Ass sag during acceleration

I’m having this strange issue where the front of the truck seems to get higher and the rear seems to get lower during acceleration. I see my headlights pointing higher during acceleration at night.

i have kings 600lb spring rate fronts set to 3.5” lift and unknown spring rate icons (158506) 2” lift on the rears.

im thinking the sag may be related to the icon springs. Perhaps the spring rate is too soft ? I’m thinking of switching to icon (52700). This seems to be the standard for icon 2” rear springs.

Any thoughts or recommendations will be appreciated.

 

I am new to the 4runner family, i have been driving tacomas for years and i was beginning to think this was a characteristic of the shorter wheelbase. Mine is lifted, I’m running toytec 2” standard weight coils in the rear, and spacers with the trd coilovers in the front. I am already panning a real front setup with UCSs, but was wondering if the rear springs were too soft and causing this feeling.

 

Are you hauling a lot of weight regularly?

I have Bilstein +400# coils and no such sag.

Being Icon, I wouldn't be surprised if the coils sprung a leak.

 

That’s what happens when you eliminate all the rack from the suspension...

 

I have gobi rack, sliders and ladder. Nothing else heavy on the truck.

 

so by leveling the truck .. this will cause the rear to sag during acceleration? Perhaps I can drop the front to 3” instead of 3.5”

 

I would second the rake thing. It's apples to oranges but a lot of drag cars and bikes have a significant rake in order to combat this. I kept the factory rake for aero (MPG's) and I don't notice the front end coming up on acceleration.

 

Yeah the rake thing make sense. But before I had the kings I had the trd pro Bilsteins w/Cornfed spacers. I was also leveled. But seems I have more sag during acceleration now with the kings/icons the Bilsteins. Both setups were both leveled. Other difference is

Bilsteins 23.25f/23.5r
Kings 23.5/24r

here’s the trd pro Bilsteins

 

Between the rack, ladder, and sliders, that's probably over 100# constant weight on the rear springs. If you're using springs designed for standard load, they might be a tad weak for your setup.

Also, it could be due to the Bilsteins having been digressive valved versus the Kings being Progressive. Progressive shocks will initially feel softer, so they may allow a bit more sag and roll than a digressive shock. This is just a guess, though

 

Those #600 springs in the front are new aren't they? They might settle a bit in the next few months. As @Thatbassguy pointed out, your rear springs might be a little under rated.

 

I didn’t realize digressive vs progressive made that much sag difference

 

Actually my kit came with 550 fronts and found used set of 600 and the rear icons 2” on IG. I wanted to try 600 first as I found a local set cheap.

my plan was to perhaps change to 650 once low pro winch is installed. So front and rear springs are already settled in.

i question. What’s the difference between 2” icon 158506 vs 52700. All the icon kits stages 1 thru 7 use 52700 as the rear 2” lift.

im wondering if 158506 is a softer rear spring but same height ? They look so different.



158506 (stock vs icon)


Icon 52700

 

I could be wrong. Don't ever discount the possibility that I am wrong.

I have read that progressive shocks can feel mushy, depending on the valving.

 

It's a combination of changing the suspension geometry from stock (leveled it out) which affects it's dynamic characteristics, as well as the change from digressive Bilsteins to progressive KINGS. Just like in side to side handling (body roll), the digressive Bilstein pistons resisted the front to back lean (body pitch) under acceleration and braking more, at least initially and under smaller loads, than the KINGS will. Personally, some pitch and roll is exactly what I'd want from a 3.5" lift.. feels more like a jacked up trophy truck that way, no? Isn't that the look / experience you're gong for?

 

I’m just trying to see if the sag can be improved. I don’t have confidence with my current rear icon springs 158506 as I can’t find much info on them. Also seems that the 52700 is the 2” the rear spring icon recommends.

 

Just touching on this since I had the same issue until today. I had front set at 2.5” and rear with icon 2” standard load rear springs. When I’d accelerate the ass would drop enough I could see my headlights come up and right into the rear view mirror of the person in front of me (cars). I had ome heavys installed in anticipation of the rear bumper and now the acceleration sag is gone. At least I can’t feel it like before. This was also happening since the day I installed the icons.

 

Which icon springs did you have ? Which ome did you get ?

 

Icon 2” standard load




And ome

 

Ohh ,, those are heavy load springs. You want to sell me your icon 52700

 

Also I know the first pic is going to be crappy. But here is a side by side comparison of configuration.

keep in mind in these pics I have dobinsons drawers in the rear but the issue happened even before the drawers.

 

I gave them to a kid at the shop that helped with the install.

 

If I has as much weight as you, I would consider stiffer 2.5-3” springs ..

thanks

 

Daytona, lots of taller spring options for the rears, if you aren't set on ICON. OME 895e, Dobinsons, and a "heavy load" Bilstein all come to mind. Also I think Wheeler's T12?

 

Yes .. I just didn’t want buy another 2” set without asking the experts