AHC harsh ride after shock replacement (1 Viewer)

[Blekansikt]

Dear Forum,
I seek knowledge- and experience based input: As a consequence of sandblasting mishap, we have replaced both front shocks on our VDJ200 w AHC. Vehicle mileage is 225k km, front shocks are now 12k km. On first ride w new front shocks I immediately noticed a harsher ride and an unbalance between front and rear. Rear feels a lot softer, maybe like it used to be. Before the change all three settings were usable. After the change Soft is firmer than Sport used to be. There is no point at all in using normal and Sport. It feels like anti dive is constantly active. Initially I hoped the feel would change as the shocks break in, but so far not. The workshop is quite good, but do not see many 200's pr year. They will look at the car again, fullt open that they will have to learn from this.

Has anyone input to this situation?

-A

 

[radman]

You might have air in the system. What did they do with the fluid after the shocks were replaced?

 

[Blekansikt]

You might have air in the system. What did they do with the fluid after the shocks were replaced?

Tnx for quick responce!

According to what they said, they bled it. Height adjustment works fine, quicker than before. But yeah, I guess there can be air trapped in damping force control actuator or spring rate switching valve without that effecting height adjustment noticeably. You have similar experince?

 

[TeCKis300]

Replacing front AHC shocks is a relatively straightforward affair as I somewhat went through the process recently installing an OEM front spacer (which requires removing the shocks). Bleeding is reasonably straightforward too, and the system seems to bleed itself to some extent after cycling through heights multiple times.

If the systems is cycling in heights just fine, I'd suspect something else.

Ask them if they torqued the lower control arms with the full weight of the vehicle on the suspension. (LCA and sway bar)

I suspect, as many shops cheat and do, that they torque the suspension at full droop. This causes the bushings in the control arms to be pre-loaded at ride height. OEM suspensions use fixed and bonded rubber bushings that depend on deformation for suspension travel. So if it's torqued at full droop, it will be pre-loaded, and add to perceived spring rate. They might get away with this on normal cars, but our cruisers have massive suspension travel causing the bushings to really bind. This is also a great way to have them prematurely fail.

May also want to check tire pressures?

 

[Blekansikt]

Replacing front AHC shocks is a relatively straightforward affair as I somewhat went through the process recently installing an OEM front spacer (which requires removing the shocks). Bleeding is reasonably straightforward too, and the system seems to bleed itself to some extent after cycling through heights multiple times.

If the systems is cycling in heights just fine, I'd suspect something else.

Ask them if they torqued the lower control arms with the full weight of the vehicle on the suspension. (LCA and sway bar)

I suspect, as many shops cheat and do, that they torque the suspension at full droop. This causes the bushings in the control arms to be pre-loaded at ride height. OEM suspensions use fixed and bonded rubber bushings that depend on deformation for suspension travel. So if it's torqued at full droop, it will be pre-loaded, and add to perceived spring rate. They might get away with this on normal cars, but our cruisers have massive suspension travel causing the bushings to really bind. This is also a great way to have them prematurely fail.

May also want to check tire pressures?

Pre-loading of bushings sounds plausible. Maybe more than trapped air, since the system itself seems to function.

Tire pressure checked and unchanged at 37psi.

Good inputs, thanks!

 

[Blekansikt]

Update. The dealer looked at this again, receiving input from this forum as well. They claim they have been bleeding again, and that the bushings had been torqued weight on wheel the first time. The car now feels good, and as I expected with a tiny difference between front and rear, and the difference is fading away. My theory is air trapped messsed up the algorythm, maybe combined with differences in viscosity front/rear due to old liquid in the rear and fresh up front. I'm not sure I believe this myself as I still tend to believe in the torque weight off wheel-theory. Anyway, now all good. AHC is good, really good. Holy crap, it defines the vehicle.