Is this a suspension issue? 500 Miles on new suspension and it's ROUGH.

If you look at the diagram I posted, the spring is compressed within a 10” area once the weight of the truck is on it, regardless of perch setting. The perch setting simply pulls the strut out longer with weight over it, resulting in lift - not by the coil, but by the length of the strut at rest. So with weight on it, there isn’t any more load on the coils at rest, whether you’re on the 1st perch or the 5th (or even when comparing to the stock strut/coil). The preload on a 5100 only comes into play when the shocks are extending to full droop, as the weight over them is reduced. At that point, the truck must overcome that initial preload to get back to its normal resting spot, where the coil then reaches the same “end compression”, regardless of perch setting.. But like I said earlier, that’s only a small fraction of the time that you’re driving. Most bumps/holes in the road don’t extend the shock close to full droop, so the ride quality within the typical range of motion of the strut will seem unchanged the vast majority of the time whatever perch you’re on.

 

Wut? I never said preload does not affect ride height. I said that it’s purpose is to adjust ride height. The controversy seems to be about whether different types of applying preload have differing effects on suspension behavior.

 

I don’t disagree with your explanation of preload.

 

I think we agree the load does not change depending on spring seat location, that would be the weight of the truck.

I think you are discounting that you are starting with different spring rates (due to preload) with the shock off the truck. 12" spring in a 11" space is not the same starting point as a 12" spring in a 10" space. The coil isn't getting longer, it is providing more resistance to the static weight of the truck because it is compressed. This is preload. How can you propose that the spring (with an increased preload, in this case) is not engaged? For that to be true, the shock would have to be supporting the weight, which it doesn't. And again, how can you explain people achieving more lift by swapping to higher rate springs without moving the seat?

 

Should've made it more clear I was in agreement with you

 

Preload has no effect on spring rate. Spring rate of a coil spring is based on material properties and geometry of the spring. Here is one explanation.

https://www.thespringstore.com/spring-rate-calculator.html

 

I'm with you, I was trying to reference it as a kind of "effective spring rate," since you are starting at a point further into the spring's compression. I see preload as a way to fine tune the spring's behavior within the material properties. So, rough example, you could preload a 600 lb spring to behave something like a 650 lb spring with much less preload (with other caveats, of course).

 

Preload is a way to adjust ride height; not much more. If kept within limits, it has only one side effect I’m aware of, and that is to increase the force the spring applies to the ground at full extension. If not kept within limits, it will result in the coils of the spring making contact, shuck will change the spring rate dramatically.

 

More resistance of the coil against the weight of the truck is what gives lift with higher rate springs, just like a spacer in the assembly does - the difference being that the spacer will not allow the coil to compress further nearly as much, making a higher rate coil a much better choice than an internal spacer. But with 5100s, the preload only compresses the spring a small fraction of what the weight of the truck does. Once the weight is over the suspension, that little bit of preload at assembly/with no weight over the strut is comparable to my 2 year old pushing a shopping cart with me… She makes literally zero difference unless we’re almost stopped then and only then can I feel her little push that might move the carts a few inches... much like how you’ll only notice the preload on a 5100 when it’s fully extended. After that, the thousands of lbs. of truck easily blows right past the relatively small bit of a preload from the coil. That beginning preload doesn’t matter any longer because at rest, the coil is squashed to the same exact size regardless of perch setting. Bilstien and every other adjustable shock manufacturer will tell you the same thing if you call and ask them. It’s science not opinion.

 

Like I’ve been saying, preload does not affect the spring rate. It only changes the ride height (disregarding the other effects to keep things simple). What are we arguing about?

I think you understand preload, but are over complicating it. It is a somewhat subtle concept. Conceptually the way I like to think about it is that it adds X force to the spring that needs to be overcome before the spring starts to compress. That effectively reduces the weight pushing down on the spring by X.

EDIT: it doesn't matter if you are preloading the spring from above (a preload spacer or a threaded collar) or below (a perch), the effect is the same. The spring is compressed at full extension of the coil over. The rest of the system doesn't know the difference.

