All lifts are created equal?

[DragonRunner]

Thanks to [MENTION=306890]MAST4R[/MENTION] for an earlier reply. Thought I’d reach out for more opinions...

I don’t know how many threads I’ve read here and on 4Runner and Tundras regarding lifts, but it’s more than a few. I see spacer lifts (above and below the hat), shock preload (Bilstein 5100, etc) and coil lifts. I’m trying to figure out how to minimize the impact to ride quality (harshness) with the type of lift. Besides the effect spacers have on travel length / droop / coil pinch, it appears that a spacer lift does the same thing that a shock lift would do at an other than 0 setting - preload the coil. Is that right? If I dial in a 5100 to the top perch, am I just adding max preload and therefor gaining height but loosing ride comfort? There are so many recommendations to buy a new coil/spring to effect the lift and set say my 6112 on “0” to remove preload and “let the coil lift the truck,” but someone I found creditable said that’s basically the same thing! You’re just buying a coil with a “preload” over a factory coil built in. That the only way to lift via coil is to increase coil length, but that requires more complexity with new LCA / UCA / Spindle changes, etc. All this comes to a point as I just purchased a 6112/5160 set and in an effort to avoid setting the shock to a 3 or 5 clip perch for the lift and making the ride more harsh, I wanted to swap out the coil the 6112 comes with for another one that provides the lift. All I could find was talk of heavier springs... 650lbs, 700lbs, etc. Is this the juxtaposition where the mantra “let the coil lift the truck, set the shock to 0” equals the same stiff ride as a stock coil around a 5100 maxed out? Is there no “longer” coil at a 550lb rate that lifts the truck?

My head hurts...

 

[Jetboy]

Springs should be linear within the range that you use them (unless you get some progressive rate coils...) For this purpose assume that's true that they are linear.

So then there are a few basic facts about the system.

1: For every inch of compression a 550lb spring adds another 550lb of force. That' doesn't matter if it's the first inch of compression or the last.
2: Travel is limited by the bump stop one one end and the shock extension limit on the down travel end. (If not - you have bigger issues you need to sort out).

Given those two facts, the result is that for a given spring rate - it doesn't make any difference at all whether you set your ride height by adjusting the spring mounts or by choosing a longer or shorter spring (with the same spring rate). When you put the weight of the vehicle on the spring it will come to rest with exactly the same spring load and have exactly the same properties throughout the range of motion. So... if your ride height is the same and the spring rate is the same between various spring lengths, how you get there makes no difference.

Where preload becomes meaningful is when you start playing with spring rates. You do not want the coil spring to reach zero load before or even at the end of its travel on the IFS of these vehicles. What that means is that you do in fact want some preload. What that really means is that you want the spring to be partially compressed even when the shock reaches its maximum extension. So that means that you should be using a coil spring rate that will carry the full weight of the vehicle in the middle of the shock extension range, have enough compression range not to "brick" where the coils hit eachother on compression, and also have a light enough spring rate not to reach full extension. There's a range of spring rates that do that based on the load you're carrying. Typically in a 4Runner that is somewhere between 500 and 700lb per inch.

Personally I would choose the softest spring that can carry the weight and not brick at full compression. I'll skip the full details - but the short version is it will give you better traction and a better ride. The shock absorber is the correct mechanism to keep you from bottoming out. So you would then want to tune the shocks to work well with the springs you've chosen. The two components need to work together and have a balance for the best performance.

So... the result is this: use the springs that came with the 6112 shocks. Longer springs of the same rate make zero difference and will simply be a waste of money and effort. And I mean that literally - there will be no difference whatsoever in function. If you need a heavier or softer spring set, then start looking for other spring options to carry more or less weight.

good luck

 

[mscot]

so, if I'm reading that right. a stock weight T4R with a 650lb spring and 2.75" lift will drive the same as a T4R with 120lbs on the front end and the same 650lb springs but a resulting 2.25" lift?

is that right?

 

[Jetboy]

so, if I'm reading that right. a stock weight T4R with a 650lb spring and 2.75" lift will drive the same as a T4R with 120lbs on the front end and the same 650lb springs but a resulting 2.25" lift?

is that right?

No. Not exactly. What I'm saying is essentially if you put a 14" 650lb spring set on one and a 12" 650lb spring set on another that both have the same weight and you set the spring perch on the 12" spring and 14" spring to have the same initial ride height - the two will ride identically.

In the case of same spring rate but different weights, then the two will ride differently.

Similarly, with the same weight and shock valving, a 550lb spring rate will ride differently from a 650 lb spring rate.

