Alabama thread!

Shaft is fully extended when off of the truck and allows the spring to be compressed by the adjustment nut.

take that same coil over, put it on the trucks weight, shaft moves up, adjust the collar while on trucks weight, coil length doesn’t change or compress but the shaft moves back out. Weight is constant.

 

Ok do that measure the spring on the CO before you put it on the truck. Make those adjustments take CO off and measure spring you compressed. Trust me do it and you'll see.

 

It’ll no doubt be compressed that way. You’ve changed the weight

 

measure coil length with truck on its own weight.

adjust collar down 1/2” on or off truck

put truck back own it’s own weight and measure coil

the two coil measurements will be equal.

the dilemma is running out of down travel and coils slapping before the shock bottoms out

@ovrlndkull I think we are talking about the same thing but different on initial and final spring lengths. Im envisioning this adjustment happening on the truck in real time. You pull that coil over off after making an adjustment and yeah the coil length will have changed.

Im not being an ass and it bothers me very little to be wrong, I genuinely just want to know more about all this. Im not trying to attack you or anything like that, this is just a scholarly debate for me.

 

That's not entirely accurate. That also goes back to my first statement on how linear rate springs work. Like I said you have to understand that to understand preload.

So lets take your example for arguments sake but for ease of explanation we'll use even inches of travel and a 600# spring rate, ok.

So 0 preload IE the spring is not compressed at all with no load on them lower truck down onto spring now the spring measure 2" shorter than it's static length. Now add 1" of preload by adjusting that collar put weight of vehicle down the vehicle drops the spring an additional 1" now the spring is once again 2" shorter than it was at static length. So the 1" of compression took 600 compound to 2" that's 1200# to get that 2" shorter than static ride height.

Now go cranking down on that spring so you have 4" of preload, or 4" shorter than static length, lower vehicle since 4" is 2400# and the vehicle only had the weight to compress 2" or 1200# that coil will still be 4" shorter.

So yes there is the potential for the spring to end up the same height depending on spring rate and preload there is also the potential for it to end up shorter still.

Do what I've been telling you and you'll see what you are adjusting isn't the spring in relation to shock body and length of shock but preload of spring.

 

I get what you’re trying to say, I’m saying at ride height after making an adjustment the coil length won’t change since no weight has changed. Take it off the truck and the coil would be shorter than before you adjusted it since it’s resting on the shaft that’s bottomed out

 

Like I just showed depends how much you adjust and add preload. You can adjust and add so much preload it's shorter than when you started and would be the same with vehicle weight or not.

All of which goes back to you're adding preload.

Now start where you wanted measure spring unloaded then make adjustments to get it where you want it and measure spring unloaded again it'll be shorter the second time again doing what I've been trying to tell you happens adding preload.

Just do it and you'll see.

 

We are on the same page haha I think we were just thinking about the shock at different points and getting confused. Adjusting the collar will always affect coil length measured when off the truck (unless backed all the way off or something) and no weight. With weight added, spring compresses and the shaft being free to move in the shock body and not fully extended allows the spring to keep an equal and opposite reaction to the truck’s weight and it’s length will be constant when measured at this time, independent of moderate changes to the collar.

 

But it doesn't have an equal.and opposite reaction. If it weren't preloaded that would be true. Since you are ALWAYS adjusting preload with the upper spring perch you are ALWAYS changing the the potential energy of the spring when adjusting it. Minute changes may appear to be just moving the shaft outwards or inwards but in TRUTH you are changing the stored energy. Compressing the spring or preloading increases this stored energy and compounds the weight in which is required to compress the spring more from that point. Decreasing preload does the opposite. In theory what you are saying is true in reality it is totally bunk and you can see that by doing what I said eliminating the trucks weight on the spring and seeing the difference in preload when not under load. That's the truth of the matter.

Ok great example what NASCAR calls wedge, all they are doing at the pit stop is making minor adjustments to the upper spring perch either adding or subtracting preload. This is the exact same thing as the coilovers, has nothing to do with ride height that's just a side effect of increasing or decreasing the stored energy of the spring. These minute changes actually equal to big changes dynamically on the track.

This is why that explanation and diorama that accutune made is totally disingenuous and completely incorrect. It can affect ride quality, handling, and shock performance. I'm never going to recc them again after seeing that.

 

It compresses at a linear rate. If you preload the shock you are preloading at a linear rate (it takes the same force to compress it one inch by turning the collar as it would weight of the truck, weight is a measure of force). It’s not an exponential function in a linear spring. Put the vehicle back on the ground and it compresses further at the same rate (unless coils touch) Instead of compressing the coil more past what it would do with no preload it will “push” the vehicle up higher granted that it is not at the end of the shock’s stroke.

the measurement of the coil im referring to being the same is with the trucks weight on the ground. Adjusting the collar down will have the same effect on coil length as dropping the entire assembly like with a spacer lift (all shaft position and travel concerns aside)

 

Quit making me dust off the statics and dynamics book, my brain can’t take it

 

You are starting to be on the right track. Linear in fucntion but compounding. 600# spring. 1" requires 600 2" 1200 and so on. So if you preload it say 4" you are essentially at what 2400# would compress it. Now lets say the vehicle only compressed it 1/2" more that means it put 2700#s of force onto it.

