Sway Bar Tuning and Musings (2 Viewers)

[TeCKis300]

I’ve been messing with the sway bars on the LX in an attempt to increase front end articulation. Not that it needs it and it’s perfectly slinky. But tweaking is my illness. In this case, taking advantage of added suspension travel provided by AHC Long Travel. Increasing travel creates an opportunity for a larger articulation delta between the front wheels as one side can droop farther while the other side compresses. Adding more compliance to the sway bar can maximize this articulation potential.

With the stock setup, there’s limited ways to increase sway compliance with existing hardware. One possibility that I’ve been exploring is to tweak the chassis brackets and mounts.

Spacing out the front chassis sway bar brackets by ~3/16” with thick washers let’s the sway bushing have more compliance before positively engaging. 3/16” sounds little, but because this is on two chassis points along with the motion ratio and projection of the sway bar, it adds up, and can result in useful additional sway compliance at the wheels.

Initial impressions, yes it works! The front end has more give resulting in a bit softer turn-in on aggressive turns. Yet front end bite is still strong. I know tuning sports cars from my track days, that changing the roll couple and decreasing front end bias can result in more front end traction to actually improve understeer for those willing to push enough. Large amplitude lean (like a freeway on ramp) is still well controlled and generally corners reasonably flat on account of AHCs secondary high spring rate and roll control. Long way to say it still has a good balance with more front end sway compliance. I still need to do more aggressive off-roading, but this should provide more useful articulation. I'll have a chance in a few weeks.

It's a super easy 10 minute install as well. Sway brackets are in the open and easily accessible with IIRC 17mm sockets (M8 bolt). Zip off the bolts, place washers, and zip them back on.

 

[TeCKis300]

Applicability to KDSS​

Sway bar tuning could also benefit KDSS. In similar ways, but perhaps with additional benefits. It’s not spoken about much but there is mounting evidence where KDSS as applied to the 200-series can be a limitation in fast fire roads and baja type running. The 200-series KDSS is a stiff swaybar, with a passive mechanical system which has limits in its ability to decouple. It only unlocks in warp type situations where front and rear axles articulate out of phase. It’s otherwise engaged which takes some of the “independent” out of independent suspension, meaning if one tire hits something, it really affects the other one, and in turn has a greater effect on overall chassis motions. This isn't really a limitation in casual use, but hitting washboards and uneven terrain at over 40-50mph is where this shows.

KDSS has an internal accumulator that accommodates some small bump compliance which is why it's great at lower speeds. Later generations of KDSS, including several flavors of e-KDSS have computer controls to really disengage the sways at low speeds to maximized the ability of each wheel to respond more independently and minimizing transferring forces into the chassis. In later systems, there are kits to allow electronic manual overrides to fully disengage KDSS into higher speeds. It’s been shown that it creates better independent wheel response which has benefits to more comfortable and stable high speed running.

Utilizing the same strategies of shimming the sway bar chassis brackets can open it up to increase compliance for larger bumps and/or faster Baja style running.

 

[TeCKis300]

Reserved...

 

[CanadianRockyCruiser]

This type of spacer is very common on Tundra lifts. I think the same tundra swarybar drop hardware kits may fit.

 

[Boston Mangler]

Ooooh….

Subscribed

 

[turbo8]

Don't you want the spacer to give support to the top of the bushings? It seems like, with just washers, the bushings will flex a lot more and possibly break.

 

[TeCKis300]

This type of spacer is very common on Tundra lifts. I think the same tundra swarybar drop hardware kits may fit.

I might have missed it but what I've seen are drop spacers that move everything down. I'm trying to create more play at the bushing. There might be opportunities to accommodate both or a relocation, but you're right the tundra stuff could probably be used to riff on.

Don't you want the spacer to give support to the top of the bushings? It seems like, with just washers, the bushings will flex a lot more and possibly break.

I like where your mind is. I was partially testing the idea in quick and dirty fashion with wahsers to see if it would actually give me more flex. Figured some minor spacing was okay but I agree that the bushing may see more wear like this.

To your point, I was ginning up this idea of a tunable spacer bracket. Different durometer inserts could be added as support but also compliance. I have no intent to produce any of this but it was fun to play with and put the idea out there.

