That is actually a very important point. After such a catastrophic tire failure, an alignment check is in order.
Bad lean and pull after changing flat tire...... KDSS??
- Thread starter ggmanning
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Okay. If there's anyone following my thoughts on the KDSS operation I got my truck on ramps and took some pics of the cylinders to help people (and myself) understand things. I do intend to do a full thread with much more info eventually, but the following is why I think jacking up the truck from the frame to change a front flat is different than regular off-road articulation.
First, articulation, with the front left tire dropped out. The front left tire drooping pulls on the KDSS arm, while the main sway bar element is pushed up from the front right tire being stuffed, and the swaybar disconnect is accomplished by extending the front KDSS ram. This is only allowed because on the rear, the left rear tire is stuffed, which compresses the rear KDSS ram.
First, articulation, with the front left tire dropped out. The front left tire drooping pulls on the KDSS arm, while the main sway bar element is pushed up from the front right tire being stuffed, and the swaybar disconnect is accomplished by extending the front KDSS ram. This is only allowed because on the rear, the left rear tire is stuffed, which compresses the rear KDSS ram.
Now, the other side of articulation, the left front is stuffed. KDSS arm up, sway bar down from the right front dropped out, front KDSS ram must compress, and is allowed to by the rear KDSS ram extending. (I forgot to get a picture of the tape on the rear ram. It was approx 6.5" to the center of the bolt. You can barely see it extended)
Now we have the vehicle jacked up by the frame, lifting the front left tire off the ground. This kinda looks like normal articulation, in as much as that tire is drooped out. But the key difference is the front right and left rear are also dropped out because of the vehicle being jacked up, and the right rear is partially stuffed because of the jack under the other corner of the truck. Now KDSS is basically confused.. or, in a way, acts halfway between a corner and articulation. The rear axle is trying to twist the bar (right rear compressed, left rear dropped out), the front axle has the bar neutral (both fronts dropped out, especially the left).
You can see by the length of the front ram, it is nowhere near the lengths in earlier posts. Pay special attention to 2 above, where the front left is dropped out, but not as far as it can go due to the limited height of my ramps. With this tire now completely against the extension stop, the KDSS ram should be even longer than that post. It is shorter.
You can see by the length of the front ram, it is nowhere near the lengths in earlier posts. Pay special attention to 2 above, where the front left is dropped out, but not as far as it can go due to the limited height of my ramps. With this tire now completely against the extension stop, the KDSS ram should be even longer than that post. It is shorter.
With the rear bar trying to twist, and the front bar not, this is putting pressure on the KDSS system. No big deal right? Every time we take a corner the pressure between front & rear KDSS rams is what locks in the stabilizer bars and allows these pigs to handle relatively well on-road and still articulate enough when needed off-road to not be an Armada.
But, taking a corner is just a few seconds of force.. then things are neutral again. I suggest that if there is some kind of leak in the system.. say around the piston in one of the rams, or within the valve block on the frame.. this sustained force of the truck being jacked up long enough to change a flat could allow the system to become imbalanced.
I also think toyota designs these to accept slight leakage. If not leans could never fix themself. This may be why one parked on an incline can develop a lean. But.. say a ram is leaking more one way than the other.. that could, in my head, explain what happened here to OP.
Important note.. when you jack under the rear axle you are actually articulating the truck and none of this KDSS confusion applies.
This brings up something that occurred to me. Other than possible leans.. or a leak somewhere. How do we know the KDSS system is healthy and working as it should? How do we know one vehicle doesn't have some slop that leads to loose handling vs another? This is kindof a black-box system that most people don't mess with, ever.
I have some work planned on my truck soon and part of that will be disconnecting the sway bars and seeing if my truck still leans. No amount of loosening valves, driving around block, driving onto blocks, resetting valves, etc.. will cure my lean. I'm starting to wonder whether a lower arm got the bolts tightened in a position other than ride height.. or maybe the front bar having some preload from its mounting.
