Kinetic Suspension - Is it all that?
03-10-05, 04:54 AM
#17
Lexus Test Driver
Originally Posted by tigmd99
Why does KDSS work on-road??
Well, KDSS starts out with THICKER anti-roll bars front and rear than regular GX...thus, allowing you to corner flat. More stability to crosswinds. However, it does make the ride a bit firmer (maybe bouncier?) over uneven small bumps, especially at high speed.
In off-road, KDSS hydrualically disconnects the anti-roll bars, thus allowing for more up-and-down motion of the wheels (front and rear), leading to more tires planted on the ground. This will help decrease ATRAC activation...more power to the ground and may save brake pad life.
If you have the $$, then get KDSS. It's a great technology that will be seen in more and more SUVs like Dodge Powerwagon and DHS system on Jeep GC. They are all similar systems in concept to KDSS.
Well, KDSS starts out with THICKER anti-roll bars front and rear than regular GX...thus, allowing you to corner flat. More stability to crosswinds. However, it does make the ride a bit firmer (maybe bouncier?) over uneven small bumps, especially at high speed.
In off-road, KDSS hydrualically disconnects the anti-roll bars, thus allowing for more up-and-down motion of the wheels (front and rear), leading to more tires planted on the ground. This will help decrease ATRAC activation...more power to the ground and may save brake pad life.
If you have the $$, then get KDSS. It's a great technology that will be seen in more and more SUVs like Dodge Powerwagon and DHS system on Jeep GC. They are all similar systems in concept to KDSS.
There is no mechanical disconnect of sway bars the moment you drive on dirt.
03-10-05, 04:59 AM
#18
Lexus Test Driver
Originally Posted by looknow12
Tigmd from what I've always read, the KDSS does not disconnect the sway bars when you drive off road. The KDSS's hydraulic system always allow the same side wheels to travel independently of each other, in fact it encourages it because as one wheel travels up, the hydraulic oil pressures the other wheel to travel down. The reason it works on road is because the body cannot lean too much. Because of the hydrualic pressure to both same side wheels. Off road it works well because when one wheel is depressed (traveled up) the other wheel which in conventional systems would hang, or have little weight on it, instead has force from the hydrualic pressure. So better distribution of weight makes for more tires with traction.
There is no mechanical disconnect of sway bars the moment you drive on dirt.
There is no mechanical disconnect of sway bars the moment you drive on dirt.
03-10-05, 05:17 AM
#19
Looknow, you could be right...but the effect of the hydraulics is equal to disconnecting the anti-roll bars. I do not think that KDSS push down the wheel that is up in the air...instead, the anti-roll bar "disconnects," thus allowing for more freedom in the wheel movement of both wheels on the axle. When this happens, the compressed wheel will compressed further up and the hanging wheel will hang lower down...thus, more wheel travel in BOTH wheels on the axle.
Here are some Lexus descriptions: (it's not clear enough to say that i am right or wrong.)
1.
Kinetic Dynamic Suspension System (KDSS)
The optional KDSS employs hydraulic controls for the front and rear stabilizer bars in order to improve on-road handling and enhance off-road capability.
The system uses hydraulic cylinders acting on each stabilizer bar that are linked by a pressure-sensing valve. During cornering, when both front and rear cylinders are compressed, no fluid is flowing in the system and the stabilizer bars work conventionally to reduce body roll.
However, when an uneven surface is encountered, one compressed cylinder causes fluid to flow between the front and rear cylinders, allowing the stabilizer bars to move freely. This increases wheel articulation and travel as well as helping to equalize wheel loading.
By allowing the stabilizer bars to disengage in certain situations, the stiffness of the stabilizers can be notably increased, thereby reducing body roll and improving handling without negatively effecting ride comfort or off-road performance.
2.
The KDSS technology, which has been proven in World Rally Championship (WRC) competitions, provides more sway stiffness when needed for crisp handling response, less sway resistance when cornering, more comfort over bumpy roads, and even disengages the stabilizers for some off-highway driving conditions. With the stabilizers disengaged, the suspension gains more travel and articulation to help handle obstacles. KDSS is the first such suspension system in an SUV to combine all of these dynamic control functions.
Here are some Lexus descriptions: (it's not clear enough to say that i am right or wrong.)
1.
Kinetic Dynamic Suspension System (KDSS)
The optional KDSS employs hydraulic controls for the front and rear stabilizer bars in order to improve on-road handling and enhance off-road capability.
The system uses hydraulic cylinders acting on each stabilizer bar that are linked by a pressure-sensing valve. During cornering, when both front and rear cylinders are compressed, no fluid is flowing in the system and the stabilizer bars work conventionally to reduce body roll.