 

[lx200inAR]

I might have missed it but what I've seen are drop spacers that move everything down. I'm trying to create more play at the bushing. There might be opportunities to accommodate both or a relocation, but you're right the tundra stuff could probably be used to riff on.



I like where your mind is. I was partially testing the idea in quick and dirty fashion with wahsers to see if it would actually give me more flex. Figured some minor spacing was okay but I agree that the bushing may see more wear like this.

To your point, I was ginning up this idea of a tunable spacer bracket. Different durometer inserts could be added as support but also compliance. I have no intent to produce any of this but it was fun to play with and put the idea out there.

View attachment 3593800

View attachment 3593801

Maybe something for @PerryParts to look at 3d printing. I don’t know if there is enough thickness in the spacer for their process to create something pliable.

 

[FJRanger]

Sub’ed great ideas.

Wished my brain worked more like this. Hopefully, one of kids will fill this roll in the family.

 

[skrypj]

Applicability to KDSS​

Sway bar tuning could also benefit KDSS. In similar ways, but perhaps with additional benefits. It’s not spoken about much but there is mounting evidence where KDSS as applied to the 200-series can be a limitation in fast fire roads and baja type running. The 200-series KDSS is a stiff swaybar, with a passive mechanical system which has limits in its ability to decouple. It only unlocks in warp type situations where front and rear axles articulate out of phase. It’s otherwise engaged which takes some of the “independent” out of independent suspension, meaning if one tire hits something, it really affects the other one, and in turn has a greater effect on overall chassis motions. This isn't really a limitation in casual use, but hitting washboards and uneven terrain at over 40-50mph is where this shows.

KDSS has an internal accumulator that accommodates some small bump compliance which is why it's great at lower speeds. Later generations of KDSS, including several flavors of e-KDSS have computer controls to really disengage the sways at low speeds to maximized the ability of each wheel to respond more independently and minimizing transferring forces into the chassis. In later systems, there are kits to allow electronic manual overrides to fully disengage KDSS into higher speeds. It’s been shown that it creates better independent wheel response which has benefits to more comfortable and stable high speed running.

Utilizing the same strategies of shimming the sway bar chassis brackets can open it up to increase compliance for larger bumps and/or faster Baja style running.

My experience with KDSS on my GX460 was that it was great with slow crawling but if I was in 4hi and moving quickly on dirt roads where there was bumps and dips and stuff, the truck rode really stiff. This is more of where I spend my time/miles than true crawling situations.

Thats why I am not particularly upset about losing it with the LX570. Its kind of a novelty in my eyes and, honestly, I would rather just have a dedicated swaybar disconnect or simply pull off one end link when I intend to offroad. This is what I did with my F150. It would take me about 3 minutes to pop off the two nuts to remove the end link and then the truck would just float.

With an IFS/Solid rear axle truck, I would leave the rear bar connected to help force the front end to do more of the heavy lifting since the solid axle tends to be a bit more willing to articulate. If you look at any pictures of guys running "long travel" rear axle setups on the GX's, they get an insane amount of rear travel but they have to run with no sway bar. The front ends are barely doing anything with those super long softer progressive springs in the rear not really fighting the IFS to articulate.

 

[skrypj]

how much difference will a couple of mm of give at the bushings actually make at the bar ends? I imagine the side of the bar with the drooping tire will do what it normally does since it’s constrained by the stock bushing and bracket. The side with the compressed suspension will squish the softer rubber pad, but even if the pad is 5mm and it squishes 2mm, what’s that equate to at the tire? 6mm?

 

[daneo]

Applicability to KDSS​

KDSS has an internal accumulator that accommodates some small bump compliance which is why it's great at lower speeds. Later generations of KDSS, including several flavors of e-KDSS have computer controls to really disengage the sways at low speeds to maximized the ability of each wheel to respond more independently and minimizing transferring forces into the chassis. In later systems, there are kits to allow electronic manual overrides to fully disengage KDSS into higher speeds. It’s been shown that it creates better independent wheel response which has benefits to more comfortable and stable high speed running.

Utilizing the same strategies of shimming the sway bar chassis brackets can open it up to increase compliance for larger bumps and/or faster Baja style running.

