Shock Tech

AssBurns

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This is probably going to be a wall of text but hopefully some of you learn something new and it helps in some way in the future. These are things that I’ve found tinkering on my own and others vehicles over the past 10ish years.

Shims adjust how the piston travels through the oil of the shock. Thicker the shim, the more dampening you get. Thinner the shim, the less. Pretty simple. Oil weights also play a large factor in this but I’ve only ever ran one type of fluid in an off-road truck shock. It’s all about limiting the flow of oil through the piston.

It’ll probably be helpful if you know the terms before I start explaining what little I know, most of these can be found by googling if you don’t understand it.

Compression dampening is what keeps you from smashing into your bump stops. Stiffer valving is better for go fast, but you need to tune it to be comfortable. It’s great if you can speed through dips and whoops but not if it comes at the cost of your back.

Free bleeds for the most part should be left alone from what I’ve read and experienced. On my rears I only have 1 of 4 bleed holes open, by doing this you restrict fluid flow a lot. Restricting fluid flow causes cavitation on hard hits and the oil to move a lot more in the resi and can cause a lot of damage to your shocks(this is why resi ifp depth is very important for all shocks, top mounted resi most importantly). Can be combatted by adding nitrogen to your resi cans, but it isn’t always the best option. My first revalving I did of my 4runner when it was completely stock other than the shocks and tires was to try and make it quick and comfy on Fox 2.0rr shocks. 6.5” travel shocks in front and 10” travel shocks in rear. I ended up having to run 350psi of nitrogen to combat the cavitation and shock fade after a few miles, but it rode awesome. Could skip across stuff in Barstow and Lucerne almost as fast and guys with LT. only drawback was all that valving in the tiny shock caused a lot of cavitation even with 350psi of nitrogen and would cook the seals out of the shocks every long trip. After years of this I finally said fuck it I wanna go fast so that’s when LT happened.

The small shocks are fine if your vehicle isn’t heavy and you’re not trying to haul ass. A Toyota 2wd pickup can be incredibly fast on 2.5 shocks if it’s built with weight in mind and valved appropriately. Hell even on 2.0s if it’s light enough. The heavier the vehicle the more shock you need because you need dampening to combat the weight of the vehicle pushing down. Not necessarily spring rate, but shock valving. Springs should be picked for weight of the vehicle, shocks for type of terrain.

Let’s get back into compression valving.
If you have a standard .015 stack on your compression side of the piston that’s probably really good. Might be a little stiff in the shorter quicker bumps, so you combat that with a flutter stack or a mixed stack. Let’s use fox standard shim sizes for 2.0 shocks cause that’s what I know off the top of my head.

Compression side
•Rate plate
-.800” diameter
—.950
—-1.100
——1.350
——-1.425
———1.600
-piston
———1.425
——-1.350
——1.100
—-.950
—.800
-.750 “backup” washer
Rebound side*

Between the 1.350 and the 1.100 shim on the comp side id insert a .020”x.800” shim to create a flutter, this will allow those larger base shims to open up sooner and allow fluid flow on the short quick hits like washboard, small rocks, potholes and such. If .020 is too much and I felt like that was also making it blow through travel, I’d go with .015 or .010” thick. You can also shorten shim stacks from but ALWAYS use the larger base shims. You can add more base shims to have a stiffer “zone” before the shims flex past the flutter and engage the rest of the stack. That’s what’s so fun about tuning shocks, there’s nearly endless ways to adjust the shims. You can create two or three zones using flutter stacks, at one point in the front of my 4runner when it has stock length arms I had a double flutter and it rode really great, but I had to ditch that when I put the longer arms on it.

Flexible rate plates are something I’ve fooled around with only a little bit. From my understanding it makes the shock not hit it’s harshest “zone” so violently. Instead it hits and flexes the rate plate to allow a smoother feeling of hard hits. The hard part it making it flex enough to accomplish this and not blow through your travel and bump so hard you piss blood.

There’s fulcrum shims that allow freebleeding. It’s when you put a .800” shim of whatever thickness you desire between the comp side of the piston and the largest shim. This allows the fluid to flow past the fulcrum and not engage the stack for smaller bumps like washboard and small rocks. I liked .010 fulcrum with a .015 compression stack for trail driving. The fulcrum shim method works well, but increases the overall fluid flow when hitting hard because it increases distance between the piston and it’s largest shim. Flutters just allow the base of the stack to open a little easier to allow the smaller hits to not engage the entire stack.