However, when an uneven surface is encountered, one compressed cylinder causes fluid to flow between the front and rear cylinders, allowing the stabilizer bars to move freely. This increases wheel articulation and travel as well as helping to equalize wheel loading.
By allowing the stabilizer bars to disengage in certain situations, the stiffness of the stabilizers can be notably increased, thereby reducing body roll and improving handling without negatively effecting ride comfort or off-road performance.
2.
The KDSS technology, which has been proven in World Rally Championship (WRC) competitions, provides more sway stiffness when needed for crisp handling response, less sway resistance when cornering, more comfort over bumpy roads, and even disengages the stabilizers for some off-highway driving conditions. With the stabilizers disengaged, the suspension gains more travel and articulation to help handle obstacles. KDSS is the first such suspension system in an SUV to combine all of these dynamic control functions.
Last edited by tigmd99; 03-10-05 at 05:21 AM.
03-10-05, 05:19 AM
#20
Here is some more description:
Proven in the World Rally Championship, the innovative KDSS is a global first for production vehicles. The system offers significant benefits in ride, handling and traction that can be felt in a wide variety of driving conditions -- on and off-road -- by employing a simple hydraulic control system acting on both front and rear stabilizer bars.
KDSS varies the degree of roll stiffness provided by each of the stabilizer bars in response to changing road conditions and driver inputs, but rather than increasing roll stiffness, the system reduces it as conditions require. With its variable roll stiffness, a KDSS-equipped GX 470 is able to use much larger stabilizer bars that help reduce maximum body roll angle by nearly 50 percent, significantly improving handling response.
Large stabilizer bars would normally mean a stiff ride over single-wheel bumps, but with KDSS, the energy is distributed between front and rear so that ride comfort is not disturbed. In some cases it's actually better. Larger stabilizer bars also mean that shock absorber damping force can be better optimized to improve ride comfort, without sacrificing handling.
The front and rear stabilizer bars, which have nearly double the standard torsional stiffness, are supported by their own inter-connecting hydraulic cylinders. In normal cornering, the bars work conventionally to resist body roll motion and there is no fluid flow between the cylinders. But when unequal wheel loading occurs in certain conditions, fluid can move between the front and rear cylinders, helping to equalize loading.
The constantly changing and variable terrain that's typical of most off- road situations highlights the benefits of KDSS. Stiff stabilizer bars can limit off-road performance because the inside wheels tend to lift and lose traction when outside wheels encounter bumps. But with KDSS, the hydraulic cylinders allow the wheels on each axle to move with a larger degree of side- to-side independence, minimizing any tendency for wheel lift. The increased suspension articulation freedom helps maximize traction, even in the most challenging off-road driving situations.
KDSS works in concert with Adaptive Variable Suspension (AVS), which continuously changes shock absorber damping in response to road conditions and driver input. Combining these suspension technologies helps provide superior ride and handling and maximum traction both on and off-road.
Proven in the World Rally Championship, the innovative KDSS is a global first for production vehicles. The system offers significant benefits in ride, handling and traction that can be felt in a wide variety of driving conditions -- on and off-road -- by employing a simple hydraulic control system acting on both front and rear stabilizer bars.
KDSS varies the degree of roll stiffness provided by each of the stabilizer bars in response to changing road conditions and driver inputs, but rather than increasing roll stiffness, the system reduces it as conditions require. With its variable roll stiffness, a KDSS-equipped GX 470 is able to use much larger stabilizer bars that help reduce maximum body roll angle by nearly 50 percent, significantly improving handling response.
Large stabilizer bars would normally mean a stiff ride over single-wheel bumps, but with KDSS, the energy is distributed between front and rear so that ride comfort is not disturbed. In some cases it's actually better. Larger stabilizer bars also mean that shock absorber damping force can be better optimized to improve ride comfort, without sacrificing handling.
The front and rear stabilizer bars, which have nearly double the standard torsional stiffness, are supported by their own inter-connecting hydraulic cylinders. In normal cornering, the bars work conventionally to resist body roll motion and there is no fluid flow between the cylinders. But when unequal wheel loading occurs in certain conditions, fluid can move between the front and rear cylinders, helping to equalize loading.
The constantly changing and variable terrain that's typical of most off- road situations highlights the benefits of KDSS. Stiff stabilizer bars can limit off-road performance because the inside wheels tend to lift and lose traction when outside wheels encounter bumps. But with KDSS, the hydraulic cylinders allow the wheels on each axle to move with a larger degree of side- to-side independence, minimizing any tendency for wheel lift. The increased suspension articulation freedom helps maximize traction, even in the most challenging off-road driving situations.
KDSS works in concert with Adaptive Variable Suspension (AVS), which continuously changes shock absorber damping in response to road conditions and driver input. Combining these suspension technologies helps provide superior ride and handling and maximum traction both on and off-road.