 

If you understand that you need more force to further compress a spring, ie, 600lbs to go from 12" to 11", 650lbs to go from 11" to 10" (or whatever it may be), and so on, there is no way preload is not in effect at all times, from the get go. You are starting with a different "effective spring rate" before you ever put weight on it, which will obviously affect static height and ride. I have felt this after adjusting preload on motorcycles for decades. I don't think I can disprove your theory about moving the shock out of the bottom, but I don't think you realize you cannot eliminate preload from the equation. You are changing how the spring acts by starting it at a different point in it's compression.

 

Suspension coil springs can be modeled by Hookes law. Hookes law says that the spring rate is a constant. It’s the k in F = -kx. It’s not affected by the displacement of the the spring.

https://en.wikipedia.org/wiki/Hooke's_law

 

Preload is not what’s providing the lift with 5100s, it’s that the shock literally becomes longer at rest than the stock stock, the higher the perch setting you go. Look closely at the diagram I posted again. It’s about the best way to show people how the spring is compressed exactly the same under weight regardless of perch setting. I used to think it worked the way you do too, but eventually someone showed me this diagram and explained it in a way that it finally clicked with me and then it became obvious. It’s a complicated thing really. That’s why there’s so much confusion over it. The reality is, the shock just gets extended out longer, pushing the LCA down further, lifting the truck - The lift has absolutely nothing to do with the spring rate when it comes to a 5100. Lift coils do not lift the same way that 5100s do. Anyway, this debate is long and old and I’ve seen this convo dozens and dozens of times over the last 15 or 20 years that I’ve been on various Toyota and off road forums. There’s a reason there’s ALWAYS that faction of people like me pushing back on this. Because we know.

 

Don't get defensive. We're just discussing a simple but often misunderstood concept. At the worse we will both learn something.

What you are describing is the effect of preload. Preload causes the shock (more importantly, the coil over) to be longer at rest. it doesn't matter if you are preloading the spring from above (a preload spacer or a threaded collar) or below (a perch), the effect is the same. The spring is compressed at full extension of the coil over. The rest of the system doesn't know the difference.

whoa whoa... you said "Lift coils do not lift the same way that 5100s do". Did I miss when "lift coils" entered he discussion? You talked about preload spacers earlier. Changing spring length and/or spring rate is different than preload.

 

I think we are saying the same thing with different words. This graph from the same page sums up my point. I have probably been using "spring rate" incorrectly, though I understand it is a fixed material property. I'm trying to describe it in a practical sense, which I think this graph does.

 

I don't see how that diagram is applicable. Under normal circumstances, an automobile suspension spring operates well below its yield strength (in the range where Hooke's Law is a good approximation).

 

I recently was experiencing a similar shudder/vibration in my truck during acceleration, especially up any incline. It was a rougher vibration at lower speeds (20-35mph) and louder and higher frequency during freeway speeds (65+). I had a bad u-joint on my driveline, had all three rebuilt and replaced the carrier bearing out of precaution. The truck drives so much smoother, like new. Do you have any clunking sounds when you shift between P-R-D? I did, and that is another symptom. I’m at 130k though… good luck

 

I'm definitely not suggesting we go into plastic deformation. My position is that adding preload starts you at a higher "effective spring rate." Let's say you start with strain X and you need stress Y, to get there. Now add some preload and start with 2X strain. You need 2Y stress to get there given the linear relationship. To gain more strain (compression) while going down the road hitting bumps, you need more then 2Y stress to have any suspension compression. With our lesser preloaded example of stress Y, you still have the strain range X through 2X to move through, which is done with less than 2Y stress.

Point is just that it takes more force to compress a spring beyond a given point then it took to get to that point, but yes the relationship is constant/linear, but with preload added you are starting further down that road of needing more force for further compression. Rates always screw me up...meters per second, per second and all...

 

I think I might, def lurks forward some times when going into gear.

Just going to pay Toyota the 150 to either break my heart or make me happy. (Extremely expensive repair or reasonable… lol).

about 2k under 60k right now. So.. a little bit of a powertrain left.

 

Honest question regarding the 5100 perch/preload debate; if perch setting has absolutely no relation to ride quality, would a lift coil (OME 886 for example) work exactly the same on the 1st perch all the way up to the 5th perch? If not, why?