Question about lifting/X-Reas oil amount

[kylebacc]

Hey all,

Just looking for some input on a question I have. It's not for any particular purpose, so no problem solving here. When you lift an X-Reas equipped truck, and keep the system (just change to taller coils or add spacers), if hydraulic fluid does not expand or compress, are the shocks under a "negative" pressure all the time since they are all pulled an extra couple/few inches out? What do you guys think?

 

[CJ3Flyr]

Hey all,

Just looking for some input on a question I have. It's not for any particular purpose, so no problem solving here. When you lift an XREAS equipped truck, and keep the system (just change to taller coils or add spacers), if hydraulic fluid does not expand or compress, are the shocks under a "negative" pressure all the time since they are all pulled an extra couple/few inches out? What do you guys think?

Hmmmm... Good point, maybe a little. There's so little XREAS service info available that it's really hard to know how much oil should be added. IMHO, you're right, some small amount of XREAS fluid should be added when a vehicle is 4-corner lifted. The lack of info about the system is amazing to me. Even the FSM basically just comes with R&R instructions. I'm sure there's some Tokiko .PDF somewhere that covers how to fill it.

It seems to me that you would want the lines bled and full. The question is when? When it's on the ground supporting the vehicle weight or when it's in the air? If it's in the air then it's probably fine as-is with a small lift. In a perfect world you'd be able to adjust the precharge in the accumulator.

 

[Jed]

I don't think so. The XREAS suspension is obviously designed to expand and contract with the oil level remaining constant. Lifting an XREAS vehicle will only alter the "resting" position of the pistons in the accumulators and should not require any additional oil. In fact, adding oil would most like overcharge the system and could even cause leaks.

 

[CJ3Flyr]

I don't think so. The XREAS suspension is obviously designed to expand and contract with the oil level remaining constant. Lifting an XREAS vehicle will only alter the "resting" position of the pistons in the accumulators and should not require any additional oil. In fact, adding oil would most like overcharge the system and could even cause leaks.

Yes but wouldn't the fact all 4 shocks are extended further at rest warrant a few more ounces of oil? That's how I'm looking at it.

 

[kylebacc]

Hmmmm... Good point, maybe a little. There's so little XREAS service info available that it's really hard to know how much oil should be added. IMHO, you're right, some small amount of XREAS fluid should be added when a vehicle is 4-corner lifted. The lack of info about the system is amazing to me. Even the FSM basically just comes with R&R instructions. I'm sure there's some Tokiko .PDF somewhere that covers how to fill it.

It seems to me that you would want the lines bled and full. The question is when? When it's on the ground supporting the vehicle weight or when it's in the air? If it's in the air then it's probably fine as-is with a small lift. In a perfect world you'd be able to adjust the precharge in the accumulator.

Yes the lack of information is annoying. I would imagine it wouldn't make a difference whether it was in the air or on the ground, as long as all of them were the same (on the ground or in the air).

I don't think so. The XREAS suspension is obviously designed to expand and contract with the oil level remaining constant. Lifting an XREAS vehicle will only alter the "resting" position of the pistons in the accumulators and should not require any additional oil. In fact, adding oil would most like overcharge the system and could even cause leaks.

I don't follow. It's made to expand and contract, but not all at the same time. Only when work is being performed on it should all the wheels be expanded at the same time. I don't think it's meant to be expanded that distance, and then driving like that on top of it. I think fluid should be added :/

Yes but wouldn't the fact all 4 shocks are extended further at rest warrant a few more ounces of oil? That's how I'm looking at it.

X2 as stated above. Also, to go along with this discussion:

The X-Reas system is made to actively equalize the two shocks that are connected right? Well, what about lifting 3" in front and only 2" in the back? Wouldn't that make the system want to always try and push fluid to the back shocks? Because it thinks they are compressed more than the fronts?

 

[CJ3Flyr]

Well, what about lifting 3" in front and only 2" in the back? Wouldn't that make the system want to always try and push fluid to the back shocks? Because it thinks they are compressed more than the fronts?

IMHO it's tricky... How was the front lifted? If it's just top spacer then the shock extension (at rest) is the same as stock. The rears would be extended. For the fronts to deviate from OE you almost have to change springs or have some pre-load included in your spacer setup.

 

[kylebacc]

Ya I see what you mean about a topout spacer. what about a pre-load though? That would extend the front shock, yes? Just a little info about the REAS system when it was originally developed for the supra. It has since evolved into what we have today on our trucks:

Detail | YAMAHA MOTOR

Doesn't really shed any light on our particular subject, but I figured I'd throw it in there anyway

 

[CJ3Flyr]

That would extend the front shock, yes? IMHO, yes, I agree.
Detail | YAMAHA MOTOR Very cool!