03-10-05, 05:22 AM
#21
Originally Posted by PitBull
Anyone know how the Xreas shock system compares with the KDSS from a ride and handling standpoint?
On-road, they are probably similar in effect. Off-road, KDSS is superior. This kinda strange because there are more 4runner owners who take their truck off-road than GX owners...so, Toyota/Lexus should have switched the system. Of course, XREAS is not compatible with the electronic gas shocks (adaptive suspension--computer varies dampening rate on shock valve) on the GX...so that may be the reason why GX got the KDSS system.
Last edited by tigmd99; 03-10-05 at 05:43 AM.
03-10-05, 07:15 AM
#22
Lexus Test Driver
Originally Posted by tigmd99
Looknow, you could be right...but the effect of the hydraulics is equal to disconnecting the anti-roll bars. I do not think that KDSS push down the wheel that is up in the air...instead, the anti-roll bar "disconnects," thus allowing for more freedom in the wheel movement of both wheels on the axle.
03-10-05, 07:21 AM
#23
Lexus Test Driver
Originally Posted by tigmd99
Large stabilizer bars would normally mean a stiff ride over single-wheel bumps, but with KDSS, the energy is distributed between front and rear so that ride comfort is not disturbed. In some cases it's actually better. Larger stabilizer bars also mean that shock absorber damping force can be better optimized to improve ride comfort, without sacrificing handling.
Originally Posted by tigmd99
The front and rear stabilizer bars, which have nearly double the standard torsional stiffness, are supported by their own inter-connecting hydraulic cylinders. In normal cornering, the bars work conventionally to resist body roll motion and there is no fluid flow between the cylinders. But when unequal wheel loading occurs in certain conditions, fluid can move between the front and rear cylinders, helping to equalize loading.
Originally Posted by tigmd99
The constantly changing and variable terrain that's typical of most off- road situations highlights the benefits of KDSS. Stiff stabilizer bars can limit off-road performance because the inside wheels tend to lift and lose traction when outside wheels encounter bumps. But with KDSS, the hydraulic cylinders allow the wheels on each axle to move with a larger degree of side- to-side independence, minimizing any tendency for wheel lift. The increased suspension articulation freedom helps maximize traction, even in the most challenging off-road driving situations.
KDSS works in concert with Adaptive Variable Suspension (AVS), which continuously changes shock absorber damping in response to road conditions and driver input. Combining these suspension technologies helps provide superior ride and handling and maximum traction both on and off-road.
KDSS works in concert with Adaptive Variable Suspension (AVS), which continuously changes shock absorber damping in response to road conditions and driver input. Combining these suspension technologies helps provide superior ride and handling and maximum traction both on and off-road.
03-10-05, 12:01 PM
#25
Lexus Test Driver
Originally Posted by tigmd99
Looknow, i am pretty sure that KDSS does not connect front-to-rear. It acts on the anti-roll bars (both front and rear).
The front and rear stabilizer bars, which have nearly double the standard torsional stiffness, are supported by their own inter-connecting hydraulic cylinders. In normal cornering, the bars work conventionally to resist body roll motion and there is no fluid flow between the cylinders. But when unequal wheel loading occurs in certain conditions, fluid can move between the front and rear cylinders, helping to equalize loading.
But I'm not 100% positive.
03-10-05, 03:15 PM
#26
Originally Posted by looknow12
That's how I interpret this.
The front and rear stabilizer bars, which have nearly double the standard torsional stiffness, are supported by their own inter-connecting hydraulic cylinders. In normal cornering, the bars work conventionally to resist body roll motion and there is no fluid flow between the cylinders. But when unequal wheel loading occurs in certain conditions, fluid can move between the front and rear cylinders, helping to equalize loading.
But I'm not 100% positive.
The front and rear stabilizer bars, which have nearly double the standard torsional stiffness, are supported by their own inter-connecting hydraulic cylinders. In normal cornering, the bars work conventionally to resist body roll motion and there is no fluid flow between the cylinders. But when unequal wheel loading occurs in certain conditions, fluid can move between the front and rear cylinders, helping to equalize loading.
But I'm not 100% positive.
I took a look at what the XREAS does and what I know about KDSS (and there ARE three different types of kinetic suspension - the Lexus apparently using something called RFS or reverse function stablizer). They are not that similar in concept. The major difference is that XREAS uses the shock absorber loading to compensate for roll, by using the opposing corners to pressure shift between shock absorbers (which is a poor substitute for a heavy stabilizing sway bar). This may keep the body roll somewhat less, but it is an inferior system to the Kinetic type. It also decreases ride impact cushion when in that condition.
