I love the stock suspension other than nose dive for a daily driver. I was debating on a 2-2.5 spacer on the front so I didn't lose the ride. But instead, if I went with the 5100s all around, does the ride quality suffer?

I found it improved noticeably. Not harsh, but firmer. Better feedback from the road, or maybe me imagination.

I've done 5100s on two 5th Gens, an Sr5 and a TE. The SR5 needed it and benefited the most (in my opinion).

Ditto......although I went with Bilstein HD series. Great ride, not rougher, but more controllable.

With the 5100's you have more slow-speed damping and less high speed damping.

Translation: Bumps are soaked up better, and the whole thing doesn't get out of sorts on a wavy highway or nose dive the way it did before.

Plus the shocks have longer stroke than stock, which prevents the head-toss effect when the suspension tops out (like empty vehicle, just one driver).

All in all, it feels like it should have felt coming from the factory - more stable, and much less fatiguing to drive.

What the difference between HD and 5100? Also, Im reading that once you add leveling spacers you may need longer springs?

I know typically springs control ride quality...but always best to ask! Thanks guys.

I had mine done at middle (2nd position) a few months ago. Front shocks only. That leveled it out and got rid of the rake. I think it rides better (firmer) with reduced nose dive. I had mine installed at my Toyota store. I just drove it for the first time at night last night on a 4-1/2 hour dirve in the rain. I had asked the accessory manager to ask the installer to check the headlights in addition to the realignment. Evidently the headlights were not readjusted. I had a number of oncoming drivers flash at me even though I had my fog lights on as well to let people know I was not running on high beam. Low beam was somewhere between normal high and low. On low beam the big diamond shaped signs had some of that glare back you get on high beam-just not quite as much. Those small reflectors placed around curves were brighter than normal as well. Since I don't know where to place marks on my garage door to properly adjust I will have the dealer to what I asked them to do in the first place.

If you get the adjustable front shocks and change the level of the vehicle, make certain you get your headlights readjusted in addition to the realignment. I was surprised how bad the illumination is. High beams were useless and low beams were weird being positioned between the proper low and high beam.

Spoke with rep and he said the damping rates for the HD's and the 5100 series were the same. Only difference is in the adjustments on the fronts of the 5100's and length of shocks for lifts. My HD's are same size as originals, and as such have no adjustments..

There are a lot of claims for the 5100 shocks, and I would like to explain two (what I would call) misconceptions. If you see any mistakes or have any questions, please tell me.

1. Preload

People say when you increase the perch setting you are "preloading" the springs. I don't know if the term preload is just thrown around, but regardless it is the wrong term when it is usually used.

A spring is defined by Hooke’s Law:

F= -kx

This means that with a force (F) and constant spring rate (k) a spring will always compress the same amount (x). When you adjust the perch setting on the shock, you are not changing the spring rate or the total force applied, so the spring will always compress the same amount -- moving the perch only changes the position of the spring seat (making the truck taller or lower), not the "preload" on the spring.

2. Perch Harshness

People claim that at higher perch settings the ride is harsher. We've established that the spring rate doesn’t change as the perch setting moves.

The 5100 is a viscous damper meaning its damping is velocity dependent and not position dependent. In that regard, perch setting shouldn't modify the harshness because the velocity of the shock isn’t dependent on perch height.

My assumption of people saying they feel a harsher ride is a result of new shocks, springs, the truck sitting taller, sway bars effective stiffness, etc.

So spring rates are a linear expression. Do you think that the limiting factor is the amount the coil can compress? Do you think ride quality will suffer by raising the spring seat of a Billy 5100 to 2.5"?

I've had 5100s front and rear in my 4th gen for 6 yrs, being the front adjusted to 1.75 on stock coils all around. It is the most practical setup out there if you are going for the leveled look and at the same time minimize the nose dive while braking, and it rides great definitely stiffer than stock. Once I asked myself if I would like to go back to the marsmallowy ride, and hell no.

I put the HDs on the rear before and that was stiff, Really uncomfortable when going through speed bumps unless its warmed up. I replaced the HDs with 5100s after 2 yrs. What tempted me with the HDs was the price about $50-60 at that time. They are also at stock length and can be use only with stock springs.

Keep in mind that its the rear setup that dictates the ride comfort, whatever you installed in the rear causes most of the trouble.

The post you responded to is over 4 years old -- sad to see that efforts to stamp out the "preload" myth were ignored 4 years ago just as they are today.

As you increase the amount of suspension lift, you lose some ride plushness because of changes to the suspension geometry. A bit more of a vertical force component is translated to the frame, which results in greater impact harshness. This would occur even if the spring rate and shock valving aren't changed. So yes, all else being equal, a 2.5" lift will ride somewhat rougher than stock -- whether it's enough to be objectionable is up to individual taste.

Raising the spring perch position limits droop travel because the suspension is extended farther in its resting position (and thus, the vehicle sits higher -- that's why it's called a "lift"). The amount that the spring is compressed under the weight of the truck remains the same.

What snivilous said (in a vacuum) is somewhat true but doesn’t read right to me (and this is obviously a super old post). He’s right in that the spring rate won’t change on linear coils, but the force exerted (by the spring) absolutely changes with compression (x). What snivilous said is accurate after spring force exceeds corner weight of your 4Runner. Before that, moving the perch changes x in the equation, which is why the vehicle sits taller, first because of spring force (more force pushing up), then because of general displacement (because corner weight is exceeded by the spring). This is all assuming a static condition. There are way more things gong on while driving down the highway.

The way to adjust height without changing the force a ton is to first choose the appropriate coils for your use case (do they need to be the same spring rate and longer, or maybe the same length but a higher spring rate?). Then to choose the right spec for your shock (length, dampening force, etc). I believe 2.5 is the max height of 5100s for 4Runners. The ride quality would be affected for a few reasons: less shock travel available and more preload (i.e. the coils require more force to compress further or they will push to their neutral length with more force; like driving over a pothole).

OA

Sounds like I’m way off base now - are we saying changing the perch doesn’t compress the spring any more than the stock condition? Essentially the spring force is at or exceeding corner weight off the bat?

I may be looking at this from too micro a level (if I’m wrong that’s fine), but the idea of that seems absurd considering the stock spring rate should be in the 600 to 700 lb/in range.

OA

No worries, it's a very common misconception. The easiest way to reconcile it is to forget for a moment about the coilover assembly process (which does indeed involve "preloading" the spring to fit it in under the coilover hat). Just imagine that the T4R had a traditional suspension with the coil separate from the shock. Moving the spring perch up and down simply changes the position of the spring relative to the vehicle frame, thus causing the truck to sit higher or lower. It doesn't change the amount that the spring is compressed, or the amount of force with which the spring is "pushing against" the spring perch.

Yes, the truck's weight on the spring far exceeds the amount of compression necessary to assemble it into the coilover, no matter how high of a spring perch position is used. If it didn't, the coilover would be rattling around loose in there (if it weren't bolted down, that is).

Hope this helps.