Bilstein setting with lift coil

[LJ75 Driver]

Ok... been searching for a while. I'm sitting in my shop looking at this pile of parts, I'm done pulling the Dobinson set up off the truck.
I 'acquired' a 5100 set up in putting on to lower the truck down a bit. My brother in law gave me a full 5100 set up and SAW 1.5" rears.
My question becomes, if I used my Dobinson 2" front springs on the 5100's, why do they have to be at the lowest setting? Ideally I'd like to use the .85" setting with the 2" spring.
Can the clip not handle the pressure? I find that a little hard to believe but that's the only conclusion I can come to. I don't want to max out the 5100's, I'd like better range of motion, less preload, that's why the Dobinson long travel is coming off. Long travel is great, but you also need some down travel! Lol
I've been doing suspension most of my life, but this T4R is killing me. My wife loves it, but I'm starting to miss solid axles, badly.
This is the last attempt at a suspension that works correctly before it goes solid axle.
On the flip side. I have a complete Dobinson long travel system for sale!

 

[MeefZah]

My question becomes, if I used my Dobinson 2" front springs on the 5100's, why do they have to be at the lowest setting? Ideally I'd like to use the .85" setting with the 2" spring.
Can the clip not handle the pressure?

The consensus seems to be that it's not an issue of the clip "handling the pressure" at all. From a mechanical standpoint it should be fine. I don't see why you couldn't use the 2nd notch in conjunction with the 2" coils, just expect the ride to suffer a little.

 

[TEujunga]

When the suspension is loaded with the weight of the truck, the amount of pressure on the clip will be the same no matter what position you use. That's why the truck sits at different heights depending on the clip position. The height of the spring under load remains the same.

 

[LJ75 Driver]

When the suspension is loaded with the weight of the truck, the amount of pressure on the clip will be the same no matter what position you use. That's why the truck sits at different heights depending on the clip position. The height of the spring under load remains the same.

No... when you move the clip up you're preloading the spring, higher clip, more squeeze on the spring. That's WHY it lifts the truck. Springs are rated in pounds per inch, and have a load rating. It takes for instance 300# to squeeze it an inch. It takes another 300 (600 total) to squeeze it another inch, and so on... However, there is a load rate of how much a spring is designed to carry at a certain compression which just complicates things.
I'm at a loss for how bilstein says you're not preloading the spring... that's exactly what happens if you move the seat up and not the top hat.

Anyway... has anyone come up with a good reason why you shouldn't use a higher clip setting with a lift spring? Toytec and bilstein were no help. One didn't answer, the other said 'cus it's designed that way'. I said ok, what will happen?
'Well we don't really know, we never tried it'...

 

[TEujunga]

No... when you move the clip up you're preloading the spring, higher clip, more squeeze on the spring. That's WHY it lifts the truck. Springs are rated in pounds per inch, and have a load rating. It takes for instance 300# to squeeze it an inch. It takes another 300 (600 total) to squeeze it another inch, and so on... However, there is a load rate of how much a spring is designed to carry at a certain compression which just complicates things.
I'm at a loss for how bilstein says you're not preloading the spring... that's exactly what happens if you move the seat up and not the top hat.

Not to belabor the point, but perhaps this will prevent someone else reading this thread from perpetuating the same misconception.

"Preload" is a myth -- at least, in an application like the T4R with constant-rate springs. Yes, the spring must be compressed to fit inside the top hat, and the amount of compression needed for assembly is greater when the bottom of the spring is moved up, as with a higher setting on a Bilstein 5100.

However, once the weight of the truck is resting on the spring, it will be compressed exactly the same amount no matter where the bottom of the spring was placed in the coilover. With a higher spring position, the amount of rebound travel is reduced, and the ride height is raised, but the spring rate remains the same. Therefore, if there's 1,150 lbs. resting on the spring, it will be compressed to the exactly same height no matter how much "preload" you had to put on it to get it into the top hat for assembly.

I realize this seems counter-intuitive, but forget for a moment about the coilover assembly process and simply visualize the spring in its compressed state with the weight of the vehicle on it. You will see that changing the location of the bottom spring perch is what changes the ride height of the truck, and that it has nothing to do with either a change in spring rate due to "preload" or the spring's final compressed height, both of which remain constant.

 

[JKLNHYD]

I have long thought about this same question. I have 3" lift coils and considered setting my 5100's on the .85" setting. I'd imagine it becomes an alignment and CV angle factor before anything else. Which in turn would require set of UCA's. But just as you have already mentioned, the more you compress the coil, the more "drop travel" you lose.

 

[mccamp82]

Not to belabor the point, but perhaps this will prevent someone else reading this thread from perpetuating the same misconception.

