2005 Tundra novice build - "The Rez"

smokeysevin

Observer
Sean - I had my shocks rebuilt and revalved a year ago. Did they give you a sheet with the shim stack information on it? They hadn't been done prior to that as far as I'm aware (bought them used). I had them adjust the valving so the low speed compression was improved. The shop that rebuilt them said that I couldn't change the digressive valve to a progressive. You can change the rate of the valving by swapping the shims, you can also (probably) swap the pistons from the fox shock to the icon shock, basically they need to have a similar height and the same wear band size. FOA shocks can take some king parts for instance. The pistons aren't terribly expensive anyways. I ordered Icon shafts when I did my rebuild and they were like $60 each. Pistons are ~$20-40. Basically you can only make a 2.5" shock for the same application different from any other in a few ways. If you make the ID of the body different you have to run different seals and you have to machine the ID more or less which costs money. The way the piston sits on the shaft could be different as could thread size and things like that but there is not really anything special about any brand other than QC. I don't know enough about this to know if that's correct or not. The ride remained basically unchanged, which tells me the springs are likely the problem. I would be interested in what the current valving is before making that statement but you could be right.

The more I look at it and read up on it, I'm leaning towards swapping my 700 lbs springs to 650 lbs. I have the original #650's that the Icon shocks came with and might try to swap them over. They are 13", which is kind of annoying, but a swap would tell me if I could get my ride height back and have an improved ride. If I'm understanding all this correctly the spring length doesn't necessarily matter, more just the rate. I should still be able to preload the 13" #650 springs to get to my ride height (2" above stock) and they should theoretically be softer than the #700's at that height. Not necessarily, spring length is sort of independent in that excess is not needed. If you go too short thought you will fully compress and block out the springs. If you have uncompressed spring at the fully bottomed out point after the preload is applied you are ok and extra length doesn't help.

Here's some decent reading I found: https://accutuneoffroad.com/articles/coilover-spring-rates-for-toyota-tacoma-4runner/. Since the 1st gen Tundra is heavier than a Tacoma I'd say 650 for me would equal 600 for them. Maybe? I don't have immediate plans to add full skids, and will be keeping my bed open and clear. I don't think I'll have much more weight than I already do. Rate depends on the length of the control arm, the position of the shock from the control arm pivot, and weight that the truck needs to support.

The FOA reservoir has me intrigued. When I had the shocks rebuilt I inquired about adding a remote resi and the cost just didn't make sense. If I could add them myself I'd really consider it. I'm sure I can find a place that works with hydraulics around here....tons of tractors for farming in this area. That can come later though. I ought to be able to get a decent ride with what I have now if I can figure out what I need to do. I looked into just using the stock icon DR fill port to add a resi and the hole was on the small side. If you are ok punching that out for a 1/2" NPT hydraulic fitting then you can run the resi I linked above. I almost went that route but opted to wait because I plan to sell the DR/Icon's I have once I secure a LT kit.


I'm not following you here. Did you mean to say I have too little rebound damping? Bucking would be a decent way to describe what I'm feeling. Lots of feedback from the rear end. The only way to adjust this is to revalve, correct? This is what I have on there currently: http://iconvehicledynamics.com/shop/943-2000-2006-toyota-tundra-vs-25-series-pbr-rear-shocks-wcdcv-0-3-lift.html

bucking is when you compress the rear then feel the rear end bounce back up really quickly, the wobble or sliding loose feeling is when the back sort of sinks or slides because the springs don't extend back down quick enough.

My tire pressure is 35 front and 33 rear (chalk test), and they are E-rated (285-75/16)
seems about right.
More on valving.




Sean
 

Kpack

Adventurer
The only information I have is that they replaced some of the shims with these:

1.550 shims x2 per side
1.425 shims x1 per side

No idea what the factory shims are/were or what these replaced.
 

Kpack

Adventurer
Just went out and measured a couple of things, because I was curious as to where my #700 springs are at right now.

Uncompressed length = 14"
Installed length = 12"
Length with truck weight (ride height) = 10"
Length of threads showing = 1.5"

Now I'm really wondering what #650 at 13" will look like. According to Icon, the max preload on the #650 13" is 2.375" of threads showing. Not sure if I can get my ride height on the lower spring rate.
 

tennesseewj

Observer
So if I'm reading that correctly you've got 2800# of static load on each front coil, right? 700# per inch, compressed 4" total at ride height.

I don't have anything to compare it to, but that number seems high compared to the curb weight of the truck.

Maybe I'm not interpreting that concept correctly, though.

Sent from my Pixel 2 using Tapatalk
 

smokeysevin

Observer
So if I'm reading that correctly you've got 2800# of static load on each front coil, right? 700# per inch, compressed 4" total at ride height.

I don't have anything to compare it to, but that number seems high compared to the curb weight of the truck.

Maybe I'm not interpreting that concept correctly, though.

Sent from my Pixel 2 using Tapatalk
This is going to be an approximation so consider the numbers arbitrary

If the truck weighs 5600lbs
say 60% is on the front

5600X0.60 = 3360lbs over the front

Start by splitting the truck in half along the driveshaft axis, so we divide that by 2 (one spring per side)

3360/2=1680lbs we need to support with each coilover

Since the arm of the truck doesn't have the shock out at the wheel it becomes a moment balance problem.

Basically we take the weight we need to hold up and multiply it from the distance to the pivot point

1680lbs*12in=20,160in-lbs

Now we set that equal to the distance that the shock is to the pivot point times the force the arm sees at the shock

20,160in-lbs=<TOTAL SPRING FORCE>*9in

20,160in-lbs/9in=<TOTAL SPRING FORCE>= 2240lbs

Now we take this number and say if we want a spring rate of 700lb/in what is the preload required?

2240lbs/700lb/in=3.2in

Conversely you can solve for spring rate by determining how much compression you want to start with.

Sean
 

Sal R.

Active member
I do agree that my suspension is probably stiffer in the front that what it should be. It helps keep the truck stable (not running a sway bar currently), but it's pretty harsh on washboard. Small and abrupt bumps/variances in paved roads can be very harsh also. What I don't fully understand is how swapping to a lower spring rate will affect my ride height. If I drop to a longer 650 lbs spring, will I be able to keep my ride height? Or will the front drop? I need to keep the front of the truck where it is for the trails in my area. Some of them have deep ruts that would have me scraping my underside or high centering if I loose my clearance in the front. I believe I'm running a 14" 700 lbs spring at the moment, with 1.00-1.25" preload.
Sounds to me like you need adjustable shocks.

What's good on the street will be harsh on the trails.

What's good on the trails will be soft on the street.

Precisely the reason I have adjustability on all four corners on my DD.
 
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toyotech

Expedition Leader
Sounds to me like you need adjustable shocks.

What's good on the street will be harsh on the trails.

What's good on the trails will be soft on the street.

Precisely the reason I have adjustability on all four corners on my DD.
I agree. My fox with DSC rides great on street and trail. No stiff or harsh ride


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Kpack

Adventurer
Sounds to me like you need adjustable shocks.

What's good on the street will be harsh on the trails.

What's good on the trails will be soft on the street.

Precisely the reason I have adjustability on all four corners on my DD.
That's what I've been thinking. I'll have to work with what I have for a bit though. Budget is going elsewhere at the moment. For front adjustable coilovers I'm looking close to $2K or higher.

The truck is my daily driver so I need it to do a bit of everything. Most of its time is spent on the road, with wheeling adventures happening on the weekends during the season. As such I know there will be many compromises.
 
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