QUICK INTRO

On paper, active suspension systems like Lexus' AVS sound promising. In actual use, their effectiveness is ultimately limited to roads very close to those the system was programmed for. Rather unfortunately, this excludes roads where I'm from. Within about 5 minutes of local road driving, the rear dampers tend to aerate and lose their functionality, rendering AVS useless. Switching to beefier monotube dampers ought to keep things in check.

An active suspension delete means having to seal open factory plugs to prevent shorts. I went the extra mile for this, doing double heat shrinks on the plugs before tucking them away nicely. Unlike European vehicles, the removal of active dampers do not trigger errors in any of the NX's computers.

PARTS AND TOOLS NEEDED

2x Bilstein B6 P/N 24-282963

Peculiar things needed for this project:
- 17mm swivel ratchet box wrench
- 2 Heat shrink end caps with hotmelt inside like (AVS only)

Other tools you might already have:
- 10, 12, 17mm sockets
- 4 to 5" extension for the sockets
- Torque wrench (all 17mm bolts and nuts involved are torqued to 80 lb-ft)
- Gorilla tape (AVS only)
- Pliers (AVS only)
- Floor jack and jack stands

INSTALLATION


Factory AVS and Bilstein B6 rear dampers side by side.


AVS wire routing guide, in case things need to be reversed.


Upper bolt is tucked pretty deep. The upper mount is also angled in such a way to necessitate the use of a swivel head box wrench.


Electronic parking brake plug (A) and the 12mm bolt securing its wire mount (B) have to be removed before the upper damper bolt (C) can be loosened. Use a 17mm swivel ratchet box wrench.


Loosen (A) and (B) until you can freely spin their respective nuts by hand, then remove the 2 (C) bolts holding the lower bracket on to the control arm.


After removing the 2 (C) bolts. What made the removal of the lower bracket necessary is the position of the bolt on the damper's lower mount . It's angled in such a way that prevents the bolt from slipping out, should its loose nut completely come off. Some RAV4 folks flip this around for future convenience. While tedious, I recommend following the factory position for safety.


Remove AVS bracket with a 10mm socket. Reinstall nut.


Remove AVS bracket with a 10mm socket. The nut faces the center of the vehicle. Reinstall nut.


AVS plug ready to be unplugged. Once done, remove the upper bolt on the damper to slide the whole thing out.


Factory AVS and Bilstein B6 rear dampers side by side.


Bilstein B6 installed! All 17mm bolts are tightened to 80 lb-ft. Install the damper's top and bottom bolts loose first, then fully tighten the two bolts holding the lower bracket on to the lower arm. As the Bilstein dampers are slightly shorter in full extension, the lower control arm needs to be jacked up a bit to fully tighten the two bolts on the lower bracket. Without bringing the lower control arm back down, tighten the damper's lower bolt next. Lower the control arm and tighten the damper's upper bolt. UPDATE: The upper and lower damper bolts should be tightened at ride height, with the vehicle's weight on the tires. This avoids unnecessary harshness from preloaded damper bushings.Since a torque wrench wouldn't fit, tighten the upper bolt using a swivel head box wrench as far and hard as you can go.

SEALING AVS PLUGS


Vehicle-side AVS plug needs to be separated from the other wires. Remove the nut on the wire bracket closest to the AVS plug.


Open the metal bracket up to separate the AVS plug from the bracket. Reinstall bracket afterwards. Loosen the 10mm bolt on the wire bracket on the upper right side of the photo, so you can work on heat-shrinking the AVS plug further away from the fuel line. (This is a left side photo.)


Wrap with smooth, sticky, durable tape like Gorilla tape first. This will prevent the heat-shrink's hotmelt from getting into terminals and clips.


Heat-shrink end cap with hotmelt installed.


Heat-shrinked plug neatly tucked away and far from moving parts. (This is a right side photo.)

DONE!

INITIAL ROAD NOTES

These Bilstein B6 dampers are definitely not for everyone. I dove into this project knowing full well that the the B6s will be firmer than the factory dampers. The B4s are Bilstein's OEM-replacement line, after all. Even with the above in mind, the results were rather surprising.

The good:

- Greatly reduced repeat oscillations after hitting bumps
- Significant increase in high vehicle-speed, rough road stability and comfort
- Tail doesn't kick out as much when pushing hard out of corners (I have active bump stops installed.) = greater exit speeds
- Rear wheels readily extend down into potholes, so the body doesn't have to crash down.

The bad:

- Bump/compression damping is too stiff, likely due to the gas charge in monotube dampers being around 3x that of twin-tubes. (Maybe) this causes spring rates to temporarily increase as the damper settles to a new position, relative to the lower-pressure factory twin-tubes.
- Increase in low vehicle-speed harshness

I read around Euro vehicle forums and found two interesting points to consider:

- Some say B6s ride plusher after a few hundred mi/Km.
- Tightening the damper mounts with the vehicle up on stands will result in a rough ride, since the bushings will be preloaded.
- Reducing tire pressures can compensate for the firmer high frequency damping.

I'll work on the second point this weekend and report back in a few weeks.

DAY 3: The Bilstein dampers seem to have broken in a bit and are noticeably more compliant.

DAY 5: Loosening the upper and lower bolts on the dampers with all four tires loaded and bouncing the vehicle around 30 times before tightening them again definitely helped! The change was significant enough to turn this project from something I regret doing to something with performance-comfort trade-offs as I expected. Things can only get better from here. DIY updated accordingly.

MONTH 2: Comfortable. Perfect. The dampers have broken in and become very compliant while still being able to keep unnecessary side to side and up and down movements in check. Infinitely better than the factory AVS dampers in terms of comfort and grip. A slight bit of understeer on exit crept back into my setup, hinting that the rear tires are now sticking better. I will have to readjust my active bump stops to restore the handling balance I tuned in.

 

Have you tried eliminating the AVS in the front? It looks like they do not work so well for our roads here in the Philippines.

 

Initial road notes added.

Haven't tried that, as the front AVS struts are still able to cope with the 2.80 Kg/mm Tanabe NF210 springs in my vehicle.

The challenge I have with the front end is to find a way to add preload to recover some bump travel, thus increasing the amount of compression required before hitting my already-modified bump stops. I have a Whiteline 10mm polyurethane spacer stacked in the assembly to help, but even that's still inadequate. An easy fix is to switch to the taller-riding 3.51 Kg/mm RS-R front springs that came with my rear ones, but the 2.80 Kg/mm Tanabe fronts have been a great-handling pair to my rear springs so far.

 

What is the mileage of your car? I am bringing mine to the dealer to get the front suspension checked. It seems like the shock absorber is no longer working going speed bumps. Just like it is described in a different thread in this forum.

Also, where did you buy your springs from? Did they do the installation?

 

I have around 38k Km on her right now. If you are referring to the sensation that the front struts are overextending over speed bumps, then yes, I've noticed that since when my NX was new, 2015. At around 25k Km, I replaced all 4 AVS dampers with the 2018 and up ones but didn't see much improvement.

All my parts were bought online and shipped to the PH. Installation was mostly DIY as well. Working on the vehicle and test driving over the quarantine gave me years' worth of weekend testing in just a few months and proved to be a great way to pass time and get some physical activity.

 

Thanks for the feedback. I am planning to swap springs to get a better stance. Reading your reviews about the Tanabe and RSR is a big help in helping me decide which one to get.

 

You're welcome. I'm glad my posts helped. You can take your NX to FixStop up in QC. They did the first 2 or 3 spring changes on mine, before I started experimenting and doing things myself. Cheers