AHC and Non AHC Torsion Bars Question

[05JLX470]

Hi guys and please forgive me if this has been answered. I did some searching and came up with conflicting answers. I am a recent owner of a 05 LX. I did a AHC sensor lift in the front of about 1" just to get rid of some of the rake. I also cranked the torsion bars about 15 turns to get the AHC pressures in spec. I understand the LX torsion bar is lighter weight and smaller dia than a non AHC LC stock bar. Instead of cranking the stock worn out bar 15 turns, what about installing a new stock (OEM) set of LC TB's, to carry the load. I am going to be installing a winch bumper and air comp up front at some stage. Would the OEM LC bars work OK with the AHC LX with my slight sensor lift and heavier equipment up front, or are they to heavy of a bar with the hyd shocks ? Like I said after doing a search, seems like there are conflicting opinions. Please chime in Paddo !!!

Thanks in advance for any help...........

 

[TXLX100]

It's been covered before, you may have to search for a while but there are threads. If I recall, if you will have significant weight, it's a viable option to use stock T-bars with AHC. You may find some info for upgraded rear coils you can use with AHC as well (or air bag it)

 

[BEG]

I've had his conversation with @PADDO but I'm sure he'll chime in. You can use the non-AHC t-bars, but they are a significant increase in spring rate. I believe the AHC bars are 25mm in diameter and the non-AHC are 28mm. The only way to know for sure is to try it. If you can get your AHC pressures in the front high enough to keep the fluid flowing (maybe around 6.3?) with the non-AHC bars, the system has enough adjustability to work. That being said, I don't think the system is designed to work with the front end so far out of height spec compared to the rear. Most people doing a sensor lift raise the front and rear equally.

It would help you, I think, to mentally separate the action of cranking the t-bars (increasing preload) to that of changing t-bars (increasing rate). Both will raise the height of the load (when AHC is not active) but the latter will drastically change the way the suspension behaves. See what you can do with the AHC bars first, even if that means re-indexing them. I have a steel winch bumper, winch and often have a hi-lift mounted to the bull bar, and the AHC bars are still good.

 

[codertimt]

I'll also chime in echo @BEG's thoughts...I have a Dissent front bumper with full bar and winch and am still on the stock torsion bars. I am pretty much at stock height though, but have adjusted bars so that pressures are actually on the low side to match my rear pressures which are on the the low side even with rear drawer, 4x4 labs rear bumper/tire carrier/jerry cans/etc because I'm running 80 series rear springs. My front bumper is one of the lighter ones and my rear bumper is definitely heavy, so it works pretty well for me... Feels pretty good for the most part, and since I can't recall seeing anyone posts pressures after installing non-AHC bars, I'll stick with it until I have an issue...

 

[neilsen100]

I don't yet have experience with the t-bar swap but I have changed out the rear springs from the AHC model to the stock LC model. I consistently have a RTT, drawers, fridge, rear bumper and camping stuff in my LX. Estimated weight is more than 400 extra pounds.

My pressures with stock AHC springs was 9.8. After replacing with LC non-AHC springs my rear pressures dropped to 5.2. I think changing your Tbars might be too much but adjusting or reindexing is the best bet.

 

[sonk76]

Been running non-AHC rear coils, and non-AHC OEM t-bars for years now, with AHC raised.

It improved ride quality and seemed to help cope with added weight from "expo" junk

 

[BEG]

Been running non-AHC rear coils, and non-AHC OEM t-bars for years now, with AHC raised.

It improved ride quality and seemed to help cope with added weight from "expo" junk

What are your front and rear pressures and how high is it raised?

 

[05JLX470]

What are your front and rear pressures and how high is it raised?

Thanks for all the responses guys. The more the input the better. I too would like the see the sonk76 response. Thanks for the question BEG !

 

[sonk76]

Never measured; if someone has a techstream in 19002 happy to have it measured (or a link to where to get one cheaply.)

 

[BEG]

Never measured; if someone has a techstream in 19002 happy to have it measured (or a link to where to get one cheaply.)

Happy to help you out if you're ever in Camden, Mon-Fri. Techstream was too fiddly for me. I went with the iCarsoft TYTII scanner.

 

[thetoyotaman]

Curious if the iCarsoft TYTII scanner can also program TPMS.

 

[sonk76]

What are your front and rear pressures and how high is it raised?

With my recent techstream access, the specs are now:

Front: 6.9
Rear: 4.7
Accumulator: 10.6

 

[BEG]

Rear pressure is way low. Throw some sandbags in it! But seriously, I'm surprised the front is as high as it is with LC bars. What do have up there?

 

[sonk76]

Rear pressure is way low. Throw some sandbags in it! But seriously, I'm surprised the front is as high as it is with LC bars. What do have up there?