Now think of a preloaded or precompressed spring vs one that is not. The preloaded or precompressed one has X amount of stored energy trying to expand where X= spring rate(#of inches of compression). This is why when you add preload it increases the ride height.

You precompress the spring to whatever point so to go past that point the vehicle has to overcome that stored energy/compounded rate to compress the spring more from that point.

It doesn't push the vehicle up it adds to the compounded linear rate which for lack of a better explanation stiffens it and makes the force needed to compress the spring that much greater.

It's hard to understand that because of the way springs are sold and labeled. If they were labeled as 600# compounding linear rate spring it'd be easier to wrap your head around it.

If a 600#spring literally only took 600#s then it wouldn't even hold the trucks up because it would fully compress. Thats why they are compounding.



There is an equation to figure out what spring rate you need and it's based off a 100# spring. You set your CO with 0 preload. Then lower the vehicle and measure the compression. Then you take the (# of inches of compression)100# that gets the rough corner weight of the vehicle. You then take that information and apply it to spring rates.

Example: Lets say that vehicle compressed the 100# spring 12"
100(12)=1200

Rough corner weight of the vehicle is 1200 lbs. Now you can take this information and apply it to spring rates this is where all of what I have been preaching comes together.

So we'll choose 3 different springs for this vehicle a 600, 800, and 1200 lb spring.

Starting with 0 preload
600# 2"
800# 1.5"
1200# 0
At 0 preload the 1200# spring will be max height 800#1.5" lower and the 600# 2"

To get them all the same ride height starting with getting the lower rate springs to the same ride height as the heavy spring.
600(2)=1200
800(1.5)=1200
1200 neutral
Setting that preload allows them to be at the same height as the heavy spring

Now lets do the opposite we want to get all the springs to the lowest ride height of the 600# spring. This is assuming we have enough room on the CO to allow for full extension and the springs to not contact upper or lower perches.
600#0 preload upper perch just touching off on the spring.
800# spring perch .5" off of spring
1200# spring 2" off from spring this will settle all to the lower ride height.
(This scenario can also be used to show the necessity of choosing the right spring length, that's a different conversation)

Now lets get the vehicle to what the ride hieght would be for the 800# spring upper perch just touching the spring.
600# spring would need ~.67" of preload
800# 0
1200# .5" upper perch away from the spring.

You're brain is hurting because you are using the complicated engineering physics equation VS the simplified redneck figured this shit out running shine equation.

That equation is essentially saying the same thing I've been pounding on. I've just been using easy #s and a simplified equation. That takes the long route of using a comparison of static length vs compressed or expaned length. If you just take your spring rate and multiply that by how far you want it compressed you get the same answer just simplified.

Your equation lets say we end up with a 600# spring that's 14" and you want to compress it to 12". F=(600)(14-12); F=600(2)=1200# of force to compress 2" now to go the next 1" your equation F=(600)(14-11)=1800lbs

This is why I say it's compounding linear, a much better term.

I am doing this equation in my head about 2x faster than the long winded way in which they show application. Real world you know your static spring height and then you just measure your preloaded height and then multiply rate by the difference.

This all circles back to me telling you to make those adjustments take it off the truck and remeasure you'll have a difference in preload thus a difference in the compounded linear stored energy of the compressed spring thus a potentiality of harsher, stiffer, rougher, less controlled ride.

Which all this circles back to spring rates and the compounded stored energy and the amount it takes for the next bit of travel and it's affect on valving.

Take your 700# spring vs the 650# spring. For the same ride height the 650 has to be preloaded more as shown above by maths. Now truck is same ride height valving in shock is the same both springs. To compress or rebound the 700# spring has more potential energy than the 650 in it's next 1" of travel which with the wrong valving can make the oscillations of the spring be uncomfortable. But the 650 may be better suited to that valving as well feel softer because it doesn't take as much force to compress that next 1". Now at the same ride height they both have the same potential energy stored for expansion. Now if we took them and preloaded them equally the 700# spring would feel harsher upon expansion because it has more stored energy.

 

TLDR Cliffs notes
You're on the right track just forget everything that accutune has stated and start applying. They misrepresented everything and have you confused but now you are starting to get it.

 

Good god just finished packing up the truck and you guys have written a novel about spring rates and preload I think I know everything there is about it now

 

That’s just the spill over from basic physics. Let’s assume a static system, because getting into the differences in spring rates in a dynamic system is going to get convoluted real quick. In a static system (parked car) the sum of all forces must equal zero. The force from weight (a function of mass and the gravitational constant) pushes down- ground pushes back with an equal and opposite force. The spring is sandwiched between and compressed based on a function of force, length and the spring constant. Those forces must equal zero. Adjusting the collar on my coil over will push down on the coil and it’s equal and opposite reaction will be to raise the truck since the threaded body and frame etc. are one system and coil, lower mount and tire/ground etc. are a “separate” system. This is only possible since the shaft can move freely within the shock body (static, so no dampening taken into consideration). If the shaft was fully extended at ride height for some terrible reason, the equal and opposite force would be on the shaft end.