A housekeeping note as this discussion of KDSS continues. It's worth checking the nomenclature of what "KDSS Engaged" means. Is it the sway bars actively resisting roll, or sway bars being manipulated to minimize their effect on roll and increase articulation?

In the GX and 4Runner implementations of KDSS, the ECU-controlled solenoids are able to allow or stop fluid flow into the accumulators. The main KDSS circuit is uninterrupted (circled in blue). When the solenoids are open, and fluid can flow into the accumulators, there is still immense pressure on the baffle in the accumulator. ~600PSI over several square inches. So the roll bar is still engaged, but with a greater level of compliance. In a way, it's similar to what you're doing with shimming the bushing.

I wouldn't say the GX/4R implementation is any more advanced than the 200 series KDSS. I think the 200 series has a more sophisticated system. I have a hunch that the fluid valving done mechanically on the 200 allows for a smooth transition between low speed, higher compliance and high speed lower compliance. Whereas, the GX/4R has a step function between the two modes. I will say, having the "high compliance" sway bar mode available at all times via a push button has its advantages

 

[bloc]

I believe the moderate speed lack of compliance with our mechanical KDSS system is a function of the small lines attempting to move the fluid around the system. Even with the mechanical valves allowed to limit pressure spikes, there is a practical limit on how quickly the fluid can get through the lines to the valve assembly, and that’ll end up resulting in higher pressures and less compliance at the cylinders.

Granted the flow rates are higher and lines are much smaller in relative terms, but when we pump a fire engine we may have to set a pressure at the unit 60, 80, maybe 100 psi higher than what you’d see at the nozzle to account for all the turbulence within the line before the water gets there. For perspective that means possibly doubling the pressure at the pump to get a given pressure at the nozzle. We call it friction loss, and it is a big factor in moving fluids through lines as the velocity increases. My gut tells me a hard hit on a stiff sway bar in a KDSS system means very high fluid velocities.

IIRC In the 300-series ekdss they put the valve hardware on the sway bar itself letting the fluid transfer right there and not need to travel all the way through the lines to the center of the vehicle. IMO that’s a critical design difference for the compliance some seek.

 

[skrypj]

I believe the moderate speed lack of compliance with our mechanical KDSS system is a function of the small lines attempting to move the fluid around the system. Even with the mechanical valves allowed to limit pressure spikes, there is a practical limit on how quickly the fluid can get through the lines to the valve assembly, and that’ll end up resulting in higher pressures and less compliance at the cylinders.

Granted the flow rates are higher and lines are much smaller in relative terms, but when we pump a fire engine we may have to set a pressure at the unit 60, 80, maybe 100 psi higher than what you’d see at the nozzle to account for all the turbulence within the line before the water gets there. For perspective that means possibly doubling the pressure at the pump to get a given pressure at the nozzle. We call it friction loss, and it is a big factor in moving fluids through lines as the velocity increases. My gut tells me a hard hit on a stiff sway bar in a KDSS system means very high fluid velocities.

IIRC In the 300-series ekdss they put the valve hardware on the sway bar itself letting the fluid transfer right there and not need to travel all the way through the lines to the center of the vehicle. IMO that’s a critical design difference for the compliance some seek.

That and EKDSS I believe has two pistons on each bar, doesnt it? So the bar floats to some degree instead of just pivoting around one bushing while they other end absorbs all the movement. If the side of the truck hitting a bump at speed is the side with the fixed swaybar bushing, it has to swing the whole bar.

 

[bloc]

That and EKDSS I believe has two pistons on each bar, doesnt it? So the bar floats to some degree instead of just pivoting around one bushing while they other end absorbs all the movement. If the side of the truck hitting a bump at speed is the side with the fixed swaybar bushing, it has to swing the whole bar.

From memory, on the 300-series yes I believe that is the case.

The single bushing scenario applies to 4Runner/GX KDSS, it not really for ours with the extra arm in front. The bar is mounted on two solid bushings like any other, it’s the fulcrum in the KDSS arm anchored to the end of the ram that decides whether any force from one side makes it to the other.

