KDSS question
This is probably discussed somewhere but here goes....
I know KDSS is supposed to decrease body roll on road. But is it possible for KDSS to actually increase body roll at low speeds? I have a 19 TRD ORP with KDSS. I liked it when I test drove it (mostly on the interstate) - it seemed firmer and more controlled than the non-KDSS 4runners I have driven. But now that I own the car I’m experiencing it under different conditions. I’ve got a couple places in my work commute where I have to take a left turn at very low speeds, one of them coming off a bit of a hill. On both turns I notice very excessive body roll. I know various sensors, including speed sensors, are involved in engaging KDSS. Is it possible the system is just giving extra articulation in those instances since I’m going slow? The body roll is far greater than other trucks and SUVs I’ve driven on this same route. Since I’m new to KDSS I wanted to see if anyone else had similar experiences making low speed on-road turns. Is it something I need to get used or something I should check into? I’m on the stock Bridgestone tires, which I realize are pretty squishy. But I do have them at 35 psi. I look forward to replacing these tires with better ones eventually... Thanks. |
I guess I'm not fully understanding your question...
Usually a "turn at very low speeds" and "very excessive body roll" would be mutually exclusive. I have the exact same setup as you (2019 ORP w/KDSS) and haven't experienced any abnormal body roll on the street. |
KDSS is automatically engaged at any speed above 12 mph. Seems like you'd have to really work at it to take a corner sharply enough to induce body roll at a speed of less than 12 mph.
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What you're experiencing is what 4Runners without sway bars feel like. At very low speeds, KDSS is disengaged (very similar to not having sway bars), so you basically have a very tall vehicle making a turn without say bars. The KDSS isn't making your truck sway more, it just isn't doing anything to help it sway less. Make sense? So you have nothing to worry about, it is "normal" for our 4Runners that are equipped with KDSS and since you have to be going very slowly for this to happen, it should never be an issue.
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"is it possible for KDSS to actually increase body roll at low speeds?"
Yes. Not possible, but actually engineered that way. You basically have have no sway bars below 12 mph. |
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Here is how I interpret it.
The difference in a KDSS sway bar and a regular sway bar is that one end link / swing arm is replaced with a piston, on opposite sides front and rear. The hydraulics that drive the pistons is not pumped, but pushed from the piston that is being forced in at the opposite corner, through a balancing valve (accumulator) with electronics, to the piston that is extending. The sway bar does not disconnect, it just has further travel and dampening, and one endlink /swing arm is still present on each. Also, where is the engagement speed reference coming from? I have never seen that written, but i really havent looked either. My understanding of the system is that it engages when a wheel drops and force changes allowing the fluid to push to the extended cylinder. When you are driving on normal flat roads, the drops don't occur and pressures / forces are mostly equal. When i replaced my shocks, I had to unbolt the sway bars and raise and lower the pistons. It's really a pretty simple system aside from the electronics in the accumulator / valve. |
The KDSS computer also looks at steering angle and lateral acceleration, not just speed, so no the KDSS isn't increasing body roll
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Lots of bad info in this thread :(
This is as simple as I can make it: The KDSS sway bar has two hydraulic pistons (one front and one back) attached to the frame rail. These pistons become the 4th connecting point when charged/firm. When traveling at lower speeds/off road, the pistons un-charge/loosen, basically turning the sway bar into an unconnected flopping bar. This lets the suspension fully-travel (droop/compress) without causing opposite-side force via sway-bar. So, yes, when traveling at lower speeds, the pistons effectively stop the sway bars from doing their anti-sway job. At speeds below ~12 mph, this will make the driver perceive MORE body roll. It is engineered this way. This is why the model is called the "Trail or TRD OffRoad" model. Toyota assumes you want more articulation when you travel off road at low speeds. Understanding Sway Bar Technology - Tire Review Magazine Anti-roll bar - Wikipedia |
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Reading this thread and I don't own a KDSS 4runner... Grabbing my coffee and cookies for this one.
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[meme] someone is wrong on the internet [/meme]
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