Help Debugging New Springs/Shocks Issue

[keylay31]

2007 4Runner SR5 4WD, 160k miles

Just had new shocks and springs put on this week after the original shocks were leaking. I did have a Cornfed 2/1 spacer kit on it originally as well which was installed when I first bought it new.

Shocks: Bilstein 5100 on 0" perch
Front Springs: Old Man Emu 2884 (590-lb / 15.3" Length 1.7")
Back Springs: Bilstein 36-281817 (1.0")

On pavement the new setup feels good (about as stiff as before with the spacer lift) but on concrete roads I'm bouncing up and down like an unloaded trailer. It's happening rhythmically between 40 and 65 mph, which of course is the speed of traffic on my main commute. I'm not sure if it's the shocks, springs, or combination of both that happen to be perfectly in sync with the spacing of the control joints. Almost feels like I need a mouth guard to drive on it.

Questions:

1. Could this be an installation issue?
2. Is this more likely to be the shocks, the springs, or the combination?
3. If it's the shocks, can I install new Toyota shocks and keep the current springs (can they handle the lifted springs)?
4. Any hope this will calm down with time as the springs settle? (It's still lifted more than 1.7"/1").

 

[4RunnerAquasport]

Might be improper install, but my First guess would be your rear springs may not be rated heavy enough.
Faulty shocks are not very common this early in their life cycle.
First thing would be to get it up on jack stands and do a visual to see if anything looks out of place. Good Luck!

 

[rdruss]

Bilsteins are definitely stiffer than stock shocks, especially worn out old shocks. I had Bil 4600 all around with FJ springs for several years and liked the ride for the most part, except over choppy road, they definitely give you feedback. I switched to Dobinson IMS shocks earlier this year and they are more compliant in all situations. I'm not suggesting you change shocks, but the Bils may take some getting used to and/or you may need to change springs. I'd drive it for awhile longer and see how it goes. Check your install as aquarunner suggested.

 

[Reinout]

Your old shocks might have had the same issues but were absorbing it. I'd check the balance on the wheels: they might be reverberating through the suspension harder now.

 

[keylay31]

The tires were inflated to 40, dropping them down to 34 took it from mouth guard level to just bumpy, thank God. No clue who inflated them that high, if it was the mechanic or the alignment guy. I’ll have to decide if I change shocks/springs but it’s much more manageable for now.

One other question, regarding the attached photo, is the lift ultimately too high, looking at the angle of the suspension? I don’t have the drop kit and didn’t upgrade the UCA’s. It’s been a month and I’ve had very little settling.

https://imgur.com/a/82Nu0Jc