Hypothetically if we DCd the lines and left the ram open it would be like not having a sway bar.. but when the lines are there and we try to articulate quickly, there are limits to how quickly the fluid can reasonably move through the lines and that results in high pressures at the ram that the valve can’t effectively attenuate. (Edit: my theory, from having cut apart a valve)

 

[daneo]

That and EKDSS I believe has two pistons on each bar, doesnt it? So the bar floats to some degree instead of just pivoting around one bushing while they other end absorbs all the movement. If the side of the truck hitting a bump at speed is the side with the fixed swaybar bushing, it has to swing the whole bar.

Very little technical info in the vid, but confirms two loosey goosey chassis connections up front with a central pivot mount.

Out back looks to be one loosey goosey chassis connection and one hard connection similar to the 200 setup.

Still looks like fluid will flow between the two front hydraulic actuators. Assuming those lines are hydraulic and the loosey goosey parts are hydraulic rams.



Taking a swag at figuring out the operation of e-KDSS, the “e” must stand for electric pumps— one at the front, one at the rear, that build up the hydraulic pressure in the system on-demand? High pressure, the rams “lock out” and the sway bar resists sway. Low pressure and the rams can comply and reduce sway bar influence.

 

[bloc]

Very little technical info in the vid, but confirms two loosey goosey chassis connections up front with a central pivot mount.

Out back looks to be one loosey goosey chassis connection and one hard connection similar to the 200 setup.

Still looks like fluid will flow between the two front hydraulic actuators. Assuming those lines are hydraulic and the loosey goosey parts are hydraulic rams.



Taking a swag at figuring out the operation of e-KDSS, the “e” must stand for electric pumps— one at the front, one at the rear, that build up the hydraulic pressure in the system on-demand? High pressure, the rams “lock out” and the sway bar resists sway. Low pressure and the rams can comply and reduce sway bar influence.

I don’t think they’d need pumps, just valves to lock the fluid in place. With two rams and the pivot you describe up front, even if system pressure is elevated the rams can be plumbed to balance out and move relatively freely once the valves between them open up.

I also spy what seem to be a couple large accumulators in the rear valve assembly which makes sense to me, as without the rear ram being plumbed to another, you’d need something like that to deal with the pressure changes from the ram stroking in and out once the valves are opened up. That isn’t necessary with two rams up front that can cancel each other out on articulation.

 

[linuxgod]

Personally I’d use a piece of aluminum bar stock, not just washers, so the bracket is flush against the frame, but it’s a nice analysis you’ve done here.

Interestingly for those who do a KDSS relo bracket on their LC, it’s spacing the bushings down by 5/8” I think. It also pushes the forward 1” which has other implications on the sway bar angles.

Honestly for KDSS I want to push 1.5” out as I mount the sway bar end links on the front of the LCA, and they’re angled backwards a bit in my setup… less angle than if they are in the cradle, but still not ideal. I’ve been planning for a while to drill and tap some aluminum bar stock I bought to do that, so maybe I’ll give it a shot this spring. About my only real concerns in the LC case are how far forward can you go before the relo bracket is seeing too much stress and if it moves another 1/2” is there any chance of body mount or bull bar interference with the KDSS ram

 

[PerryParts]

Maybe something for @PerryParts to look at 3d printing. I don’t know if there is enough thickness in the spacer for their process to create something pliable.

I might have missed it but what I've seen are drop spacers that move everything down. I'm trying to create more play at the bushing. There might be opportunities to accommodate both or a relocation, but you're right the tundra stuff could probably be used to riff on.



I like where your mind is. I was partially testing the idea in quick and dirty fashion with wahsers to see if it would actually give me more flex. Figured some minor spacing was okay but I agree that the bushing may see more wear like this.

To your point, I was ginning up this idea of a tunable spacer bracket. Different durometer inserts could be added as support but also compliance. I have no intent to produce any of this but it was fun to play with and put the idea out there.

View attachment 3593800

View attachment 3593801

@TeCKis300 Could you please shoot me an email at patrick@perryparts.com? I've got a bushing concept that might be pretty neat to try here - if you're willing to be a beta tester!
@lx200inAR Thanks for the shoutout!

 

[AnyMal]

This over extending links? I think it's cleaner I like it. Very easy mod to do too.
@turbo8 I guess you got one buyer. I need to address this on my truck.