LR shock and spring setup

[Kromulous]

Yeah i was looking at the DEI Unit and you can adjust the nitrogen pressure, which affected the spring rate greatly. I made a little mount that i can add bisquits in, them nitro units are pricey.

Anyway, trying to wrap my head around with King1 is saying up there too, very interesting.

[fastford]

Running the LR stack without the lockout is kinda useless. Setting how much wheel load the lower spring holds at ride height is make or break the whole deal

now im confused , are you talking about a lock out like on a rt frt two stage ?

[MasterSbilt_Racer]

Might want to be a little more open minded to that lower spring load at ride height. Im all about dynamic wheel loads too, but that lockout location is 2/3 of the LR setup. You're only using the bottom spring until the LR drops out enough to come off the lockout and both springs are utilized.
But whatever, not here to argue about deck height, just trying to help the guy out.
Ask Mccreadie about how important that lower spring load is. If it wasnt then people wouldnt spend the money on a lockout nut.

It sounds like maybe you are saying this important point is above ride height now? This point you describe is important if the car reaches that height during racing conditions. Me, for what I need to get for load to hold the car up, and load at extension, there isn't much way to keep the stage nut in play for very long.

[racer2e]

Kent, I have been thinking about a position sensitive shock for the left rear front shock for some time. I built one years ago for a different application, but now I think you could have it with almost no damping except just before it tops out on rebound. My concern is how much it will change with bar changes. Maybe make a few of them with the port in different locations so the damping comes in at the same amount of total droop. To match a couple of bar positions you run.

[sidewinder69]

Billet can you offer more on the digressive and progressive concepts, I dont want any secrets . Just a general conversation to better enlighten

[billetbirdcage]

Kent, I have been thinking about a position sensitive shock for the left rear front shock for some time. I built one years ago for a different application, but now I think you could have it with almost no damping except just before it tops out on rebound. My concern is how much it will change with bar changes. Maybe make a few of them with the port in different locations so the damping comes in at the same amount of total droop. To match a couple of bar positions you run.

Simple, don't use the front of the birdcage for your hike down shock location. On top of the tube would allow you to use the same shock for all set ups. For some reason, you needed to change the drop or chain length just have the top mount on a screw jack. You could always keep the last 3/8 or 1/2" of the shock where the rebound goes high in the same place.

However again, back to is it worth anything? Shrugs

You can do a twin tube pretty cheap and yourself if you know how to take a shock apart. However if your wanting to do with a mono-tube, then you going to need someone to machine some stuff for you or know how to do it in other ways.

Hell, early in the 2017 racing year I drew up a position sensitive shock that at the last 1" of travel (fully compressed) it had 800# of rebound. So you just put the fat crew guy on the back of the car to smash it down and it would hold it there to go thru tech easy and once out on the track you just rock the car back and forth to get it over the high rebound and the car acted like normal just had 2" of static deck height. We all saw the writing on the wall but they eventually put the nose hieght rules that I said was needed before anyone understood it or why and what was happening. I just wasn't gonna explain it and lose the advantage that a lot of people didn't know was going on.

I guarantee I wasn't the only one that knew how to do it. Also the position sensitive stuff isn't new and been around on other corners of the car for a long time, just not many people will talk about it.

[hucktyson]

Make the right front static 10” max and check the deck height after the race on the scales like we always used to do .... That eliminates a TON of BS

[fastford]

billet , i read an article some where , i,m gone try to find it , that discussed a shock like your describing , i think they called it a variable shaft location valve or something like that.....

[Kromulous]

https://vimeo.com/103859987

https://www.youtube.com/watch?v=pyoYRSPmdwA

[billetbirdcage]

https://vimeo.com/103859987

https://www.youtube.com/watch?v=pyoYRSPmdwA

The problem with most of those bypass type shocks to make a position sensitive shock is they change both compression and rebound in those zones. So many of those styles can't just change comp or rebound without effecting the other also.

Now granted maybe you want both increased or decreased in certain places, but maybe you only want to change one direction and not both. Like I said, those been around a long long time. That style won't do what I was talking about, because you'd have high comp and rebound in that last part of the travel and less of both in the other 8" of stroke of the shock which wouldn't deal ideal in the situation I was describing as far as a LR front shock.

[billetbirdcage]

Billet can you offer more on the digressive and progressive concepts, I dont want any secrets . Just a general conversation to better enlighten

I can't say I got all the answers here as everyone seems to like different things. There are tons of ways to do a LR stack, personally I tend to not really look at them as progressive or digressive in a normal sense on their rate. I sort of have my own way at looking at them, which is sort of hard to explain but in my mind it makes it easier to make sense of it all and figure out what the car wants.

People get so caught up in certain things, but miss the big picture. This goes back to what I said in my first reply to you: That a single linear spring on the LR behind generally don't act linear at the wheel. With that being said, here are some things that can happen (I'm not going to overly explain or get into this very far)

Example:

Car A has a 87.5# rate spring (say a 175/175) and has 300# of extended load at full droop
Car B gas a 87.5# rate spring (say a 175/175) and has 200# of extended load at full droop
Car C gas a 87.5# rate spring (say a 175/175) and has 100# of extended load at full droop

I'm keeping the rate the same for simplicity, Typically if you change nothing on the car but just change the adjuster on the car to vary the open load from car A to car C and anything in between, you'd expect the car to stay up better with more open load. This is basically because there is more tension on the spring to over come for the car to fall. While this is generally correct, without taking into the progression/digression of the LR suspension on the spring rate the wheel sees it's possible for this to happen:

Car C even with the least amount of extended load could easily be the hardest to make the car set down.

So without taking all this into account you may not be accomplishing what your trying or making it harder on yourself.

[Kromulous]

I posted those videos just for reference purposes, so people can see the technology is out there at least. Application for a SLM would need to be worked on.

Interesting thou, i kind of like the idea of one of those on the RF. You could really use some of the added compression and the rebound of that style of shock when all the weight is over on the RF in corner entry. So essentially you could have a zero point of rebound way up and then ease off after that 1st 1 or 2 inches of travel.

[Kromulous]

Along the with the springs discussion.

A stack of a 275lb spring and a 125 lb spring yield a 86lb rate, close as i could get to Billets post.

Still thinking about King1's post, but I would think you could pre-load this to 100 lbs load at full extension that would require 1.45" of pre-load on the combo as a whole.

Now at ride hgt you have 675 lbs (18"), you could set the adjuster nut / lock out to engage and carry that weight, and that would require 2.45" of compression. So from full hike 24.5" to ride HGT is 18" (Just made up numbers) thats 6.5 inches of travel. You would engage the lock out about the last 1/3 of travel.

What i don't know, but will figure out is, will i lose the initial 100 lbs of load when the lock out engages?

Anyway, i would assume this set up would handle drastically different than a 200 / 150 stack, that correct?

King1 am i on the right track? LOL

[hucktyson]

I doubt you would feel the difference between a 275/125 and a 200/150 ..... if it’s a track where you stay in the fuel the entire time and the car stays fully hiked I really can see how anything but the open load comes into play. But even if not the rate difference between those 2 can’t be much

[sidewinder69]

Okay so your example implies the extension load doesnt matter because apparently the motion ratios or rotation effects more. Tell more