The KDSS system uses hydraulic pistons, on the sway bar, which are linked to the wheels on the SAME sides of the truck (Front to Rear). The Front and Rear sway bars are spit into two pieces linked by a "rotational" pivot, with a piston "locking" possible rotation at that point. To give you an idea, if you are making a hard right turn at high speed you get the following: During the turn, the entire Right side is trying to lean away from the wheels and twist the sway bars. This cannot happen because the Front/Back coincident movement of the right side lifting, pressurizing the hydraulic fluid between the front and back pistons equally, thereby locking the sway bar sections together and body roll is reduced (as a 2" sway bar would dictate). Now, you take that same function in an offroad situation and you get this: If the truck has opposing (counter-corner) wheel travel, the pistons, having different pressures. The pressure difference would allow some rotation (fluid moving front pistion to back piston or vice-versa) to equalize the pressure. The equalization of pressure would stop the movement at the rotational pivot. This only happens when the wheels on the same side have different amounts of pressure (ride heights) on the torsion bar pistons. And all of this happens, without effecting the cushion the shock absorbers are "supposed" to be doing.
Anyway, I hope this helps. I have the KDSS, and I have to say that it makes a huge difference in the handling of the truck, in cornering at speed or OFF road. I would find it hard to believe someone cannot tell the difference between having it and not having it. If you can't tell the difference, I think you should stay away from any kind of performance racing (on or off road). my .02
03-11-05, 02:52 AM
#27
Lexus Test Driver
Originally Posted by ADVocate
I am not the designer, so don't shoot me if my description sounds confusing. The way I understand these concepts is the following:
I took a look at what the XREAS does and what I know about KDSS (and there ARE three different types of kinetic suspension - the Lexus apparently using something called RFS or reverse function stablizer). They are not that similar in concept. The major difference is that XREAS uses the shock absorber loading to compensate for roll, by using the opposing corners to pressure shift between shock absorbers (which is a poor substitute for a heavy stabilizing sway bar). This may keep the body roll somewhat less, but it is an inferior system to the Kinetic type. It also decreases ride impact cushion when in that condition.
The KDSS system uses hydraulic pistons, on the sway bar, which are linked to the wheels on the SAME sides of the truck (Front to Rear). The Front and Rear sway bars are spit into two pieces linked by a "rotational" pivot, with a piston "locking" possible rotation at that point. To give you an idea, if you are making a hard right turn at high speed you get the following: During the turn, the entire Right side is trying to lean away from the wheels and twist the sway bars. This cannot happen because the Front/Back coincident movement of the right side lifting, pressurizing the hydraulic fluid between the front and back pistons equally, thereby locking the sway bar sections together and body roll is reduced (as a 2" sway bar would dictate). Now, you take that same function in an offroad situation and you get this: If the truck has opposing (counter-corner) wheel travel, the pistons, having different pressures. The pressure difference would allow some rotation (fluid moving front pistion to back piston or vice-versa) to equalize the pressure. The equalization of pressure would stop the movement at the rotational pivot. This only happens when the wheels on the same side have different amounts of pressure (ride heights) on the torsion bar pistons. And all of this happens, without effecting the cushion the shock absorbers are "supposed" to be doing.
I took a look at what the XREAS does and what I know about KDSS (and there ARE three different types of kinetic suspension - the Lexus apparently using something called RFS or reverse function stablizer). They are not that similar in concept. The major difference is that XREAS uses the shock absorber loading to compensate for roll, by using the opposing corners to pressure shift between shock absorbers (which is a poor substitute for a heavy stabilizing sway bar). This may keep the body roll somewhat less, but it is an inferior system to the Kinetic type. It also decreases ride impact cushion when in that condition.
The KDSS system uses hydraulic pistons, on the sway bar, which are linked to the wheels on the SAME sides of the truck (Front to Rear). The Front and Rear sway bars are spit into two pieces linked by a "rotational" pivot, with a piston "locking" possible rotation at that point. To give you an idea, if you are making a hard right turn at high speed you get the following: During the turn, the entire Right side is trying to lean away from the wheels and twist the sway bars. This cannot happen because the Front/Back coincident movement of the right side lifting, pressurizing the hydraulic fluid between the front and back pistons equally, thereby locking the sway bar sections together and body roll is reduced (as a 2" sway bar would dictate). Now, you take that same function in an offroad situation and you get this: If the truck has opposing (counter-corner) wheel travel, the pistons, having different pressures. The pressure difference would allow some rotation (fluid moving front pistion to back piston or vice-versa) to equalize the pressure. The equalization of pressure would stop the movement at the rotational pivot. This only happens when the wheels on the same side have different amounts of pressure (ride heights) on the torsion bar pistons. And all of this happens, without effecting the cushion the shock absorbers are "supposed" to be doing.
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