LR shock and spring setup

[n4cgrt]

What are guys running on the lr of a blue gray rocket. I heard some guys trying a longer and softer spring any truth to that? What length and spring rate? What are the pro vs cons

[CCHIEF]

80-125# Barrel Spring, car bars up without having to "whip" it up on to the bars. ...Doesn't play nice with short LR upper bar.

[Punisher88]

Some are also running the big 5" 50 pound swift spring.

[CCHIEF]

A call to Rocket Parts Dept will get you on the right stuff.

[Kromulous]

A 50 lb spring? wow thats crazy.

I seen some guys with a spring with a large end on it, one side was normal, the other was 5" thought it must be a really light rate.

[MasterSbilt_Racer]

A 50 lb spring? wow thats crazy.

I seen some guys with a spring with a large end on it, one side was normal, the other was 5" thought it must be a really light rate.
I been using a 75# effective rate for years.

[Twenty-Five]

What effect does the type of limiter chain cushion have when your on a super soft lr spring? Rubber vs a spring ect.

[RaceEngineer]

What effect does the type of limiter chain cushion have when your on a super soft lr spring? Rubber vs a spring ect.Regardless of LR spring, you need travel to be consistent, you need momentary tire slip to not cause a large change in vertical wheel location, and you need some kind of cushion at all times. Many ways to get there.

[fastford]

I been using a 75# effective rate for years.

your talking stacked , not single right?

[fastford]

Regardless of LR spring, you need travel to be consistent, you need momentary tire slip to not cause a large change in vertical wheel location, and you need some kind of cushion at all times. Many ways to get there.

you are correct RE , i like my home made stop on my under slung frame and no chain pretty well.....

[MasterSbilt_Racer]

your talking stacked , not single right?

Correct. But all the divider does is help with bowing over a single spring.

[Twenty-Five]

Regardless of LR spring, you need travel to be consistent, you need momentary tire slip to not cause a large change in vertical wheel location, and you need some kind of cushion at all times. Many ways to get there.So how do we go about determining if we have the right cushion? Ideally something that gets close to but never bottoms out ie. coilbound??

[hucktyson]

RE is right if it goes up easy it also comes down easy .... even from a momentary tire slip .... unless you do something to stop it

[CCHIEF]

And now you know why shocks..and driver are so important now days

[billetbirdcage]

What effect does the type of limiter chain cushion have when your on a super soft lr spring? Rubber vs a spring ect.

I'm going to take some liberties here to make this simpler: Lets say that only the traction of the LR tire and it's force on the bars is what is making the car hike and hit the limiter.

So if you induce some wheel spin then you lose some of that force to the bars and the car may drop some, but if you have a cushion on the chain that was compressed some then it is also going to pull the car down (effectively shortening the chain).

Say that the chain cushion was compressed .25" and to do so was a force of 250#, so if you induced wheel spin and lose 250# of force it would uncompress the cushion that .25" and make car drop.

With all that said (again liberties being used): There is an inherent difference in how things rebound. Lets say that cushion was something like memory foam (like bed material), where you press down with your hand and if you remove it quickly you still see a dent in the material and can remove your hand away from it with out it pushing your hand back. Now granted if you move your hand slow enough, the material will push back on you hand but only if you do it slow enough.

It's travel over time or distance over time, that has to be considered. Take a steel spring, it rebounds so fast that it's pretty much impossible to move you hand fast enough to not have the spring touch or push on you hand. So if I move my hand at 100" per second, then the spring will always be pushing on my hand in a rebound matter. However something like a rubber/foam/etc, may only rebound at 10" per second so if I move my hand at that speed or faster then there really isn't any force on my hand pushing it up.

So, you can see that if you have a material that rebounds at a slow rate then it will have a tendency to not pull the car down as easy if I only break traction for a .1 of a second as it doesn't have enough time to rebound the whole amount to uncompress the cushion the whole amount it was compressed.

Example: fictitious but say the same rates and compression amount for both types of cushions just a different rebound rate of distance vs time. Both compressed .25" and 250# to get it there.


Steel spring rebounds at 100" per second so that rebounds .25" in .0025 secs

Memory foam rebounds at 10" per second so that rebounds that .25" in .025 seconds

So if you lose traction and lose 250# of force on the bars for .01 seconds, then the spring will pull the car down the full .25" but if you have the memory foam, then it will only come down a small % of that say like 30% for a travel of .075".