Mixed stacks work well too. You can have a .020/.015 mixed stack to allow the stack to be more progressive.

Rebound valving is something that I haven’t spent a whole shit ton of time on. I usually just valve it around what I see is needed for the spring rate I have. Usually .012 or so shim stack and it works fine, if you’re on leaf springs you need much less, probably .008 shims. You want your wheels to stay in contact with the ground as much as possible to maintain speed and not load/unload your drivetrain constantly, keeping you from ruining axels and driveshafts and transmission parts. You want it quick enough to maintain a good amount of contact, not so quick you get the classic pogo stick esque donkey kick that sends your rear end up and over the front. This is caused usually by too heavy of rebound allowing the suspension to “pack” and not droop enough to have enough compression travel to dampen the next hit. This happens a lot, most of the time it’ll be okay if your shocks are tuned right, also has to do with comp valving to make sure you’re not bottoming so fast that you’re hitting bump stops constantly anyway.

A lot of people have their own methods and may differ completely from what I’ve done and what I like. I personally like light rebound in the front to keep the front from diving and packing, almost making it feel like it’s growing through whoops. The rear I like to be controlled but light to keep the rear tires planted, but again no so light that the springs can push the shocks open so quickly that the rear will pogo.

Bypasses are something that I’ve messed with only a few times, the more tubes the better. They allow different dampening zones at different dampening rates which is awesome, you don’t have to pull the shocks apart all the time. You set your baseline valving for your trucks weight and driving style and you then adjust the bypass valves in or out to make it handle better. I’ve played with fox’s internal bypass that utilizes holes covered by different thickness reeds. These are the ones that come on raptors. IMO they’re cool but overall I’d go with an external bypass because why open the shocks to tune if you can leave them closed.

Hydro Bump stops are truly one of the best things to ever happen to off-road. I haven’t spent a lot of time on tuning them because it’s not really needed. It’s a tiny shock that’s valved to hell. I put the appropriate amount of fluid and fill them to 200psi of nitrogen and call it good.

To end id like to say it’s not all about wheel travel numbers, it’s about how you set your truck up and how to tune your shocks. There are guys that have 9 inches of travel and can haul absolute ass. With stock arms I was making I think 8” up front and 13” in the rear. Everyone I took for a ride said it was ridiculously smooth *for a stock truck*. Yeah, it was a little rough till it got up to speed, but I could cruise through washes of Barstow at a good speed and my back never hurt after the trip.

I think I covered most of what I know, if anyone has any questions feel free to ask.

Also I’d like to add I’m selling a set of 2.0x6.5” fox remote reservoir shocks, if you’re interested let me know. Fit perfect in stock length arm trucks and 4runners 86-95.
All great stuff! Thanks for sharing. Have you messed with location of the flutter shim at all to tune where you want it to start engaging in the stack? I think I really need that in the rear of my 7100's. The low speed stuff is actually pretty nice, but I need a little more high speed dampening. I was thinking of swapping the top two shims for some stiffer ones, then add a thin flutter shim halfway up the stack.
 

DeltaBravo

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I need some aftermarket suspensions on my rolling dumpster. Got the 4600s. Idk man BP51s look good and shit but everyone knows that KANGS is for the baller shit.

Joking aside, I want something decent for on and off road and would be an improvement over the 4600s
 

Itaro

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I need some aftermarket suspensions on my rolling dumpster. Got the 4600s. Idk man BP51s look good and shit but everyone knows that KANGS is for the baller shit.

Joking aside, I want something decent for on and off road and would be an improvement over the 4600s
Decent - 5100s. Or 6112/5160 (the old second gen Baja/Pro setup)

Past that then it’s fox/icon/king/etc. Depending on your budget
 
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All great stuff! Thanks for sharing. Have you messed with location of the flutter shim at all to tune where you want it to start engaging in the stack? I think I really need that in the rear of my 7100's. The low speed stuff is actually pretty nice, but I need a little more high speed dampening. I was thinking of swapping the top two shims for some stiffer ones, then add a thin flutter shim halfway up the stack.

what is your current stack looking like?

I have messed with flutters ALOT and have tried moving them around on the stack. You get different “progressive” feeling dependent on where in the stack you place it. Closer to the piston the sooner the stack will be engaged. If you want a little more dampening on harder hits I’d suggest starting with you stack you have and adding the metric equivalent of a .008x.800 shim between the 3rd shim from the base and the 4th to start with. This may make the suspension feel softer till you hit a hard hit, if you don’t like it go up one thickness across the entire shim stack except for the .008x.800 shim for the flutter.
 
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madtaco461

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I have king 2.5" x16" smooth bodies in the rear that tame 62" leafs. I have a 8 stack rebound and 15s for compression. I can hit big whoops pretty well, but the wash board stuff I can't do. Can a flutter stack help me out with the high speed damping. Or is it as simple as changing out my smaller shims with something lighter like 12s or maybe 10s.
 
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I have king 2.5" x16" smooth bodies in the rear that tame 62" leafs. I have a 8 stack rebound and 15s for compression. I can hit big whoops pretty well, but the wash board stuff I can't do. Can a flutter stack help me out with the high speed damping. Or is it as simple as changing out my smaller shims with something lighter like 12s or maybe 10s.

a flutter can definitely help with something like that. Going to 12s will allow it to blow through the travel faster and may cause packing and might cause the ol’ donkey kick. You can try a .010 or .015x.008 shim between the 2nd and 3rd shims from the piston and that should help a bit. I’m pretty sure those are Kings OD size as well as fox. If not the one you use as a flutter is usually the smallest OD shim available for your shocks. Remember that it’s good to go in small increments. Start with a .010” thick and see if it helps, also are you airing your tires down? May seem like a dumb one but you’d be surprised how many people actually expect a smooth ride with 35 psi in their tires.
 

madtaco461

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a flutter can definitely help with something like that. Going to 12s will allow it to blow through the travel faster and may cause packing and might cause the ol’ donkey kick. You can try a .010 or .015x.008 shim between the 2nd and 3rd shims from the piston and that should help a bit. I’m pretty sure those are Kings OD size as well as fox. If not the one you use as a flutter is usually the smallest OD shim available for your shocks. Remember that it’s good to go in small increments. Start with a .010” thick and see if it helps, also are you airing your tires down? May seem like a dumb one but you’d be surprised how many people actually expect a smooth ride with 35 psi in their tires.

Yeah my hard dirt pressure is about 25 psi. 33x12.5r15. Truck is about 4K lbs. I might try a slight flutter. Made some changes to the truck so I’ll baseline first and go from there. That 4 inch road chop makes my rear slide around once I get above 60 mph. Kinda feels like the truck is on ice.
 
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Yeah my hard dirt pressure is about 25 psi. 33x12.5r15. Truck is about 4K lbs. I might try a slight flutter. Made some changes to the truck so I’ll baseline first and go from there. That 4 inch road chop makes my rear slide around once I get above 60 mph. Kinda feels like the truck is on ice.
Try a bit lower psi, I bet it will help a lot. And when it comes to road chop/washboard flutters definitely help a lot. I don’t know if it’ll help with the skating feeling going fast on those roads, always figured it’s just how it is going fast on hard pack with loose stuff on top.
 

Arcticelf

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Shock packaging question: other than having to cut through the bed can anyone think of a reason not to put shock tabs off the u-bolt plate?

This is going on the back of a 2nd gen taco with leaf springs.

This will let me solve all clearance issues between the leaf pack/ubolt plate and the shock, (because the shock is above all that), which gives me more useful space between the frame and tire for the shock body. So I can stop rubbing the tire on the shock.

The downside is that I'll have to cut the wheel well and poke the shock into the bed.

Am I missing anything?
 

Stairgod

Two bad decisions away from buying a bulldozer
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No downside that I can see. U bolt plate is definitely a strong enough mount.
 
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Shock packaging question: other than having to cut through the bed can anyone think of a reason not to put shock tabs off the u-bolt plate?

This is going on the back of a 2nd gen taco with leaf springs.

This will let me solve all clearance issues between the leaf pack/ubolt plate and the shock, (because the shock is above all that), which gives me more useful space between the frame and tire for the shock body. So I can stop rubbing the tire on the shock.

The downside is that I'll have to cut the wheel well and poke the shock into the bed.

Am I missing anything?
Everyone I've seen with SOA bumps off that plate. What plans do you have for your bumps?
 

Arcticelf

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Everyone I've seen with SOA bumps off that plate. What plans do you have for your bumps?

I'll run a hydro bump off the center plate, but I should have room to put the shock tabs off the front edge.

Hanging the shock off that plate with a 1/4" tab should be similar to hanging it off the axle with a similar tab.
 

