Okay thanks for the reply. The icons I have been looking are are obviously adjustable coilovers and advertise 2-3” of lift so what I was meaning by adding pre load was adding the max pre load they recommend. I’m not very educated on suspension but I understand that adding pre load will make ride stiffer but so will adding a stronger spring so what’s the benefit of the heavier spring? I have already sold the 0”-1.5” icons but from what you and another member have said is making me lean away from icon towards fox or maybe eibach. Would there be a issue with having rear icon 1.5” springs and their 2.0 shocks (digressive) and front foxes/eibach?
yes in a nutshell both will make the ride stiffer. however, with more preload you are just cranking more force onto the spring at ride height by compressing the springs. this makes the ride stiffer, but the small bumps and such will be more uncontrolled. maxing out preload can also reduce suspension travel as well, further reduce ride comfort. This also doesn't change the spring rate, so if the problem you are experiencing is due to heavier front ends and such (ie, in your original 1.5" coilovers) then the ride would suffer as well (being the spring rates are too light to handle the weight)
with heavier rated springs, it compensates for the heavier front end (ie, lighter 4th gen front vs heavier 5th gen front) so that you don't need that much preload. It can make the ride stiffer, but that is because more weight is required to compress the springs.
In a more extreme scenario, see the following videos:
This is with the stock Fox 2.5 DSC springs. Notice how I called out "bottomed out" when I land after hitting a relatively small bump.
This is with the 700lb front springs that I swapped. Notice how the terrain is even more bumpy, but the truck didn't reflect that bumpiness in the cab. This is due to heavier rated springs doing work and pushing the shocks to decompress, and the Fox's valving, along with the adjustment knobs, control the compression of the shocks to reduce bumpiness.
So, adding more preload is more like a band-aide solution that doesn't really cost money while swapping springs is more of an optimal way to approach.
Another example:
I've cranked up preload on the kings on my 4Runner before, after adding front bumper and skid plates. Still bottomed out a lot.
Swapped over to heaver springs after a few runs and reset the preload to correct amount, and all was good. No more bottoming out.
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would it be fine with rear icon and front fox/ eibach? yes it would be fine for the time being.
If you run it hard like I do, then that wouldn't be ideal due to different valving and performance.
so... it's entirely up to you if you wanna swpa the rears too.
ps: the rears utilize the pin top design.