Then, the results of that will get posted in a new thread.
Also while under there I realized the bushings in my rear KDSS arm are pretty tired. Will be changing those as well. The one at the big end of the bar looks pretty tough to press out, on account of there not being much meat around it to grab with the press. Might have to cut the shell or something.
But, taking a corner is just a few seconds of force.. then things are neutral again. I suggest that if there is some kind of leak in the system.. say around the piston in one of the rams, or within the valve block on the frame.. this sustained force of the truck being jacked up long enough to change a flat could allow the system to become imbalanced.
I also think toyota designs these to accept slight leakage. If not leans could never fix themself. This may be why one parked on an incline can develop a lean. But.. say a ram is leaking more one way than the other.. that could, in my head, explain what happened here to OP.
Important note.. when you jack under the rear axle you are actually articulating the truck and none of this KDSS confusion applies.
This brings up something that occurred to me. Other than possible leans.. or a leak somewhere. How do we know the KDSS system is healthy and working as it should? How do we know one vehicle doesn't have some slop that leads to loose handling vs another? This is kindof a black-box system that most people don't mess with, ever.
I have some work planned on my truck soon and part of that will be disconnecting the sway bars and seeing if my truck still leans. No amount of loosening valves, driving around block, driving onto blocks, resetting valves, etc.. will cure my lean. I'm starting to wonder whether a lower arm got the bolts tightened in a position other than ride height.. or maybe the front bar having some preload from its mounting.
Then, the results of that will get posted in a new thread.
Also while under there I realized the bushings in my rear KDSS arm are pretty tired. Will be changing those as well. The one at the big end of the bar looks pretty tough to press out, on account of there not being much meat around it to grab with the press. Might have to cut the shell or something.
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I don't think that's necessary. Just look for lean afterward, and if it is now present, reset the valves and you should be good to go.
Well... my truck must be magic.
Every time I rotate my tires I jack each wheel up by the frame, take off the wheel/tire, put on a new wheel/tire and let it back down to the ground. I do this 4 times. Each wheel individually. Each jacked up by the frame. When jacking on the frame, each wheel is fully "dropped out."
Never had a lean.
Why don't I suffer the same KDSS weirdness being talked about here?
Every time I rotate my tires I jack each wheel up by the frame, take off the wheel/tire, put on a new wheel/tire and let it back down to the ground. I do this 4 times. Each wheel individually. Each jacked up by the frame. When jacking on the frame, each wheel is fully "dropped out."
Never had a lean.
Why don't I suffer the same KDSS weirdness being talked about here?
In off road situations, you are going to encounter all kinds of obstacles where only tire is articulating, and like @gaijin said if you work on your truck only jack up one (front for this example) wheel you're experiencing one wheel droop. I appreciate the effort @bloc is putting into this, but it just doesn't make sense. If a system like KDSS can cause major problems from jacking up a single wheel on a platform as robust as the 200, we're in trouble. But that's not the case as pointed out, and if it was the case your truck would be sitting a couple inches lower on one side after your experiment.
As I mentioned 2 posts above, it could be a problem with OPs truck that needed the forces involved in this condition to present itself.
As I mentioned a handful of times in this thread already, I'm not saying jacking by the frame is more than KDSS can handle or that we should avoid it or that it harms things. Just that it is not the same as normal off-road articulation.
It does make sense. You seem fixated on the concept of this being the same as what happens when we drive off-road, but it's not.
Jacking a vehicle up in this manner isn't even the same as your supposed one-wheel articulation.. the front right and left rear have drooped out due to the weight taken by the jack, and the right rear has been compressed.
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- #31
The jacking didnt cause my problem I dont think........the having to drive with the left front dropped down to the rim for 200yds to a safe stop point after it dropping out in 10 seconds at 60mph caused my issue. At least thats what I think. 800 miles later after calibrating my KDSS it's still perfect..