No, I pulled it out 20mm from the housing and did not touch the spring seats (had them at zero preload or just high enough the spring wasn't falling off the seats at full extension). Have not checked ride height at all, should be the same at the spring seat just 1in higher ride height.

Was calculating droop first (wheel hub to fender arch at full extension - at full compression to get shock travel, then divided by 3). All with no spring, but wheels on.

 

Good for you man. I have to go after widest tire first, get 5" springs...not sure where i'll end up ratio-wise
Thinking of making an isolator piece for the top hat

 

using your full travel measurement of 120mm then 40mm is the correct standard droop ratio yes.

Im wondering if youve got the full travel measurement wrong as its strange your overall travel measurement has increased. To set them properly from scratch you need to wind the shock body all the way down so its just off the top of the threads in the mounting point to the hub. then measure your full travel measurement. you then wind the shock body to the droop measurement which is full travel / 3. unless you have a minimum height requirement for a class you race in you can ignore the ride height for now. I do mine with the wheel off first by putting a jack under the lower arm and jacking the strut through its range till it bottoms out and starts lifting the car. Then check it again with the wheel on to check wheel clearance. if you need to wind the shock mount up for wheel clearance adjust the full travel and re measure once you have this. the closer you can be to the full shock travel range the better.

The shock body should then be set and forget and never changed again. you can then install your springs and you should then only do ride height changes via the spring perch offset. (moving the spring up and down). You can compress the spring to raise the ride height as long as it doesnt bind up the coils. and you can uncompress the spring so long as the spring stays captive when no load is on it. Remember if your using helper springs and your suspension does go into full droop the spring rate will effectively change during that time that the main spring has no load and the keeper is doing the work.

set the ride height via the spring perch and your all done

Heres a video showing the droop in red and the compression in green and winding the shock body up to meet the correct droop ratio. see how the piston and shaft dont move inside the shock body but it gains you more travel upwards for the piston inside the shock.

https://suspensionsecrets.co.uk/wp-c...der1-1.mp4?_=1

 

There are 3 primary ways to set up a shock body length, thats just 1. Typically what you would do with a softer spring rate.

 

Piston is 1/3 in. Why is it ideal to be there? Is there any mechanical or hydraulic behavior we need to be conscious about? Thanks

Honestly I can only imagine all this as 1) Piston 1/3 in AT RIDE HEIGHT (full weight of the car on suspension). 2) Ride height adjustment is now at the bottom threads so ratio wont be changed.
I know I'm missing something, I just couldn't figure it out. I'm checking out youtube vids

 

I kind of just take it for granted and havnt looked into it much. just did some quick research though and came across the following:

Basically it affects the effective travel range of the damper and makes it more likely to bottom out. It sounds like the bump stop etc is also calibrated with this length in mind and if you play with it you could push through the bump stop or be constantly on the bump stop

Copied this from an article from a guy who works for Eibach. ( full read here: https://www.motortrend.com/how-to/17...-gotten-wrong/ )Adjust ride height by way of those shock bases, though, and you could be headed for trouble. Jackson explains why he believes it's never a good idea: "You want to have droop travel and suspension travel; this is what keeps the tires planted on the road and gives you maximum grip," he says. "When you shorten the shock body, you're taking away precious suspension travel."

And it doesn't end there. "When you shorten shock body length, you're also increasing bump travel, which means the bumpstop now can't do its job properly," Jackson says. "This also means that the suspension can potentially bottom out on shock towers [and] wheelwells." According to Jackson, shorten that shock body enough and you'll also prematurely wear things out like ball joints, bushings, even CV joints.

"Eibach sets up [its] shock body lengths the same as [the] factory so we can retain the car's proper suspension travel and geometry," he explains. "Doing so allows us to pick the proper length and rate bumpstop to properly pair with each application."


There was also this from MCA which talks about setting up ride height: https://mcasuspension.com/technical/...ght-Adjustment

 

So the Eibach one doesnt care about compression-droop ratio, just as long as the piston never hit top or bottom while operating the car. OK Agreed thats the basic set up requirement.
My previous set up came with a foamy bump stop which only lasted about 5 years. I could be going past the bump stop mark in the earlier years when I had softer springs, but never hit the bottom though.
That MCA one is confusing to me. I agree you want droop and dont let customers adjust internal thread if it has no witness hole lol

Preload, this is not a thing. It theoretically becomes a thing only IF you've pre-compressed the spring more than the car's weight would while operating it. I dont think you can tighten the spring that much using spanner wrenches.
'Snug" is probably a better term, but I'm ESL lol
What confuses people, I think, is the statement "spring rate doesn't change". thats true but its a RATE in "lbs per inch". So with a 500lbs spring, you'll need a 500lbs corner weight to compress it 1 inch, 1000lbs to compress it 2 inches. If you've pre compressed the spring 1 inch then that 500lbs corner cant compress it further so you wont have any compression travel, so the suspension is harder (which feels like you replaced it with 1000lbs springs)

 

No, a linear spring rate is a linear spring rate. If you compress the spring 1" and then add 500lbs, it will still compress another inch. The 1" of preload is applying a static force of 500lbs on the spring with the threaded collar. If it took 1000lbs to compress the spring an extra inch after it had been been preloaded by 1" then you'd have a progressive spring rate. If the spring undergoes any amount of compression there is force acting on it, it doesn't just go away because there isn't a physical object on top of it compressing it.

