There are essentially two components which dictate the suspensions characteristics (aside from it's basic geometry)
1) Springs - determine how much the suspension will compress given a certain load. This load can be applied by adding weight or through weight transfer during acceleration (cornering, braking, accelerating). The stiffer the spring, the less the suspension will deflect given a certain load. This is why stiffer springs are needed when you start adding the steel bumpers, tire carriers, and gobi racks loaded down with all of your 'bro-verlanding' equipment. Stiffer springs will also make the suspension feel more tight over bumps.
2) Shocks - The effects of shock absorbers are more difficult to visualize than that of springs, but the basic summary is that it is their job to keep the tire in contact with the surface below by limiting (or controling) oscilaitons in the suspension. There would be a lot to cover here but sufficed to say, the shocks are the component with the largest impact in how the vehicle "rides". How smooth or rough it feels over uneven surfaces.
With that in mind, there are several reasons to upgrade suspension in the context of an offroad vehicle. Some lifts accomplish all of these goals, some only accomplish 1 or 2. Here are the main ones that come to my mind:
1) Increased clearance for larger tires
2) Increased suspension travel (more available traction over uneven terrain) ***Keep in mind that with an IFS like on the 4runner there is a limit to how much articulation can be achieved***
3) Improved traction at speed over certain terrain types (shock valving)
4) Increased load capacity
5) Improved aesthetics (let's not pretend this doesn't matter)
6) Improved approach, breakover, and departure angles.
7) Improved clearance for everything except the differentials
Here's how some common types of lift do in the above categories **my opinion**:
Spacer lifts:
1) Good enough
2) Terrible - spacer lifts decrease your downtravel by the ammount of the lift. This is the number one reason not to use spacers.
3) Terrible - limiting downtravel can cause the suspension to bottom out abruptly over uneven surfaces. Not good!
4) Neither help nor hinder
5) OK for leveling
6) OK
7) OK
Upgraded springs and shocks:
1) Good
2) Good as long as the shock absorber has enough travel
3) Good
4) Good, depending on springs. No adjustability though
5) Good
6) Good
7) Good
Coilovers:
1) Good - Great (adjustable)
2) Good
3) Good
4) Good - Great, again the adjustability allows you to dial in some spring preload to level out additional weight. As long as you keep it reasonable this should have minimal impact on ride quality
5) Good - Great (king coilovers are sexy!)
6) Good
7) Good
You are going to "feel" changes to your suspension in basically one of two ways:
1) You added a spacer lift, too short shocks, or topped out a set of coilovers which has limited your downtravel drastically, causing the ride to feel very abrupt and jarring as the bottoming out suspension rocks your vehicle like a shot over every pothole. You probably notice I reference downtravel a bunch, and the reason being is that lifts work by "pushing" the suspension more downward from its stock location. This isn't necissarily bad, up to a point, however if the shock absorbers aren't upgraded, you'll run out of stroke (then they become tubular limiting straps) or you may end up contacting the spring with the upper control arm, particularly if you kept the UCA stock (which will also mean you probably have the caster way out of alignment)
2) You have changed the shock absorbers in some meaningful way. This could be bad or good, depending on what you've done and how you're driving. If you're driving at high speeds in the desert and you just threw in some shocks valved to tackle such a job, you'll probably be amazed at the improvement over stock. If you selected shock absorbers designed to be paired with heavy duty springs for increased load capacity, but aren't carrying anything extra aside from groceries...then the ride quality will likely feel very rough.
As far as whether or not a suspension lift will improve offroad capability, the answer is yes, as long as you are not sacrificing the travel for the benefit of pure "height". Increased approach, breakover, and departure angles are all realized. Without getting larger tires, you aren't adding any ground clearance to the differentials, but your bumpers will be higher and less likely to drag in the mud or water or whatever you're driving through/over. The two largest improvements you can make to your 4runner for offroading are Suspension and Tires, and they go hand in hand. Both need to be chosen to suit your intended use.
Having typed all of that: I'm getting Fox 2.5 remote resi's and 285 Trail Grapplers, because I hate "settling" and because I f**king can :lol: