Please Read: Bilstein 5100 - Preload/Harshenss Explanation

[MTD]

This is interesting and both schools of thought are correct for different situations. The only time you will increase preload is if the shock absorber is topped out and cannot extend any further (this has been mentioned briefly), thus limiting the distance between the top plate and the perch.

If there is still room for the shock to extend with the perch used, the overall length of the whole assembly will simply increase instead of adding to the preload of the shock, thus leaving the weight of the vehicle as the only source of preload.

It is like the difference between the two types of spacer lifts. a coil spacer will usually achieve the top out of the shock and so preload the coil. A top plate spacer does not preload the coil, but merely extends the length of the strut. The 5100's simply do this at the other end of the strut.

That being said, if you use a long enough coil with the 5100's to achieve top out of the shock on the perch you are using, you will begin to preload the coil and that preload will increase with every perch you move up.

It is all about whether or not you top out the shock. Of course, lifting also changes suspension geometry and can ruin the ride as well, which is often incorrectly attributed to preloading the coil, but is simply a part of lifting a vehicle.

Just my .02

This was part of the point that I made during or PM discussion. Basically the my thought on it was that the spring rate stays constant as OP says, but when you add preload to the spring your are moving up the spring curve and esentaily setting a new y intercept for that curve. It is a simple linear relationship and the weight of the vehicle does not remove the preload, but instead it has less effect on how much the spring compresses because it is already compressed, thus lifting the vehicle. The harshness from the ride is due to the change in suspension geometry

 

[MTD]

Its still called preload. When did preload become a 4 letter word?

From a quick Google search.

Coilover Spring Preload Explained | ZoomSquared

EDIT: Should have read the entire thread prior to posting a reply..

Installing a strut and putting the vehicle weight on it does not negate the fact you preloaded the spring.

It seems that there is confusion with definations, but op's original post is not correct (nothing personal). But adjusting the coil pressure on a set shock absolutely is adjusting preload. It doesnt matter if the coilover is on or off the vehicle, the end result is the same. Adjusting the coil on a coilover is relative to the shock. Whether you adjust the preload before of after installing the coilover on your front end makes no difference.

This guy illustrates everything in a real life example using hookes theory. Lift is achieved by adjusting the preload on a coilover, which absolutely will make the vehicle ride stiffer.

Coilover Spring Preload Explained | ZoomSquared

Edit: I have to take part of that back . . . op you are correct about spring rate not changing. Had to re-read that. However adjusting the coil is adding preload by defination, and that is how lift is achieved. But the stiffer ride must be a result of other factors like changing a arm angles and such as mentioned, not spring rate

^^^^That was the point I was trying to explain all last night lol but at 1 in the morning after as many pots of coffee I had it just was not coming out....

 

[Brilliant]

Why would it not apply to OE coils?

non-linear springs are just that, non-liner. OE springs are some function of x

F=f(x) whereas F=-kx for linear springs and f(x) for nonlinear is some power function. ie F=Ax^b

Since we're dealing with OE stiffness, a nonlinear spring this is dF/df(x). So K for nonlinear springs is a function of displacement itself, ie K = Ax^-b

someone can check that, i am running out the door.

 

[Dezert4Runner]

non-linear springs are just that, non-liner. OE springs are some function of x

F=f(x) whereas F=-kx for linear springs and f(x) for nonlinear is some power function. ie F=Ax^b

Since we're dealing with OE stiffness, a nonlinear spring this is dF/df(x). So K for nonlinear springs is a function of displacement itself, ie K = Ax^-b

someone can check that, i am running out the door.

Unless you're using Tundra TRD or Tacoma TRD coils, all factory 3rd gen front coils are linear, not progressive. This includes all aftermarket coils (ie: Eibachs, OME, etc). Let's not mix up our facts here. We are talking about a linear coil spring in regards to preload.

As you were...

 

[1985taylor1925]

Unless you're using Tundra TRD or Tacoma TRD coils, all factory 3rd gen front coils are linear, not progressive. This includes all aftermarket coils (ie: Eibachs, OME, etc). Let's not mix up our facts here. We are talking about a linear coil spring in regards to preload.

As you were...

Thats what I was thinking. I said that all coils are technically progressive, but I just meant that you need to progressively add force to further compress them. I.e. 500lbs to compress 1", 1000lbs to compress 2", etc. Still creates a linear graph. I dont think the 3rd gen 4runner ever had an oem progressive coil right?

