Quick valving question

chatter_splatter

Well-Known Member
I have fox 2.5 x 10 coilovers and 2 tube bypasses on the front of a crew cab Silverado. Motion ratio is 1.8 to 1, front end is 3150lbs and springs are 1500/900 with the crossover happening at 4" of uptravel. Tires are 37s @ 30 psi. 200 psi in all of the shocks.

Currently has a 0.008 flutter stack in the comp side of the coilover with a 0.012 fulcrum shim, and an 0.008 rebound stack.

Bypass has a 2x 0.015 stack on compression and 0.012 on rebound (2,1).

Rebound tube is all the way open, and compression tube is 3 turns in from open.

I'm trying to soften sharp edges and rocks but am not having much luck. Truck seems way too stiff in the small chop, but does really well in whoops and big hits. Small 3"-4" rocks sticking up out of the ground feel like sledge hammers on the frame.

What should I try next? Less bypass comp valving? No valving in c/o? More bleed in c/o piston? I know the truck will never be SXS soft, but I'm hoping there may be someone who has successfully tuned the stiffness out in the small stuff and can give some pointers.

Thanks!!
 

osidepunker

Well-Known Member
I could be wrong as I am in the process of learning this stuff myself. But it seem to me that your springs are very stiff?

I have a tundra, 4100 lbs on the front, 2.5 x 8 COs and BPs, 1.6 motion ratio, and I'm running single 800# coils. It was soft when I had 700# coils, but I was binding the coils so I had to switch to 800# and thats when it got stiff over the small stuff
 

chatter_splatter

Well-Known Member
My initial rate is actually 550lb/in and 900lb/in at 4" of uptravel. The way dual rate works is primary spring rate x secondary spring rate ÷ primary spring rate + secondary spring rate.

(P*S)/(P+S)

So in my case its (900*1500)/(2400)=562.5

So before the crossover rings engage the spring rate is very light at approx 550lbs/in, then the lower 900lb spring engages at 4" of uptravel and the rate changes to 900lb/in for the last 5" of uptravel.

It's worked really well so far. Nice and soft initially with lots of bottom out control.
 

osidepunker

Well-Known Member
ah ok, I understand about the dual coils.

So then does your coilover have any bleed holes? I have two 0.098 bleed holes in my CO pistons

Also, have you been playing with the bypass compression tube?
 

chatter_splatter

Well-Known Member
Coilovers have 2x .098 bleed holes in the piston. I started with the bypass tube all the way open, and closed it untill the truck stopped bottoming on big hits.

Right now they are 3 turns in from open. It's possible that I'm blowing through bleed travel and slamming into the bump zone, but I shouldn't be into the bump zone until about 4" of uptravel and smaller hits than that are causing problems.

I'd like to be able to hit small rock and sharp edges without taking such a pounding. One rock/pot hole sticking up isn't a big deal because it's just one hit, but when there's several of them it gets pretty bad.
 

osidepunker

Well-Known Member
ok, so when your bypass tubes were all the way open, and you were bottoming out on big hits, was it soft over the little stuff?
 

chatter_splatter

Well-Known Member
It was the same. Maybe slightly worse with it closed 3 turns, but with the tube fully open it was still pretty rough in the chop. Fox is steering me away from changing the compression valving in the bypass, but I don't know what else to really try other than taking all the valving out of the coilovers.
 

osidepunker

Well-Known Member
Well I have a similar problem as you that I am trying to work through. But I have two theories:

1. The bypass tubes when fully open can't flow enough oil and you're still passing some oil through the shims. So maybe work reduce the low speed shims in the bypass

2. reduce the low speed shims in the coilovers

you might need to add rebound also. I recently closed the rebound tubes in my rear almost all the way, 1/2 turn from close. It did smooth things out a little, although my goal was to reduce kick

Another thing is my coilover actually has a double flutter in it. Maybe you could look into something like that? Its too soft for me and I am actually changing the 1.8, 1.6, and 1.4 to 0.15 shims

20190724_064436.jpg
 

chatter_splatter

Well-Known Member
Theory 1 is what I was also thinking, and I emailed fox and asked them if I should reduce bypass valving and they said no, and to reduce the rebound valving. They said the compression tube should be able to flow enough oil and the valving won't outrun it.

Theory 2 could be possible, but this is what I have in the coilover.

.800 x .020
.950 x .008
1.100 x .008
1.350 x .008
1.425 x .008
1.600 x .010
Piston
1.800 x .008
.950 x .012
1.600 x .008
1.425 x .008
1.35 x .008
1.100 x .008
.950 x. 008
.800 x .020 (x2)
Rate plate

It's pretty light, and the only way to make it lighter would be removing shims or making the fulcrum shim thicker.
 

osidepunker

Well-Known Member
that seems super light lol

Maybe you should still look at the springs? Your truck is 1000 lbs lighter than mine on the front. Maybe a combined initial rate of 550# is still heavy? Or maybe its too light and you're feeling the bumps run into the secondary 900# rate?

But I'll shut up now haha Like I said, I'm still trying to learn this stuff and now I've run out of ideas
 

chatter_splatter

Well-Known Member
Haha I've run out of ideas too so keep throwing em if you've got em.

550lb/in is light enough to move the front end of the truck up and down a few inches by hand. Mazzulla recommended an 800lb spring to start with, but I really wanted dual rate so I did some digging and found some springs that would work. The motion ratio on this kit is almost 2 to 1 so it needs a pretty hefty spring. It used to have 850s and it was way worse in the chop. The dual rate has helped tremendously, but I still feel that I'm having harshness from the valving. I would absolutely recommend going to dual rate if you have the room for it on the shock, but it is a little spendy.
 

osidepunker

Well-Known Member
yeah I really want want dual rate, but I have 8" shocks so they wouldn't be as effective. Plus, they don't make a small coil that stiff enough for how heavy my truck is (8000 lbs total, 4100 on the front)

what N2 pressures are you running?
 

chatter_splatter

Well-Known Member
That is crazy heavy! I think you've probably got the best option already on the truck.

I'm running 200psi all the way around. I've thought about dropping pressure to 150, but everyone I've talked to says to avoid tuning with shock pressure and to stay at 200 for fox's. Kings actually cavitate at high shaft speeds with 150psi but that could be intentional.
 

osidepunker

Well-Known Member
Haha yeah I know. I have skids sliders winch etc

I have to run low flow pistons in the bypasses with 4.3.2 stacks. I'm currently revalving them to try and tune out some of the harshness over the little stuff

Yeah I just wanted to make sure you weren't over 200 psi. I agree, keep it them there and work on valving or whatever
 

chatter_splatter

Well-Known Member
I do wonder if I should take the truck out and beat on it, then adjust the shocks to 200psi. It does feel like it gets a bit stiffer when the shocks get warm.

But I think 200psi cold is what it's supposed to be.

Have you tried a thicker 0.012 or 0.015 fulcrum shim on the coilover flutter?
 

osidepunker

Well-Known Member
Yeah 200 psi cold is what I run

I'm gonna take off the bypasses first and run just the coilovers. I want to see if it's the bypasses causing harshness or the coilovers shims/coils. If it's the coilovers then I'm going to start playing with the stacks. I don't have a choice on the coils so it might be possible that I'll just have to deal with it
 

chatter_splatter

Well-Known Member
What's the science behind the double flutter on yours? Looks kinda like something Accutune would do.

You might try just the 1.8 before the fulcrum shim to reduce the crack pressure and eliminate the 1.6.

1.800 x .010
.800 x .008
1.600 x .010
.800 x .008
1.60 x .010
1.425 x .010

I think reducing the crack pressure might get the oil moving through the piston sooner and soften up the initial hit.

One guy suggested I try a flutter in the bypass for the same reason. Said the oil in the tube and the poppet has mass, so it helps to crack open the valving on the piston sooner so it doesn't have to get all of that oil moving and open the valve.

Not sure how I feel about a flutter in the bypass, but I might try it.
 

cosmo

Super Moderator
How are you checking your gas pressure? At full droop, or? Do you have the proper gage or just winging it with the tanks gage? You can drop gas pressure down to 175 psi.
 

chatter_splatter

Well-Known Member
I'm filling with a no loss gauge and 300 psi regulator at ride height cold.

Is it possible having the bypasses too loose on compression will cause harshness?
 
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