Air Suspension to Standard Conversion?
12-05-11, 11:19 AM
#46
Lexus Test Driver
Seems like there are quite a few threads here on suspension issues. Additionally, the LX forum has a number of threads on suspension issues. The Adaptive Variable Suspension (AVS) is found in mid to large Lexus and Toyota SUVs. While it may or may not affect the larger population of owners, no advance suspension system is "perfect" and not subject to some % of failure.
12-05-11, 11:35 AM
#47
This is a good summary.
What I am feeling is not "bottoming out" or hitting the bump stops. What I feel is poor rebounding dampening. It's best descrived as hard bottoming when I go over a sharp speed bump, but again my shocks are not bottoming out, not even close. The shock compresses, the rear of the truck rises and I assume the leveling suspension starts to try and level the rear end at this point and starts filling the bag. Once the rear wheel comes down off of the bump, the shock extends, the rear end comes down, but doesn't bounce or sag, it stays level, and bam, hard bottom. It feels to me like the rear leveling suspension is over reacting to the speed bumps and by the time my truck comes off the bump the bag is arleady filled with air resulting in the poor rebounding dampening.
The suspension is set to the 2nd most comfortable position. On comfort the suspension is less prone to exhibit this behavior. My GX sits even, the air/leveling suspension appears to be funcition correctly, adjusts to the slightest weight added to the back or vice versa. Other than the hard bottoming issue it rides great. Perhaps bad compression valves in the shocks?
What I am feeling is not "bottoming out" or hitting the bump stops. What I feel is poor rebounding dampening. It's best descrived as hard bottoming when I go over a sharp speed bump, but again my shocks are not bottoming out, not even close. The shock compresses, the rear of the truck rises and I assume the leveling suspension starts to try and level the rear end at this point and starts filling the bag. Once the rear wheel comes down off of the bump, the shock extends, the rear end comes down, but doesn't bounce or sag, it stays level, and bam, hard bottom. It feels to me like the rear leveling suspension is over reacting to the speed bumps and by the time my truck comes off the bump the bag is arleady filled with air resulting in the poor rebounding dampening.
The suspension is set to the 2nd most comfortable position. On comfort the suspension is less prone to exhibit this behavior. My GX sits even, the air/leveling suspension appears to be funcition correctly, adjusts to the slightest weight added to the back or vice versa. Other than the hard bottoming issue it rides great. Perhaps bad compression valves in the shocks?
I've got mine set now such that I only touch the bumpstops on *big* plateau speed bumps.
12-05-11, 11:36 AM
#48
12-05-11, 12:08 PM
#49
Lexus Test Driver
Have you checked the "contact point" where the bump stops contact the axle? My bet is they're clean (meaning you've got frequent contact), and you're bouncing off the bump stops, which will "bounce" the rear of the truck up and exacerbate weak rebound damping.
I've got mine set now such that I only touch the bumpstops on *big* plateau speed bumps.
I've got mine set now such that I only touch the bumpstops on *big* plateau speed bumps.
12-05-11, 01:27 PM
#50
Have you checked the "contact point" where the bump stops contact the axle? My bet is they're clean (meaning you've got frequent contact), and you're bouncing off the bump stops, which will "bounce" the rear of the truck up and exacerbate weak rebound damping.
I've got mine set now such that I only touch the bumpstops on *big* plateau speed bumps.
I've got mine set now such that I only touch the bumpstops on *big* plateau speed bumps.
The rear of my truck doesn't "bounce" up after compression, which would be indicative of my shock lacking rebound control. It's only after the shock compresses and then rebounds does it seem like the shock will not compress again to absorb the shock when coming off a speed bump let's say.
12-05-11, 02:40 PM
#51
Lexus Test Driver
No not yet but will try to look tonight. I assume I can see it without jacking up the truck? I would be surprised if the rear of my truck was dropping low enough to come into contact with the bump stops, the shocks just don't allow it to drop that low and they shouldn't.
The rear of my truck doesn't "bounce" up after compression, which would be indicative of my shock lacking rebound control. It's only after the shock compresses and then rebounds does it seem like the shock will not compress again to absorb the shock when coming off a speed bump let's say.
The rear of my truck doesn't "bounce" up after compression, which would be indicative of my shock lacking rebound control. It's only after the shock compresses and then rebounds does it seem like the shock will not compress again to absorb the shock when coming off a speed bump let's say.
12-05-11, 05:01 PM
#52
Not any time soon, unfortunately. Once you get under the back of the truck and have a clear view of the axle, it's pretty obvious.
There are two bump stops, one on either side. IIRC they're "inboard" from the point where the control arms attach to the axle. They "hang down" from the underbody/chassis and end with a rubber bumper that's probably 2-3" thick.
There are two bump stops, one on either side. IIRC they're "inboard" from the point where the control arms attach to the axle. They "hang down" from the underbody/chassis and end with a rubber bumper that's probably 2-3" thick.
12-05-11, 05:40 PM
#53
Originally Posted by CSSNMS
Originally Posted by cssnms
No not yet but will try to look tonight. I assume I can see it without jacking up the truck? I would be surprised if the rear of my truck was dropping low enough to come into contact with the bump stops, the shocks just don't allow it to drop that low and they shouldn't.