 

[Dezert4Runner]

I dont think the 3rd gen 4runner ever had an oem progressive coil right?

Nope

 

[vincer77]

I think we're using the wrong Hooke's EQN. Another form of Hooke's Law uses the concept of work and is:

work = (.5K)(x^2)

This illustrates how X effects work exponentially and is not linear.

The x in this term is the displacement from the initial condition. A coil that has been preloaded by an amount x1 and is just sitting, is not "working" To further displace it to X2 requires work. The work is given by your equation where x = x2 - x1.

 

[Brilliant]

Unless you're using Tundra TRD or Tacoma TRD coils, all factory 3rd gen front coils are linear, not progressive. This includes all aftermarket coils (ie: Eibachs, OME, etc). Let's not mix up our facts here. We are talking about a linear coil spring in regards to preload.

As you were...

I doubt oe 4runner coils are linear, but they could be nearly linear. From what I saw, the complaints are for preloading tundra coils with the 5100s and why I asked about the assumptions. And of course AM coils are linear. That should be apparent.

It should also be apparent that preload has no effect on spring rate on a linear spring. Preload affects droop and bump though.

Assume a 2000lb vehicle with 500lb rate springs x4. With no preload the vehicle will be set down off the stands will compress the springs 1".

With 1" preload, the same vehicle will not deflect the spring any amount when set down from the stands. This is because each spring has 500lb restoring force already in each coil (x4).

all preload, a mix of preload and vehicle weight, or zero preload the springs will end up compressing the same amount.

droop and bump will affect ride quality, though not related to spring stiffness.

 

[Dezert4Runner]

I doubt oe 4runner coils are linear, but they could be nearly linear. From what I saw, the complaints are for preloading tundra coils with the 5100s and why I asked about the assumptions. And of course AM coils are linear. That should be apparent.

It should also be apparent that preload has no effect on spring rate on a linear spring. Preload affects droop and bump though.

Assume a 2000lb vehicle with 500lb rate springs x4. With no preload the vehicle will be set down off the stands will compress the springs 1".

With 1" preload, the same vehicle will not deflect the spring any amount when set down from the stands. This is because each spring has 500lb restoring force already in each coil (x4).

all preload, a mix of preload and vehicle weight, or zero preload the springs will end up compressing the same amount.

droop and bump will affect ride quality, though not related to spring stiffness.

Logic tells me a progressive spring that gets preloaded more than stock height would compress into the stiff portion at ride height, so I'd think it would only make sense to run if you planned on keeping it at the ~2" the Tundra TRD coil gives you without moving up notches on the 5100's. I never understood why people with Tundra TRD coils liked them when used on anything other than the bottom notch or maybe 2nd notch, unless they had plate bumper/ skids. I think it's like [MENTION=78060]The4kbeast[/MENTION] mentioned in his build thread about small bump compliance not being comfortable/ ideal.

I ran Taco 5100's on my 01 DC Tacoma TRD (came with stock Tacoma TRD progressive springs, which I used) on the 2.5" setting (top notch) and it rode stiff. I have the same shocks on my 4Runner but with 99 tall coils (linear rate coils) set at the middle notch giving me 2.5" lift, and the ride is so much better it's note even close! Is it the difference in which 5100 notch I used or the progressive spring vs the linear rate spring? I'm inclined to believe it's the coils, personally. I remember everyone on TTORA saying don't run the TRD Taco springs with 5100's for this exact reason; because they didn't mesh as well as the non TRD Tacoma coils.

Oh, and I agree with the rest of the above quote!

 

[1985taylor1925]

Logic tells me a progressive spring that gets preloaded more than stock height would compress into the stiff portion at ride height, so I'd think it would only make sense to run if you planned on keeping it at the ~2" the Tundra TRD coil gives you without moving up notches on the 5100's. I never understood why people with Tundra TRD coils liked them when used on anything other than the bottom notch or maybe 2nd notch, unless they had plate bumper/ skids. I think it's like [MENTION=78060]The4kbeast[/MENTION] mentioned in his build thread about small bump compliance not being comfortable/ ideal.