I'm very happy with it as it is. The suspension works wonderfully well, and I have capacity to load up the truck with lots of gear as needed, while still raising suspension to High as needed.

The front is tuned to be exactly at factory spec to my knowledge, so not sure what you mean by it being high. (you can pretty much adjust the front to what ever you want, regardless of what torsion bars you are running...). that said, that is only a static pressure number at a fixed height, in practice the stiffness of the torsion bar will have big impact on the pressures as you start moving from that static height...

 

[BEG]

I'm very happy with it as it is. The suspension works wonderfully well, and I have capacity to load up the truck with lots of gear as needed, while still raising suspension to High as needed.

The front is tuned to be exactly at factory spec to my knowledge, so not sure what you mean by it being high. (you can pretty much adjust the front to what ever you want, regardless of what torsion bars you are running...). that said, that is only a static pressure number at a fixed height, in practice the stiffness of the torsion bar will have big impact on the pressures as you start moving from that static height...

I know the front pressure is to spec for factory AHC bars, but the LC bars have a significantly higher spring rate. So they're "high" relative to what they should be, assuming everything else is the same. That's why I asked. The rears are what I expected.

 

[sonk76]

I know the front pressure is to spec for factory AHC bars, but the LC bars have a significantly higher spring rate. So they're "high" relative to what they should be, assuming everything else is the same. That's why I asked. The rears are what I expected.

I'm still not quite sure if I'm tracking with you in terms of the "'high' relative to what they should be." The higher spring rate is relevant in that it allows the system to be better handle the extra mass that is up there (from armor, skids, winch, etc.), and I've never heard of an "alternate" target AHC pressure that should be dialed in when using different stiffness Torsion Bars.

If your point is that had I simply swapped torsion bars and not adjusted anything else, on an otherwise "stock" vehicle, then the front pressure would likely be lower on the AHC (before adjusting torsion bars) then I agree--but that's not my situation.

I guess I'm just picking up on your word "should". Everyone is welcome to run theirs pressures as they wish. I choose to run mine at the factory spec (regardless of my Torsion Bar choice). This setup, combined with brand new OME globes, has made the vehicle run incredibly smoothly.

I'm not an expert on this, so just speaking from my own real-world experience--others who know much more than I, like @PADDO can probably better advise on the theoretical optimals.

YMMV!

 

[BEG]

I'm still not quite sure if I'm tracking with you in terms of the "'high' relative to what they should be." The higher spring rate is relevant in that it allows the system to be better handle the extra mass that is up there (from armor, skids, winch, etc.), and I've never heard of an "alternate" target AHC pressure that should be dialed in when using different stiffness Torsion Bars.

If your point is that had I simply swapped torsion bars and not adjusted anything else, on an otherwise "stock" vehicle, then the front pressure would likely be lower on the AHC (before adjusting torsion bars) then I agree--but that's not my situation.

I guess I'm just picking up on your word "should". Everyone is welcome to run theirs pressures as they wish. I choose to run mine at the factory spec (regardless of my Torsion Bar choice). This setup, combined with brand new OME globes, has made the vehicle run incredibly smoothly.

I'm not an expert on this, so just speaking from my own real-world experience--others who know much more than I, like @PADDO can probably better advise on the theoretical optimals.

YMMV!

Sorry if I'm not explaining myself. The higher spring rate torsion bars will naturally carry a higher percentage of weight than the originals at any given height. So, in order for the system neutral pressure at the front to be 6.9, something in the suspension would have to be adjusted to compensate. Either a sensor lift, extra weight, etc. That's what I was asking about. I run my pressures at 6.7 and 5.6, front and rear, respectively, on OEM front t-bars and King rears, so it's surprising to me that you could achieve 6.9MPa even with little to no preload on the LC bars which were sized to take the full load of the vehicle.

 

[thetoyotaman]

I'm very happy with it as it is. The suspension works wonderfully well, and I have capacity to load up the truck with lots of gear as needed, while still raising suspension to High as needed.

The front is tuned to be exactly at factory spec to my knowledge, so not sure what you mean by it being high. (you can pretty much adjust the front to what ever you want, regardless of what torsion bars you are running...). that said, that is only a static pressure number at a fixed height, in practice the stiffness of the torsion bar will have big impact on the pressures as you start moving from that static height...

Curious your comparisons between stock and lx torsion bars on the front end in regards to driveability.

 

[sonk76]

Curious your comparisons between stock and lx torsion bars on the front end in regards to driveability.

In my case, there was a big improvement in ride quality. I think the original springs struggled with the extra weight (made more challenging by the AHC lift).

EDIT: I do have a lot of extra weight up front, with bumper, sliders, Group 31 battery, winch with steel cable, under frame armor, etc...