The rear of my truck doesn't "bounce" up after compression, which would be indicative of my shock lacking rebound control. It's only after the shock compresses and then rebounds does it seem like the shock will not compress again to absorb the shock when coming off a speed bump let's say.
No not yet but will try to look tonight. I assume I can see it without jacking up the truck? I would be surprised if the rear of my truck was dropping low enough to come into contact with the bump stops, the shocks just don't allow it to drop that low and they shouldn't.
The rear of my truck doesn't "bounce" up after compression, which would be indicative of my shock lacking rebound control. It's only after the shock compresses and then rebounds does it seem like the shock will not compress again to absorb the shock when coming off a speed bump let's say.
A couple things:
- the shocks don't have anything to do with "static" ride height. This is controlled by the air spring.
- the shocks *do* strongly influence how far the axle moves based on a particular event. The "compression" damping controls how easily the shock can compress. Or, in other words, how far the rear axle is going to move "up into the body" when it hits a speed bump, or when it comes down off of the rebound from a speed bump. The "rebound" damping controls how freely the spring gets to "bounce" the truck "up" after compression.
The more worn the shock, the less it is able to control (aka "damp/dampen") a given movement of the axle. This is why the truck is more likely to come in contact with the bump stops when the shocks are worn -- the axle is moving more based on the same inputs with a worn shock.
Shocks wear gradually over time, unless you have a catastrophic seal failure. My new rear shocks were far tougher to compress than the old ones I took off at 60k miles. Not scientific, just the "how hard is it to compress this thing" test.
Finally, the other variable that comes into play here is ride height adjustment. You can tweak the rear of the truck "up" to try to keep it off of the bump stops, but you fairly quickly run into an issue of stiffening the rear air springs and worsening the ride for other reasons.
Sorry, no more long posts tonight
12-08-11, 07:37 PM
#54
Instructor
I think I screwed up the multi-quote above. Hope this works...
A couple things:
- the shocks don't have anything to do with "static" ride height. This is controlled by the air spring.
- the shocks *do* strongly influence how far the axle moves based on a particular event. The "compression" damping controls how easily the shock can compress. Or, in other words, how far the rear axle is going to move "up into the body" when it hits a speed bump, or when it comes down off of the rebound from a speed bump. The "rebound" damping controls how freely the spring gets to "bounce" the truck "up" after compression.
The more worn the shock, the less it is able to control (aka "damp/dampen") a given movement of the axle. This is why the truck is more likely to come in contact with the bump stops when the shocks are worn -- the axle is moving more based on the same inputs with a worn shock.
Shocks wear gradually over time, unless you have a catastrophic seal failure. My new rear shocks were far tougher to compress than the old ones I took off at 60k miles. Not scientific, just the "how hard is it to compress this thing" test.
Finally, the other variable that comes into play here is ride height adjustment. You can tweak the rear of the truck "up" to try to keep it off of the bump stops, but you fairly quickly run into an issue of stiffening the rear air springs and worsening the ride for other reasons.
Sorry, no more long posts tonight
A couple things:
- the shocks don't have anything to do with "static" ride height. This is controlled by the air spring.
- the shocks *do* strongly influence how far the axle moves based on a particular event. The "compression" damping controls how easily the shock can compress. Or, in other words, how far the rear axle is going to move "up into the body" when it hits a speed bump, or when it comes down off of the rebound from a speed bump. The "rebound" damping controls how freely the spring gets to "bounce" the truck "up" after compression.
The more worn the shock, the less it is able to control (aka "damp/dampen") a given movement of the axle. This is why the truck is more likely to come in contact with the bump stops when the shocks are worn -- the axle is moving more based on the same inputs with a worn shock.
Shocks wear gradually over time, unless you have a catastrophic seal failure. My new rear shocks were far tougher to compress than the old ones I took off at 60k miles. Not scientific, just the "how hard is it to compress this thing" test.
Finally, the other variable that comes into play here is ride height adjustment. You can tweak the rear of the truck "up" to try to keep it off of the bump stops, but you fairly quickly run into an issue of stiffening the rear air springs and worsening the ride for other reasons.
Sorry, no more long posts tonight
12-08-11, 10:30 PM
#55
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Here's the odd part - when I had my bottoming-out issue, Lexus replaced my ride height sensors as well as my shocks. Then when it still wasn't quite good, they re-adjusted it on the ground vs. up on the rack. Then, most recently, the bags themselves were replaced completely.
At this point, the "bottoming-out" still occurs and I've got sensors and shocks that are only 18 months old, and bags that are only 6 months old - essentially, it's an entirely-new system.
In another thread, I did see where someone had mentioned adjusting the ride height so the neutral setting were actually set a bit higher and that supposedly did the trick.
As for me, I continue to cycle my height to the top setting only, then let it settle to neutral automatically as I drive off and exceed 20mph. I've found it's the only way to minimize the bottoming-out sensation over speed bumps and other dips, although the occasional deep dip in freeway section couplings occasionally sees the bottoming-out occur at 70mph or above.