I ran Taco 5100's on my 01 DC Tacoma TRD (came with stock Tacoma TRD progressive springs, which I used) on the 2.5" setting (top notch) and it rode stiff. I have the same shocks on my 4Runner but with 99 tall coils (linear rate coils) set at the middle notch giving me 2.5" lift, and the ride is so much better it's note even close! Is it the difference in which 5100 notch I used or the progressive spring vs the linear rate spring? I'm inclined to believe it's the coils, personally. I remember everyone on TTORA saying don't run the TRD Taco springs with 5100's for this exact reason; because they didn't mesh as well as the non TRD Tacoma coils.

Oh, and I agree with the rest of the above quote!

Hmm, thats a set up I have never considered . . . 5100s with oem coils. I have the Tudra/bilstein setup, except mine are the stock bilsteins that came on the Tundra in 06, not the 5100s. But as you mentioned, the ride is stiff, and I am positive the coils are to blame. Ive read so many people say they like the Tundra/bilstein set up. Maybe the majority of them have a front bumper. But mine is uncomfortably stiff and Ive never gotten used to it. Im thinking 5100s with 99 coils might be my next set up. Thanks for the info!

 

[The4kbeast]

Hmm, thats a set up I have never considered . . . 5100s with oem coils. I have the Tudra/bilstein setup, except mine are the stock bilsteins that came on the Tundra in 06, not the 5100s. But as you mentioned, the ride is stiff, and I am positive the coils are to blame. Ive read so many people say they like the Tundra/bilstein set up. Maybe the majority of them have a front bumper. But mine is uncomfortably stiff and Ive never gotten used to it. Im thinking 5100s with 99 coils might be my next set up. Thanks for the info!

The 4R 5100s are much better with an OEM 4R rate, IMO. At this point the only Billy setup I'd consider is 4R 5100 Billy with 99 front coils on one of lower two mounting points. The longer spring (vs 4R) with a softer overall rate (vs Tundra) is what makes this spring ideal.

If you think a heavily preloaded 4R spring rides rough, Tundra setups seem to have a harsher ride even with nearly no preload, all due to the higher spring rate and higher bump and rebound valving. The Tundra setups are probably not worth messing with for most. If you have plate bumpers with lights and winch, that's when I'd consider the Tundra gear. But even then, it's rolling the dice on how you think a lifted truck should ride and handle. That's the variable that's tough to account for. Got to tour Radflo's production facility this past week - they have different variations of tune depending on country, intended use, etc... again, a variable that is tough to quantify.

 

[1985taylor1925]

The 4R 5100s are much better with an OEM 4R rate, IMO. At this point the only Billy setup I'd consider is 4R 5100 Billy with 99 front coils on one of lower two mounting points. The longer spring (vs 4R) with a softer overall rate (vs Tundra) is what makes this spring ideal.

If you think a heavily preloaded 4R spring rides rough, Tundra setups seem to have a harsher ride even with nearly no preload, all due to the higher spring rate and higher bump and rebound valving. The Tundra setups are probably not worth messing with for most. If you have plate bumpers with lights and winch, that's when I'd consider the Tundra gear. But even then, it's rolling the dice on how you think a lifted truck should ride and handle. That's the variable that's tough to account for. Got to tour Radflo's production facility this past week - they have different variations of tune depending on country, intended use, etc... again, a variable that is tough to quantify.

Thats what Im running right now . . . stock coils and bilsteins (complete coilover) from an 06 Tundra. But in another thread we figured out awhile back that my coils are from a 4x4 4 door tundra, but are not the TRD coils and therefore not progressive. They have a different color code than the TRD coils. So this is really the reason for my ultra harsh ride. I was comparing my tundra coils to others with TRD coils not knowing that all along mine were non-progressive. Im sure the TRD coils ride nicer than mine.

I am still very interested in running the 5100s with 99 tall coils though

 

[The4kbeast]

Thats what Im running right now . . . stock coils and bilsteins (complete coilover) from an 06 Tundra. But in another thread we figured out awhile back that my coils are from a 4x4 4 door tundra, but are not the TRD coils and therefore not progressive. They have a different color code than the TRD coils. So this is really the reason for my ultra harsh ride. I was comparing my tundra coils to others with TRD coils not knowing that all along mine were non-progressive. Im sure the TRD coils ride nicer than mine.

I am still very interested in running the 5100s with 99 tall coils though

What paint code Tundra springs are you running?

 

[1985taylor1925]

What paint code Tundra springs are you running?

Red/blue red/yellow. Another member on the forum was looking at an identical set on craigslist a few weeks ago, and they came off the exact same model I got mine from . . . an 06 double cab 4x4