"Preload" is a myth -- at least, in an application like the T4R with constant-rate springs. Yes, the spring must be compressed to fit inside the top hat, and the amount of compression needed for assembly is greater when the bottom of the spring is moved up, as with a higher setting on a Bilstein 5100.

However, once the weight of the truck is resting on the spring, it will be compressed exactly the same amount no matter where the bottom of the spring was placed in the coilover. With a higher spring position, the amount of rebound travel is reduced, and the ride height is raised, but the spring rate remains the same. Therefore, if there's 1,150 lbs. resting on the spring, it will be compressed to the exactly same height no matter how much "preload" you had to put on it to get it into the top hat for assembly.

I realize this seems counter-intuitive, but forget for a moment about the coilover assembly process and simply visualize the spring in its compressed state with the weight of the vehicle on it. You will see that changing the location of the bottom spring perch is what changes the ride height of the truck, and that it has nothing to do with either a change in spring rate due to "preload" or the spring's final compressed height, both of which remain constant.

Agreed.....great explanation.

My hunch/belief is that there is no reason you can't use a lift coil in combination with a higher spring perch. New UCAs, diff drop, etc would be a must, and your droop would be reduced. You might also need new lower bump-stops to keep the shock from over-extending.

One other thing to note is that I believe the .85" setting on the 5100s is actually about 1" to 1.25". Someone please correct me if I'm wrong.

Good luck if you decide to go this route and love to see/hear about the results.

 

[BLACK-FL4RUNNER]

If you raise the spring seat (past the first notch) and use a 2" lift coil, your strut won't last very long. You are adding alot more stress when at full extension of the assembly. The 5100's are only designed for a max of 2.5" lift, you will be simulating a 2" + .85" for a total of 2.85" lift. Will it hurt it? Maybe, maybe not. It's just going to be topping out with much greater force then designed.

 

[mccamp82]

If you raise the spring seat (past the first notch) and use a 2" lift coil, your strut won't last very long. You are adding alot more stress when at full extension of the assembly. The 5100's are only designed for a max of 2.5" lift, you will be simulating a 2" + .85" for a total of 2.85" lift. Will it hurt it? Maybe, maybe not. It's just going to be topping out with much greater force then designed.

The 5100s provide a max of 2.5" lift, but they can definitely accommodate at least 3" of lift. One example: the Toytec Ultimate coilovers use 5100s and are 3" lift. I believe many people use these shocks with 3" lifts with no problem. But will definitely make it have less droop and the shock will potentially have more stress when at full extension, like you mentioned.

 

[BLACK-FL4RUNNER]

They provide a 2.5" coil lift, and a 1/2" top plate spacer lift, to accomplish that 3" total lift.

Over 2.5" of lift with using coil only, you will probably be over extending the strut on normal driving. That will cause premature failure, and will provide less flex for off road travel.

 

[BLACK-FL4RUNNER]

The bilstein 5100 only has about 4.9" of movement, which equals about 10" of wheel flex. (2 to 1 ratio).

Under normal operation, let's assume the strut is in the middle with 2.4" of up travel and 2.4" of down travel for movement. Raising the truck with 2" coil and .85" lower spring bucket, will bring you to 2.85" lift. Using that 2 to 1 ratio means you extended the strut another 1.4" past the middle. That means you only have about 1" of strut downtravel. That's not good, you will be extending the strut causing premature failure, a shitty ride, and less flex for offroad. Hope my explanation makes sense, I'm not really good at explaining things.

 

[mccamp82]

The bilstein 5100 only has about 4.9" of movement, which equals about 10" of wheel flex. (2 to 1 ratio).

Under normal operation, let's assume the strut is in the middle with 2.4" of up travel and 2.4" of down travel for movement. Raising the truck with 2" coil and .85" lower spring bucket, will bring you to 2.85" lift. Using that 2 to 1 ratio means you extended the strut another 1.4" past the middle. That means you only have about 1" of strut downtravel. That's not good, you will be extending the strut causing premature failure, a shitty ride, and less flex for offroad. Hope my explanation makes sense, I'm not really good at explaining things.

That’s a great explanation and I don’t disagree at all.

 

[LJ75 Driver]

That’s a great explanation and I don’t disagree at all.

Same here...
I ended up just using the bottom setting with the Dobinson springs. So far so good, I'll finish putting the front end back together in the morning. I buggered the threads on the driver side lower strut bolt somehow removing it, and no one in Houston has one. Has to come from Dallas.

As far as preload being a myth, I have to disagree. All you explained was load rating. How much a spring will carry at certain compression. Which you hit spot on, I'll admit. But I'm not one to argue, it's not worth typing more explanations.
Thank y'all for the help.