At this point, the "bottoming-out" still occurs and I've got sensors and shocks that are only 18 months old, and bags that are only 6 months old - essentially, it's an entirely-new system.
In another thread, I did see where someone had mentioned adjusting the ride height so the neutral setting were actually set a bit higher and that supposedly did the trick.
As for me, I continue to cycle my height to the top setting only, then let it settle to neutral automatically as I drive off and exceed 20mph. I've found it's the only way to minimize the bottoming-out sensation over speed bumps and other dips, although the occasional deep dip in freeway section couplings occasionally sees the bottoming-out occur at 70mph or above.
12-09-11, 03:11 AM
#56
Lexus Test Driver
Here's the odd part - when I had my bottoming-out issue, Lexus replaced my ride height sensors as well as my shocks. Then when it still wasn't quite good, they re-adjusted it on the ground vs. up on the rack. Then, most recently, the bags themselves were replaced completely.
At this point, the "bottoming-out" still occurs and I've got sensors and shocks that are only 18 months old, and bags that are only 6 months old - essentially, it's an entirely-new system.
In another thread, I did see where someone had mentioned adjusting the ride height so the neutral setting were actually set a bit higher and that supposedly did the trick.
As for me, I continue to cycle my height to the top setting only, then let it settle to neutral automatically as I drive off and exceed 20mph. I've found it's the only way to minimize the bottoming-out sensation over speed bumps and other dips, although the occasional deep dip in freeway section couplings occasionally sees the bottoming-out occur at 70mph or above.
At this point, the "bottoming-out" still occurs and I've got sensors and shocks that are only 18 months old, and bags that are only 6 months old - essentially, it's an entirely-new system.
In another thread, I did see where someone had mentioned adjusting the ride height so the neutral setting were actually set a bit higher and that supposedly did the trick.
As for me, I continue to cycle my height to the top setting only, then let it settle to neutral automatically as I drive off and exceed 20mph. I've found it's the only way to minimize the bottoming-out sensation over speed bumps and other dips, although the occasional deep dip in freeway section couplings occasionally sees the bottoming-out occur at 70mph or above.
Wow, you had the height sensors and shocks replaced? Were they replaced under warranty? Mann777 mentioned the "Pneumatic Cylinder Weak ( Solenoid Assy " as most likely problem:
https://www.clublexus.com/forums/gx-...mp-stop-2.html
Perhaps this could be the next item to replace, if you're still under warranty.
12-12-11, 05:58 AM
#57
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Here's the odd part - when I had my bottoming-out issue, Lexus replaced my ride height sensors as well as my shocks. Then when it still wasn't quite good, they re-adjusted it on the ground vs. up on the rack. Then, most recently, the bags themselves were replaced completely.
At this point, the "bottoming-out" still occurs and I've got sensors and shocks that are only 18 months old, and bags that are only 6 months old - essentially, it's an entirely-new system.
In another thread, I did see where someone had mentioned adjusting the ride height so the neutral setting were actually set a bit higher and that supposedly did the trick.
As for me, I continue to cycle my height to the top setting only, then let it settle to neutral automatically as I drive off and exceed 20mph. I've found it's the only way to minimize the bottoming-out sensation over speed bumps and other dips, although the occasional deep dip in freeway section couplings occasionally sees the bottoming-out occur at 70mph or above.
At this point, the "bottoming-out" still occurs and I've got sensors and shocks that are only 18 months old, and bags that are only 6 months old - essentially, it's an entirely-new system.
In another thread, I did see where someone had mentioned adjusting the ride height so the neutral setting were actually set a bit higher and that supposedly did the trick.
As for me, I continue to cycle my height to the top setting only, then let it settle to neutral automatically as I drive off and exceed 20mph. I've found it's the only way to minimize the bottoming-out sensation over speed bumps and other dips, although the occasional deep dip in freeway section couplings occasionally sees the bottoming-out occur at 70mph or above.
12-12-11, 12:28 PM
#58
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N305AS,
Wow, you had the height sensors and shocks replaced? Were they replaced under warranty? Mann777 mentioned the "Pneumatic Cylinder Weak ( Solenoid Assy " as most likely problem:
https://www.clublexus.com/forums/gx-...mp-stop-2.html
Perhaps this could be the next item to replace, if you're still under warranty.
Wow, you had the height sensors and shocks replaced? Were they replaced under warranty? Mann777 mentioned the "Pneumatic Cylinder Weak ( Solenoid Assy " as most likely problem:
https://www.clublexus.com/forums/gx-...mp-stop-2.html
Perhaps this could be the next item to replace, if you're still under warranty.
12-12-11, 08:44 PM
#59
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12-12-11, 09:27 PM
#60
Finally I was able to locate the TSB..here is the one lexus used for 2003/2004 models. Maybe 05 year models could use this as a bottomline if all other troubleshooting have been resolved.
Furhter more I have added the Power Distribution for the Fuse location and Relay Location if needed be. cheers
Furhter more I have added the Power Distribution for the Fuse location and Relay Location if needed be. cheers