How much Preload is too much?

Hey guys,

So we’d all like to have a nice soft ride but obviously running like a 400lb spring isn’t practical without running like 8in of preload. So how many LBS of preload is too much?
ASSUMING the arms are strapped so the piston doesn’t hit the shock bottom)?
ASSUMING a NEW setup (sizing the springs accordingly) so assuming keeping the same rideheight)
ASSUMING no coil binding

(Yes I know adding more preload to an existing setup adds to ride height and locates the piston lower in the shock reducing remaining downtravel.



Current spring compressions: (600lb 13” ):
At Droop preload: 2.25” (1350lbs)
At Ride height: 4.25” (2550lbs)


I just got new shocks (long travel) and Im trying to decide on the rates (dual rate setup)

I ran the numbers and here’s what Id have to run to maintain the same rideheight (2550lb):

500/600: 6.75” (1840lbs) at strapped max droop
600/700: 5.35” (1728lbs) at strapped max droop
800/700: 2.55” (952lbs) preload [4.3” (1605lbs) at strapped max droop]

*Note: the preload lengths include preload from the top ring plus pre-squeezed springs. [current arms are keeping me strapped 1.75” up from coilover full shock length, but that will change soon]

Additional info:
Truck:
Double cab Tacoma 4.0 4wd 2nd gen
Heavy plate bumper, supercharger, and winch up front
12-14” long travel.
Bypasses soon to come.
Mixed on/offroad, no racing yet.

Any info would be greatly appreciated!

**** Update: So using all my measurements and available spring rates/sizes I graphed the new potential spring rates. Honestly really don't see a huge difference between the new options. But uploaded it for ref.

 

What you want to avoid is spring bind. As long as there's some space between each wrap of the coil when the suspension is fully compressed your ok. When the coil compresses so much that theres metal to metal contact thats no good and can cause permanent damage to the spring.

 

Yep! I know. All of those are assuming no coil binds. I actually cant even run the 500/600 without coil bind if I keep the same ride height, so that ones already kind of eliminated : /

 

You could do a longer 750lb spring and then a shorter, let's say 400-450lb spring for when your driving on the street. That might give you the ride quality that you're looking for. I've seen people do it before but not sure how they deal with the spring bind when the light spring maxes out?

 

You could also revalve the shock. You should do this anyway if you are changing springs. Add a flutter stack on 1st compression valve, helps alot.

 

I ended up ordering 800 10in tops and 14in 700 bottoms. it was only 20lbs different (373 vs 353) for the bottom rate then 700 from wherever I put the spacer. I was told it would be too stiff but 20lbs per inch is pretty minimal, and it allows me to get a large range of adjustability (including running the 373 rate for almost the entire travel if I want it really soft. I actually mapped out the range of what I can run without coil bind, including a 1" drop in ride height:

And yeah, I'm onto deciding valving now. Going to start SUPER soft with #30 flutter stack compression and #35 flutter rebound for the coil carrier (then #35 comp and #50 rebound in the bypass). I'm not sure how that'll work but Ill step them up as I go. I don't jump or anything so I'm fine with softer damping and springs for a smooth ride.

 

I don't think you want to flutter the rebound, I could be wrong. Coil springs behave different than leafs, they store and release energy (bumps/jumps) very quickly, unlike leafs, where you can run less rebound so gravity actually pulls the axle down. The last few inches of leaf are very light spring rate, so it doesn't drop out as quick as you want to get ready for next hit. I could be wrong, I'm still learning. But I know flutter on comprehensive stack is very noticeable and handles much better/more comfortable here on Az jeep trails.

 

I revalved my rear shocks, added 1 flutter on 1st valve and pulled a double stack from the middle of pack. All of a sudden rear out performed the front, I was laughing like the Joker to my self in the desert! I couldn't believe that small change made a very noticeable difference. I could literally feel the rear end hooking up better, buy with less bumps in the cab. I literally can NOT feel a cattle guard in the rear when driving over it. Just rebuilt front, will see soon how she feels.

 

Yeah that all sounds right/familiar. My only reasoning for running flutter on the rebound is because itll be the coil carrier, Ill have the bypasses doing most of the work. However I'm definitely still on the fence about it and very much open to just sticking with a regular like #35 or so.

What do you mean you pulled a double stack from the middle? did you remove one of the shims completely so youre running a shorter stack? What is it a 30?

Yeah that's the kind of thing I'm shooting for, we have a lot of washboard and rough pot-holey roads around here (so sharp hard high velocity small hits) so I'm definitely going to be funning flutter stacks. I'm also putting the factory 9 hole high flow pistons in them to hopefully help as well. But I am however finding it hard to figure out a valving for a basically Cadillac smooth ride without opening it up to bottoming out or excessive body roll

 

The rear had a double stack, or two of the same shim. I took this out, as it would translate to a spike or drop in the middle of a graph, indicating more resistance

You will just have to take your best guess, drive it, then adjust from there. External adjustable shocks are helpful, bypasses and resi clickers will help dial it in.

The Cadillac will be in the valving, maybe go double flutter.

 

No need to flutter the rebound

 

even on the coil carrier?

 

Yes, even more so since you stated you'll be using bypasses as well. The bypasses will be in charge of most of the adjusting.

 

got any recommendations on the valving? Was thinking Coil Carrier: #30 flutter compression, #35 rebound Bypass: #35 comp, #50 rebound

 

I don't know those numbers, I'm familiar with King Shocks shim measurements. It's by the thousandths. What is the measurement of the shims for the shocks you're using?

 

#30 is .008 #50 is .010

 

I can't give you any ainput for that as I don't run bypasses. I just use a coilovers. But on my coilovers I run 8/12 valving, that's pretty soft. I see more road than dirt so I optimized it for what it gets used for the most. In your case I'd go a little stiffer. Maybe 10/15? And a 20 on the flutter is what I've heard most people use. And all of this is thousandths by the way.