AssBurns

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Did some revalving on my rear shocks. I've been wanting to do this for the last few months after I did the engine cage and moved the batter to the rear. It felt too soft almost all the way through Especially on the harder hits it would hit bumps too quickly. I think it handled washboard nicely, but is hard to tell when the front are shot. When going through roller whoops at slow speed, I would bounce off the bumps and my rear end seemed to bounce way up. I figured I probably needed more rebound dampening in the slow speed, and more compression in the high speed. (I could be totally wrong on this. This is my first attempt and getting creative with the two sets of shim stacks I had available.

Here's the 3 different combos I ran so far. The first one was what I bought the shocks with. The second one is when I revalved this past summer.

1578555771451.png
 
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Any first hand experience with FOA shocks since they upgraded their facility and fixed a lot of their QC issues? I know the price seems too good to be true but for a 20 year old truck that'd be a weekend toy during the cooler months of the year i really don't know if fox/king/radflow/ads/stayaway would be justifiable. Shit for like 1200 i can have 12" 2.5 coilovers AND 16" 2.0 smoothies lol.
 

AssBurns

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Any first hand experience with FOA shocks since they upgraded their facility and fixed a lot of their QC issues? I know the price seems too good to be true but for a 20 year old truck that'd be a weekend toy during the cooler months of the year i really don't know if fox/king/radflow/ads/stayaway would be justifiable. Shit for like 1200 i can have 12" 2.5 coilovers AND 16" 2.0 smoothies lol.
I have a buddy that picked up a set on his Jeep less than a year ago. I don’t think he’s had any issues yet, but still early on.

not sure I’d want to invest in FOA’s but for the price it’s not too risky. Make sure you have the tools and nitrogen tank to rebuild them if needed at some point.
 
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yea I do have the stuff for rebuilds minus a nitrogen setup but thats not a big deal. I did some googling and there isn't a ton of newer info on them other than i saw the owner post that they updated machinery/started outsourcing parts to make QC better. BUT can they be that shitty to ruin a 6k$ front setup? i guess if they show up leaking thats my answer lol.
 

Arcticelf

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yea I do have the stuff for rebuilds minus a nitrogen setup but thats not a big deal. I did some googling and there isn't a ton of newer info on them other than i saw the owner post that they updated machinery/started outsourcing parts to make QC better. BUT can they be that shitty to ruin a 6k$ front setup? i guess if they show up leaking thats my answer lol.
Worst they can do is not provide.any dampening.

I'm thinking of giving them a try for a buggy I'm building.
 

AssBurns

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Picked up a nitrogen tank, regulator and a short 6' hose so I can get working on revalving these shocks. Now that I have a little more dampening up front the, the rear is too soft. My plan is to stiffen the front to something more progressive, and do the same in the rear while also destroking my bump stop from 3" to 2". I have some shims leftover from last time a revalved the 7100's so I'll probably do that tonight after work. Still waiting for ICON to get back to me. I called them yesterday to get some shims and they are taking a while to get an order together. I called today, and they got my email with my info, but I guess they are too busy to get a simple order together within 24 hours. Sorta disappointing since I'm wanting to get these done before this weekend.
 

Stairgod

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Picked up a nitrogen tank, regulator and a short 6' hose so I can get working on revalving these shocks. Now that I have a little more dampening up front the, the rear is too soft. My plan is to stiffen the front to something more progressive, and do the same in the rear while also destroking my bump stop from 3" to 2". I have some shims leftover from last time a revalved the 7100's so I'll probably do that tonight after work. Still waiting for ICON to get back to me. I called them yesterday to get some shims and they are taking a while to get an order together. I called today, and they got my email with my info, but I guess they are too busy to get a simple order together within 24 hours. Sorta disappointing since I'm wanting to get these done before this weekend.
Fwiw, if you already have Argon tanks(I.e. pure Argon for TIG for instance) no need to buy Nitrogen. Not that much cheaper for the gas, however having to buy another tank for a different gas is some $$
 

AssBurns

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Fwiw, if you already have Argon tanks(I.e. pure Argon for TIG for instance) no need to buy Nitrogen. Not that much cheaper for the gas, however having to buy another tank for a different gas is some $$
Didn’t know you could use Argon for shocks. Guessing it doesn’t expand with heat like nitrogen?

I don’t have an argon tank so I’m at square one with all this.
 
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