It’s pounds per inch and means exactly that- how many pounds to compress the spring one inch and doesn’t matter how many inches have already been compressed, it’ll take the same X amount of pounds more to compress it another one inch. Compounding is a nonlinear (exponential) relationship like compounding interest on a loan. A linear function will not compound. It’s a slope, not a curve.

Your math looks right but I’m not sure I follow you on the potential energy. That’s kind of a whole other thing involving work in this case but here it is if this helps-valving is another dynamic goodie we shouldn’t consider for this case. Raising the height will effect the truck’s moment of inertia amongst other things and that’s an even bigger can of worms I’m no where near comfortable tackling these days.

When I get the chance I’ll take some pics and measure what I’m referencing, it’s really simple, and you’ll probably end up saying yeah that’s what I was saying dumbass and in the end who cares let’s go ride on our whatever the hell coils and valving hahaha

 

Well this is a cluster....lol

 

The dude at filthy motor sports (who did craw pedia) knows what’s up

 

A compressed or stretched spring has stored energy to return back to it's original form that is in the from of the equation which you posted again a little more complicated than needs to be. A spring with no compression at rest in a static state has a potential for energy but is not under any tension to do such.

I know my math is right because I've been doing this for near on 25 yrs when I started racing the roundy round stuff but we were old school rednecking it. Just never knew the formal physics and engineering stuff until 10 yrs later.

I use the term compounding so that it's easier to wrap your head around too many people think opposite due to the wording used in advertising springs
so 600# spring =600 for 1", 1200 for 2", 1800 for 3" and so on. But you are correct it is in a linear fashion and graphed it'll look like you say. Some people have a hard time wrapping their brain around that so I change the terms because the light bulb usually goes off and they get a better understanding.

Yes cranking down on the collar raises the truck due to the equal and opposite reaction. But what you aren't understanding is that equal and opposite reaction if taken off the truck and measured after the adjustment is made is either adding preload or taking it away to increase the weight needed to press the spring down at the next incriment or lessen that weight needed to compress it. It simply doesn't just move the body of the shock around the spring perches. That equal and opposite reaction is always on the shaft end as that's where the lower coil bucket is. THIS is 1000% how it works do the experiment as I told you and you'll see. The shaft doesn't move freely it is in direct connection to the spring via the lower and upper spring perches. So cranking down or up increases or decreases spring preload which increases or decreases ride height that is the true and correct answer and not what AccuTune stated.

Yep best source I've found thus far which is why I linked and have said to go there many a times.

 

I believe the picture from Accutune to be accurate. Whether it uses the term preload in the correct way- I don’t know. Judging by their free body diagram that is a static system in equilibrium. I believe their results can be easily replicated and when I’m doing the jd kit I’ll do my own experiment and report back.

You’re on the right track, but when the coil is preloaded that is subtracting from what the vehicle’s weight needs to do to compress it

let’s say five turns equals half an inch on the thread body and with a 600#/in coil that would be equivalent to having a truck 300#s lighter. But the truck won’t change weight, the 300# comes in the form of not compressing the spring more- that is what will keep the coil length measurements the same at ride height both before and after adjustment while on the truck. The shaft has a range of motion when the spring is compressed by the trucks weight only. When off the truck the shaft is fully extended.

if I were to adjust the collar with the truck on the ground the coil length wouldn’t change while I’m doing it since it’s being compressed by the trucks weight enough for the shaft to move. However, when taken off the truck and the shaft is allowed to fully extend there would be a difference in coil length measurable by how many turns you made

the Accutune picture is correct and clear enough for everyone to understand so I’ll leave it at that.

 

Dude I've been right this whole time you're the one believing something that is completely bunk and doesn't understand what preload is how it's measured when it's measured or how a CO of this design really works.

Highlighted part is kinda correct.

Coil length won't change while adjusting on the truck until you reach the preload point of the trucks corner weight then it'll start getting shorter. Proven by the maths and the equations YOU posted and I have been using this whole time in which I used to prove, I can also prove this in person.

I'm telling you this isn't how any of it works and you're completely off base AccuTune is wrong in saying that adjusting the collar just moves the shock body to adjust ride height.

AccuTune's picture is not correct because it has you believing the shock body moves separately from preload and doesn't affect any of that. Why does it matter because it is false information that the masses like yourself have gobbled up as truth in reality it is incorrect. It appears to do what they are saying because you never take the CO off to check your before and after preload measurements. Cranking down on the collar no matter what way you slice it shortens the distance between the upper perch (collar) and lower perch on the shaft. This increases preload which is measured unloaded. Which again circles back to the equations and then what it takes to compress to the next point. Like if a 600# spring is preloaded to 2" to compress it another in it'll take total 1800#s of corner weight but if your truck only has 1100 lbs of corner weight it won't compress it anymore at all. This goes back to the way I mentioned about getting corner weights.

Again you have to understand how it all works in relation to figure it all out.