stack spring

[riddle28]

new on this, on a rf setup. i run between a 350-400 standard spring with a Christmas tree bump. if i swap to a stack how do i have any clue where a good starting point is? and say you put one on and feel like the car tight in and needs more spring, do you adjust the softer spring or the heavier or the lockout point? all this is new to me and not much info out there

[Matt49]

new on this, on a rf setup. i run between a 350-400 standard spring with a Christmas tree bump. if i swap to a stack how do i have any clue where a good starting point is? and say you put one on and feel like the car tight in and needs more spring, do you adjust the softer spring or the heavier or the lockout point? all this is new to me and not much info out there

It is very dependent on your car and the rest of your setup. No easy answers. You also need to know how much travel you are currently getting and what your load is at that travel. And if you're actually getting down on that bump you'll need a spring smasher to figure this stuff out.

[riddle28]

ive got a smasher 4.25 im around 2300 usually. am i just looking for a smoother curve with around the same final load #?

[Punisher88]

With a 250/400 and locked out I'm typically at like 1450 to 1500 3" and 1900 to 2000 4" the that would maybe ballpark you to 2300 at 4.25. With a white with red stripe 75 bump.

[riddle28]

thanks alot punisher. i was just wanting a ballpark of what im looking for since theres so many combos

[Punisher88]

You just dont want your 3" super soft with a high 4" because then it will hot that 4" with a spike and shear traction and cause a horrible push.

[Punisher88]

I've always kept mine within 5 to 600 I think of what the 4" is. There's certainly people on here with more knowledge than me, and may have better info and say I'm way off. But I've never shared traction because I spike the rf load with those numbers. Not saying you cant go to a softer 3" I just haven't tried it to know how soft is too soft.

[MasterSbilt_Racer]

700# from 3" to 4" is acceptable

[Kromulous]

A lot of good info there.

I have always loved stacks, my Brother seems to drive better on them, over the single soft springs.

I usually ran like 600/400 (240 rate) and lock it around 7/8's to 1 inch travel. Then sometimes a small bump as well.

You will need a shock with some rebound to control that 600lb spring after it gets to be the primary spring thou.

[hipower17]

what lenght would the springs be for this like for a bg rocket rt. front takes a 12" spring what lenghts of spring would you need for this. i've never worked with a stack setup. thanks for any info

[RaceEngineer]

what lenght would the springs be for this like for a bg rocket rt. front takes a 12" spring what lenghts of spring would you need for this. i've never worked with a stack setup. thanks for any info

It depends on the rates you use. 6 and a 7 are fairly common. Or 6 and a 8.

[Twenty-Five]

What is the theory behind using a stack vs a single spring if your 4 inch number and ride number remain the same?

[Jking24]

Short answer You can have a much softer rate initially to promote early travel without concern of coil bind. And you can tailor the curve to your needs much easier.

[Jking24]

Also just because your four inch number is the same does not mean the car will act the same if you have a high three inch the car may under travel.vs if you have a lower three inch the car may over travel all with the same 4" number. Just one example

[fastford]

What is the theory behind using a stack vs a single spring if your 4 inch number and ride number remain the same?

every one has a different answer to this , to me ,and not getting into the physics of it , it has a lot to do with the track your running on , on a smooth slick track , i still think a single soft spring and a bump stop is better , on a rough track , i like the two stage ( stacked) set up . JMO

[Matt49]

An important thing to keep in mind is that while we talk about a load at a certain travel, what we really care about is travel at a certain load.
The same goes for shocks. We talk in terms of force at a certain speed but it is more important to understand the speed given a force input.
The force around the corner is what remains a constant for the most part so everything we change on the shocks and springs dictates travel and how fast it gets there, not the other way around.

[Kwhardage]

An important thing to keep in mind is that while we talk about a load at a certain travel, what we really care about is travel at a certain load.
The same goes for shocks. We talk in terms of force at a certain speed but it is more important to understand the speed given a force input.
The force around the corner is what remains a constant for the most part so everything we change on the shocks and springs dictates travel and how fast it gets there, not the other way around.

Been trying to explain that one for a while. Especially getting quoted numbers in the 2600-2800 range for 4" and 4.25". I'm sure somewhere might see that, but the dustbowls around here wont be anywhere close to that.

[Austin34471]

An important thing to keep in mind is that while we talk about a load at a certain travel, what we really care about is travel at a certain load.
The same goes for shocks. We talk in terms of force at a certain speed but it is more important to understand the speed given a force input.
The force around the corner is what remains a constant for the most part so everything we change on the shocks and springs dictates travel and how fast it gets there, not the other way around.

This^

Just because you have a 4,000 lb load number at 4in does NOT mean you are jamming your RF into the ground harder than every other car.

@Twenty-Five, If the car spent the entire lap at 4", then it wouldn't matter. But 4" (in this scenario) is the MAX travel/Load. Most of the way around the track, you are somewhere in between ride height and your maximum.

For example, Lets say ride height load is 800, you travel to 2400, and your nose bottoms out at 4" of RF shock travel.

Option A is a: 400lb/in spring with no bump, which you would have to wind down 2 inches to get your ride height number(800#), then traveling 4" from there would get you to 2400# max load (800 ride height + (400lb spring)x(4in of travel)=2400.)
So your loads would look like:
RH: 800
1": 1200
2": 1600
3": 2000
4" :2400

Option B is a: 150lb/in spring with a 1000lb/in stiff bump spring. You would have to wind it down 8" to get it to hold at ride height. What would happen is, you would have to have this bumpstop shimmed to hit at 3" so that you would hit 2400# at 4". So your loads would look like:
RH: 800
1": 950
2": 1100
3": 1250
---hits bump, add 1000lbs for last inch on top of 150# of primary spring
4": 2400

both options give you the same ride height and max load travels, BUT what happens when you're on corner exit, starting to straighten out, and the track/car setup only provides 1600# of force to the compressing the RF? Where will both of those 2 options be as far as travel? What will that do to your dynamic wedge? What else might it effect?

[billetbirdcage]

This almost exactly the rates Austin used above. Red is the stiffer rate and thus higher 3" numbers but the same basic numbers after 4"




Same car, same night just different RF spring combo's during a private test session

[Drop Shock]

“Anything over 1900 pounds at 4 inches is junk” - Scott Bloomquist