Hopefully that is simple enough that it makes sense.

[sidewinder69]

my real question is why would you want progressive or digressive left rears,,, i understand pro uses the bottom spring to set ride height, and top coilover is setting the extension load.... while digressive it is opposite. but still can arrive at same point. so what is the difference?? and how do you know the extension load you need to be at for a condition

[fastford]

billet , do you think the load applied to the rubber on a chain is equal , load wise , to the rear hitting the rubber on my under slung ? just wandering because this might be where something could be learned with a spring smasher and some rubber......

[hucktyson]

It would depend how much contact area you have on each. For instance you the rubber piece was 2.5” with a 2.5” steel washer trying to compress it the rate would be much stiffer and if a rib from you side bell was trying to crush the same
Piece of rubber. But if you had the same
Surface area it would be the same either way

[billetbirdcage]

billet , do you think the load applied to the rubber on a chain is equal , load wise , to the rear hitting the rubber on my under slung ? just wandering because this might be where something could be learned with a spring smasher and some rubber......

Load is load, so if you got a similar rate and travel/time then yes on a chain or under the rear end would be the same. However like Huck said, it would need to be tested and adjusted to get them actually the same if you knew one that worked perfect.

To be clear, I wasn't saying one is better then the other but they are different and you can get some, a lot, or almost no noticeable change felt on the cars.

Just because I tried explaining something, doesn't mean I actually know what is best. (grins and shrugs)

[Twenty-Five]

Load is load, so if you got a similar rate and travel/time then yes on a chain or under the rear end would be the same. However like Huck said, it would need to be tested and adjusted to get them actually the same if you knew one that worked perfect.To be clear, I wasn't saying one is better then the other but they are different and you can get some, a lot, or almost no noticeable change felt on the cars.Just because I tried explaining something, doesn't mean I actually know what is best. (grins and shrugs)Thanks for the great response billet! Given the fact that theres a ton of options for limiters available today, how would you go about picking one and then what sort of tendencies would you expect it to exhibit on the track when it's tuned properly? In other words if you watch a video of the limiter on the car what would you want to see?

[Kromulous]

Recently been looking into nitrogen type limiters, it seems they have the ability to add in quite a bit more progressive rate than rubber, or some sort of poly / foam type pucks. Anyone running the nitrogen types?

I guess the next question is, what kind of rate are we wanting on the limiting device?

[fastford]

i saw a home made chain limiter that he used a cone style bump stop , think it was yellow , that worked well and was compact . this is what i was gone try but because we run under slung frame , i went that way.....

[King1]

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

[manwplan]

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

How the car rides through the pits is irrelevant hence the current deck height and nose height rules. It's all about dynamic loads

[MasterSbilt_Racer]

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

I don't race at ride height. If you want to put a stop on there or something, have at it.

[King1]

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.

[billetbirdcage]

my real question is why would you want progressive or digressive left rears,,, i understand pro uses the bottom spring to set ride height, and top coilover is setting the extension load.... while digressive it is opposite. but still can arrive at same point. so what is the difference?? and how do you know the extension load you need to be at for a condition

You do realize that the rate the LR see's even with a single linear spring isn't linear? While it can be, typically it isn't on most cars.

[billetbirdcage]

billet , do you think the load applied to the rubber on a chain is equal , load wise , to the rear hitting the rubber on my under slung ? just wandering because this might be where something could be learned with a spring smasher and some rubber......

Forgot last night to say this:

Keep in mind you can get the bottom deal to be just like a chain but there are some inherient issues you have to over come.

1. Some cars will hit the undersling in the bell area, where the rear end meets the tube. You can be hitting with the axle tube but if you adjust the J-bar with more rake so the rear end pulls left more and then hits with the bell lessening the over all drop.

2. If it hits with one of the bolts that holds the tube in the bell, that will effect the rate of the rubber/cushion and change how it cushions and again possibly the over all travel.

3. If you adjust the bars and change steer, you may have more or less contact with the rubber and again change things like rate or overall travel. This is due to the rear end hitting farther forward or backwards on the undersling, so the cushion may need to be long front to back to hit full material all the time.

4. Just a lot more to consider on the undersling and how it contacts the rear end. Where the chain doesn't have this issues to pay attention too.

