my LX and every time I learn something new, I want to go out and try to fix something that may not even be broken. Thanks to whoever posted the article explaining how the ahc-avs system works, I understand how what you are saying works; it’s a lot more complicated than I thought. With respect to the dampening system, my problem is that for any given road surface I go over, it feels the same whether the ride selector is in comfort or sport. Given that all the other myriad ahc and avs functions seem to work as expected, I am suspecting there is a disconnect between the switch and the suspension ECU. Is it time to find someone with a Techstream setup? Thanks for your help.

 

[grinchy]

I am happy to donate whatever info I can remember re mechanical springs. This forum has provided a dangerous amount of insight into my LX and every time I learn something new, I want to go out and try to fix something that may not even be broken. Thanks to whoever posted the article explaining how the ahc-avs system works, I understand how what you are saying works; it’s a lot more complicated than I thought. With respect to the dampening system, my problem is that for any given road surface I go over, it feels the same whether the ride selector is in comfort or sport. Given that all the other myriad ahc and avs functions seem to work as expected, I am suspecting there is a disconnect between the switch and the suspension ECU. Is it time to find someone with a Techstream setup? Thanks for your help.

That’s a sign that the accumulators/globes aren’t doing what they should. They are wear items and have about a 10 year life.

 

[rherrco]

That’s a sign that the accumulators/globes aren’t doing what they should. They are wear items and have about a 10 year life.

They are a week old….
The thing is, everything else about the ahc seems to work fine with the new globes. It’s just the ride selector switch does nothing noticeable.

 

[grinchy]

They are a week old….
The thing is, everything else about the ahc seems to work fine with the new globes. It’s just the ride selector switch does nothing noticeable.

Might consider a rebleed then.

 

[TLCLVR]

I'm finally getting around to sensor lifting my rig and started to go through this thread (again). It strikes me that so much has been learned over the last 7 years it would be helpful to gather the most relevant info and pin it to the start of the thread and put this in the Modifications FAQ. Even better a two section piece with AHC lift and AHC long travel combined?

Maybe it's already been done? If so I can't find it and not looking forward to sifting through 31 pages and 7 years of posts...

 

[lx200inAR]

I'm finally getting around to sensor lifting my rig and started to go through this thread (again). It strikes me that so much has been learned over the last 7 years it would be helpful to gather the most relevant info and pin it to the start of the thread and put this in the Modifications FAQ. Even better a two section piece with AHC lift and AHC long travel combined?

Maybe it's already been done? If so I can't find it and not looking forward to sifting through 31 pages and 7 years of posts...

It would be nice if there could be a wiki type section of the forum. I’m not sure how moderating it would work, but there are many threads that it would be nice to have that way. I suppose one idea could to have a system of upvoting certain posts to “wiki” value and then being able to filter on only those posts.

 

[mceagle555]

Followed @tbisaacs guide early on in the thread to level the front. (Did not adjust rear.) Super easy with a 10mm box wrench and 10mm socket/ratchet.

Measurements below are on level ground from floor to top of wheel well with 275/70/18 (33.2”) tires and 1/2 tank of gas.

Neutral before-after

Front Driver: 35 1/4” >> 35 1/2” (Gain 1/4”)
Front Passenger: 35 1/2” >> 36” (Gain 1/2”)
Rear Passenger: 36 5/8” >> 36 5/8”
Rear Driver: 36 3/8” >> 36 3/8”

High after

Front Driver: 38 1/8”
Front Passenger: 38 1/2”
Rear Passenger: 39 1/4”
Rear Driver: 38 7/8”

 

[webbdustin]

I'm toying around with mine a bit. Actually relocating the connection rod up 1in tapped into my billet uca. I used a 1/4 in hiem hoint. Essentially by lifting connection point (or with stock arms simply adjust the hiem that much shorter than stock connection rod) you move the range of motion in the AHC. Thus ride hight can be moved above allowable parameters. Of course at this point uca and diff drop should be necessities. Down side of this is that ride hight is now that much closer to full droop (what we call pogoing). The solution is moving the shock mounts up and or add strut spacers. This moves the shocks range of motion to be centered with ride hight which in turn corrects excessive AHC pressure. Now to do the same in the rear!!!!

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Can you provide more information regarding the modification of the billet upper control arm to utilize the AHC. I'm looking to replace stock UCA with billet and maintain AHC. It looks like you already did this?