:cheers:

 

[Jed]

I don't follow. It's made to expand and contract, but not all at the same time. Only when work is being performed on it should all the wheels be expanded at the same time. I don't think it's meant to be expanded that distance, and then driving like that on top of it. I think fluid should be added :/

Think about driving at speed over a railroad crossing. The front suspension will compress, followed immediately by the rear suspension. Imagine that you're going fast enough to actually get some air (just for the sake of this discussion). The front and rear suspension will go from compressed to extended at all corners. Then when you land, the entire suspension goes from extended to compressed at the same time. Basically the same thing happens when you crest a hill at speed. The suspension is always loading and unloading.

 

[kylebacc]

Think about driving at speed over a railroad crossing. The front suspension will compress, followed immediately by the rear suspension. Imagine that you're going fast enough to actually get some air (just for the sake of this discussion). The front and rear suspension will go from compressed to extended at all corners. Then when you land, the entire suspension goes from extended to compressed at the same time. Basically the same thing happens when you crest a hill at speed. The suspension is always loading and unloading.

Right. I get that. But it's not meant to stay partially "unloaded" all the time, which would essentially be the case when you lift without adding a drop bracket. Do you think this would result in the shocks trying to compress themselves all the time (to an extent)?

 

[Jed]

Right. I get that. But it's not meant to stay partially "unloaded" all the time, which would essentially be the case when you lift without adding a drop bracket. Do you think this would result in the shocks trying to compress themselves all the time (to an extent)?

No, I really don't think so. Shocks don't ever try to compress or extend. Imagine a vehicle with a suspension made up of springs and no shocks. It would bounce all over the place constantly. The shocks are there to dampen this movement.

Ride height is determined by the springs. Think about old, worn out springs that are sagging. Of course the ride height will be affected, but the shocks would still perform as they should, so long as they are within their operating range (between compression and extension). I think XREAS would behave the same way.

 

[kylebacc]

No, I really don't think so. Shocks don't ever try to compress or extend. Imagine a vehicle with a suspension made up of springs and no shocks. It would bounce all over the place constantly. The shocks are there to dampen this movement.

Ride height is determined by the springs. Think about old, worn out springs that are sagging. Of course the ride height will be affected, but the shocks would still perform as they should, so long as they are within their operating range (between compression and extension). I think XREAS would behave the same way.

Shocks don't ever try to compress or extend....unless they are attached to a hydraulic controller that tries to make them to just that...compress and extend as it sees fit. I don't think you can compare what a regular shock would do to an X-REAS shock. Yes they are filled with nitrogen like a regular shock, but then they are also filled with hydraulic fluid in a separate chamber that can be pulled and pushed in and out. We'll probably never know for sure, but I'm enjoying trying to figure it out :bravo:

 

[Jed]

Shocks don't ever try to compress or extend....unless they are attached to a hydraulic controller that tries to make them to just that...compress and extend as it sees fit. I don't think you can compare what a regular shock would do to an X-REAS shock. Yes they are filled with nitrogen like a regular shock, but then they are also filled with hydraulic fluid in a separate chamber that can be pulled and pushed in and out. We'll probably never know for sure, but I'm enjoying trying to figure it out :bravo:

Not sure I'm following you here. Are you saying the XREAS system is some sort of hydraulic controller that is trying to compress or extend the shocks? From my understanding, XREAS is just a diagonally linked system with pistons that act upon hydraulic pressure within each circuit.

What would happen to the XREAS system if, say, we severely overloaded a stationary 4Runner, causing the suspension to rest on its bump stops for an extended period of time? Do you think we'd blow the seals on the XREAS system? Same question for an XREAS equipped 4Runner spending a few days on a chassis lift with all four wheels at full droop. What would happen to the XREAS system?

 

[Jed]

Also keep in mind that XREAS uses hydraulic accumulators, which is the key to this discussion. That's exactly the reason the system has a level of flexibility and most likely should not have the oil level adjusted. Read up on hydraulic accumulators and how they work.

 

[kylebacc]

Not sure I'm following you here. Are you saying the XREAS system is some sort of hydraulic controller that is trying to compress or extend the shocks? From my understanding, XREAS is just a diagonally linked system with pistons that act upon hydraulic pressure within each circuit.

What would happen to the XREAS system if, say, we severely overloaded a stationary 4Runner, causing the suspension to rest on its bump stops for an extended period of time? Do you think we'd blow the seals on the XREAS system? Same question for an XREAS equipped 4Runner spending a few days on a chassis lift with all four wheels at full droop. What would happen to the XREAS system?

I see where you're going with this. I guess you might be right. I also don't know the in's and out's of the X-REAS the way you seem.

Also keep in mind that XREAS uses hydraulic accumulators, which is the key to this discussion. That's exactly the reason the system has a level of flexibility and most likely should not have the oil level adjusted. Read up on hydraulic accumulators and how they work.

I will def do that.

 

[Jed]

Hey, I'm no expert on XREAS. I do know a little bit about hydraulic systems though.... either way, if you find something out in your research, let us know.

 

[kylebacc]

Hey, I'm no expert on XREAS. I do know a little bit about hydraulic systems though.... either way, if you find something out in your research, let us know.

Will do.