When you really look at it, the chain is less work and most likely better as you don't have to engineer it to death to make it consistent.

[billetbirdcage]

Recently been looking into nitrogen type limiters, it seems they have the ability to add in quite a bit more progressive rate than rubber, or some sort of poly / foam type pucks. Anyone running the nitrogen types?

I guess the next question is, what kind of rate are we wanting on the limiting device?

If you want my honest opinion on different limiters:

I don't really think there is a nickles difference in them, just how much lighter your wallet is.

Now I will say if you can run one that has valving to it (illegal by most sanction bodies), well I do think there is a benefit to those. Like I described earlier, the travel over time deal with different materials can be controlled/altered by having a limiter with valving, so. . . . .

[billetbirdcage]

So this all leads to something else, not talked about and maybe people don't know about them.

Position sensitive shocks

The LR valving on a std shock is linear on valving no matter where it's at on it's travel, but having a position sensitive shock allows me to control/change the valving at the point of travel it's on the limiter thus altering it or adding/subtracting valving and still meet or bypass the rules on the dampened limiter.

More things to say. . . . . hmmm.

OK, I'm done for the day (grins)

[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

[Kromulous]

One thing i would say about the 2 different spring combos is that springs at various wire diameters behave differently.

Whether you could tell a difference behind the wheel i have no idea, King1 implied there would be, but i honestly don't know.

I was late to the game with the whole light spring pre-load deal, but we love it so far.

[fastford]

thats what i cant understand about locking the heavy spring out , the reason we run a stacked left rear is to have a light spring rate with a lot of travel to keep load on tire at full droop , to me they have to work together from static ride height to full droop , i must be missing something here.......

[hucktyson]

I think a very important point that needs to be made is that NO ONE who is winning Crown Jewels is posting anything on here. I truly believe a lot of what is posted here is to baffle people with BS more than anything. I don’t even think anyone winning 10k Lucas or outlaw shows in the current era is posting anything here let alone crown jewel winning guys. We have tire loads the timing of those loads and we have rear steer ..... a bunch of different ways to generate tire loads and I’m sure different combinations of rear steer that cAn be used at different times to create different outcomes. You can try to complicate it however much you want but it still comes down to that

[hucktyson]

I hear guys talk about magic this and trick that and heard a guy during an interview say “ these shocks make more dig than anything I’ve ever felt lol. There’s a reason some guys are consistently top 5 at major events and some guys either win or DNQ ... there’s guys the fully understand what they are doing and guys who say stuff like “ these shocks make great dig “ lol

[RaceEngineer]

I have never seen a Nobel prize in physics awarded to a world 100 winner. Not even Rumley.

[fastford]

Oh , I agree with you huck , but there is knowledge to be gained on here , but the only way to gain that knowledge is to wade through all the BS , which is why i question what i dont understand......

[sidewinder69]

Exactly , nobody is looking for a setup to win the world 100. We just look for assistance to develop our own theories and knowledge .

[TeamRocket42]

Not every winning car is using a lock out nut on the left rear. The stack combo most top teams are using is nothing like I have read on this board as well. Not even close.

[hucktyson]

Many of them don’t even have a spring on the left rear. A big factor is a the huge difference an elite wheelman makes ... engineers will never fully own this sport due to the enormous variable the driver adds to the equation ... and the changing track conditions and patches of traction and patches of ice in the same corner

[Kromulous]

You can look at springs now days and pretty much guess the rates or close, and i have noticed some really thick wire diameters on the lower springs. All i can say is i tried dual 150's and a lock out and was not nearly as good as the single spring were running now. Although with the 75lb rate i did not have it pre-loaded to the degree i do now so maybe thats the difference.

Anyway great discussion, thanks to all those that share their knowledge its appreciated by me.

[TeamRocket42]

You can look at springs now days and pretty much guess the rates or close, and i have noticed some really thick wire diameters on the lower springs. All i can say is i tried dual 150's and a lock out and was not nearly as good as the single spring were running now. Although with the 75lb rate i did not have it pre-loaded to the degree i do now so maybe thats the difference. Anyway great discussion, thanks to all those that share their knowledge its appreciated by me. That's going in the right direction....500 600 700 800 lowers. I'm not going to give it all away but if you think about it some you will figure it out.