This is why shop press accidents are so scary, you can't see or feel or hear press force until something lets go.

 

IMO, droop ratio is kind of a dumb way to setup a shock body length. Who cares where you are in the travel range, what you care about is where the ends are which in most cases is one end or the other is the point of concern. Either you have enough droop or you dont, either you have enough compression or you dont.

There isnt a single answer or approach that works for all because it just changed depending on a lot of variable like,

1. Is the car sprung high enough the static travel is smaller than desired droop
2. Is the body long enough or too long
3. Is there a hard part that's hit with excessive travel? What are the forces to get to that bad place
4. Is high aero grip > mechanical grip?
5. Is this track only or street use? Whats the ratio and how much is comfort a concern

Each one of these I can talk about a different need for spring, assist/tender, helper, and body length.

 

isn't that what I said? 500lbs for 1 inch PLUS another 500lbs for another 1 inch = 1000lbs for 2" of compression (from its original height)

 

The only way i'm seeing this as "not-dumb" and is-ideal is if its for how the whole car behaves WHILE RACING. That is probably from a guy with lots of experience and just kind of summarized a little too much. I can accept that

 

This is why i am imagining my droop is basically the compressibility range of my helper spring when mounted. I can make small adjustments later by the amount the main spring is compressing @ full standing weight

 

I think they do care about droop ratio, I think what hes saying is dont adjust it because its set by the factory already, Similar to what MCA are saying. keep the droop within 45 - 50mm as that is the desired droop ratio from the manufacturer. What hes trying to say is that if you wind the spring up too much putting the spring under tension it can effect the droop because you adjust the ride height of the car. Not enough droop and youll lift the inside tyre too early. This guy explains droop travel and spring pre load much better than i ever could:

winding "pre load" into your spring will also increase the static load and therefore as you said basically if you put 1" preload onto a 500lb spring anything under 500lb of force applied wont affect the spring. Therefore for example if you are oval or dirt oval racing you can use this to your advantage, you can play with spring preloads on softer springs to get the same benefit effect of running a heavy spring to get you into and through the center of the corner but also have the benefit of a lighter spring for more traction coming off the corner. For example, if you have a 500lb spring in the right rear of your car and it has 500lbs of weight on it, it should be compressed 1". If it travels another inch it will have 1000lbs on it. instead if you pre load and compress a 125lb spring 4 inches it will have 500lbs on it. If it travels another inch it now has 625lb on it, 375lbs less than a 500lb spring. Mainly on the right rear corner on a left hand oval.

We are really starting to go down the rabbit hole here and i cant really think of an application on a road course that would benefit from this. I guess if your getting into very technical stuff and you start measuring suspension travel via ride height sensors etc and want to tune per corner beyond just corner weighting the car then you would start to adjust droop ratios more to suit the track and application.

High level time attack cars will usually set their suspension up so that when the full aerodynamic force is acting apon the car the suspension is effectively sitting on a stack of bump stops which allows them to control the ride height and aero platform more accurately allowing them to run the car closer to the track surface and therefore increasing aerodynamics. or you could just go full blown electroncially controlled active damping aero like these guys did on RP968

 

Im not really sure im understanding what your saying but your helper spring wouldnt have any relation to shock droop. as soon as you put body weight onto the helper spring it will be fully compressed. they are literally dormant unless your strut goes into full extension and this would only occur in very rare scenarios e.g if you hit a big hole and the suspension fully extends or you lift a wheel. majority of the purpose of a helper spring is to keep the actual spring under load on full extension/ no load so it doesnt flop around and fall out of the perch. if you had the correct length springs for the ride height your wanting you shouldnt even really use keeper springs at all. they can be used to have a very very minor effect on going over sudden bumps etc where they can dampen the effect of them by effectively introducing a very small amount of low spring rate characteristics when the suspension goes into full travel/extension for a very short amount of time which can help with stability e.g if you were doing 400kmh and hit a bump in the road and the suspension maxed out it would be less harsh than if you just had a static rate spring in there.

 

I like this example. With a 500lbs spring you'd only get 1/4" compression from the additional 125lbs load, probably not ideal for that scenario