 

[DragonRunner]

No. Not exactly. What I'm saying is essentially if you put a 14" 650lb spring set on one and a 12" 650lb spring set on another that both have the same weight and you set the spring perch on the 12" spring and 14" spring to have the same initial ride height - the two will ride identically.

First thank you for the detailed explanation. Can you go further into why folks recommend getting a coil to give you the lift so the shock can be set to “0,” which I assumed meant longer coils and no additional preload from the shock? I’m thinking coilovers and adjustables (5100/6112) accomplish the same thing in essence - just with different fine tuning of ride height - which is to shift the coil perch up thus increasing ride height but reducing down travel, but does that add preloading too? Or do only spacers do that?

 

[IrieRider]

Keep in mind a spacer height and lift height will be different. I know in my past with IFS vehicles this can add some confusion for people.

 

[Jetboy]

First thank you for the detailed explanation. Can you go further into why folks recommend getting a coil to give you the lift so the shock can be set to “0,” which I assumed meant longer coils and no additional preload from the shock? I’m thinking coilovers and adjustables (5100/6112) accomplish the same thing in essence - just with different fine tuning of ride height - which is to shift the coil perch up thus increasing ride height but reducing down travel, but does that add preloading too? Or do only spacers do that?

Adding a top spacer withing the spring area or a longer spring or moving the lower spring perch all have the same effect. (always with the caveat that you're not bricking the spring). If you set it up in such a way that the spring will fully compress before the bump stop stops the compression motion - usually you'll break the lower shock mount off. That can be from either a lower mount that's set too high, to thick of top spacer, or a spring too long for the application. This is why we can't use a 400lb spring rate. The spring with a 400lb rate would have such a long uncompressed length that it would end up fully compressing to the point that the coils hit eachother (bricked) before full compression of the suspension.

Like this:

You can have the same result also by letting the shock inside the coil spring fully bottom out.

Adding the spacer above the top had creates this risk. It also does a few other things. The top spacer generally will keep the same performance in the overlapping range of travel, but the range of motion then changes - so it will have more down travel and less up travel. If the limit on up travel is the bump stop - then there's some benefit because you have more down travel with the same up travel. However - if the shock bottoms out first... then you break the shock. That's not totally uncommon. My guess is lifts like Toytec figure out the compressed length and then use a top spacer that still lets the bump stop limit compression without ever either fully bottoming out the shock or fully bottoming out the spring. The use of spacers on both sides of the top hat is probably necessary to use the OEM spring and shock and still get a 3" lift without breaking anything. It's not really an ideal solution, but it's very inexpensive to manufacture. I'd guess I could get those spacers cut for maybe $10 for the set of 4. If there's some wiggle room with the OEM setup, you might get a slight benefit there.



There is some slight difference in the internal pressure as the shock compresses. So the spacer outside of the top had that changes the extension of the shock at static ride height will have some minor change in shock performance. It should be very limited on most shocks - especially those with smaller shafts and lower internal pressure. The primary function of a remote reservoir is to manage that pressure change due to the volume taken up by the shock shaft as the shock compresses. In most RR shocks the difference is almost nothing. The same is likely true for most twin tube shocks (the outer tube is basically a remote reservoir). The monotube non-reservoir shocks with limited volume of compressed gas above the floating piston are probably most affected by this. So the 5100 is going to probably see a bit more. But again - I don't think the difference is enough that it's going to have any meaningful effect on ride quality. The piston flow through the oil is the primary dampening, the internal pressure - even if it's 500psi would only put maybe 100lb of force on the shock shaft, and that's at full compression where the spring is probably applying something like 1500lb of force.


One final thought is that you can also break a shock by having it ride very close to full extension. The shocks are designed to act as the limiter for down travel. However, if you set up the suspension where the shock is hitting full extension just beyond normal ride height - then on something like a washboard road, it's experiencing repeated hammering against the piston and the bumper internally. That usually results in breaking the piston off of the shaft internally. Some people have learned the hard way on that one too. That's what happens when you run these at 4" of lift with shocks that only give you 1" of down travel and try to use them in the dirt. Especially with lighter duty shocks. Shocks like the Fox 2.5 have big thick rubber bumpers inside and very heavily built shafts and pistons that can handle that type of abuse. Something like a 5100 does not. OEM shocks absolutely can't handle it. And regardless of shock type - the ride quality is horrible if you set it up that way. The only time you'd want to ride on the maximum possible height is somewhere that you otherwise would be dragging the belly, deep water, or similar and when you'll be going really slowly. Otherwise - it's best to setup the suspension where you have a good remaining amount of down travel available for a nice ride.

 

[jrm]

I had my set @ 4 / 6

Thanks to [MENTION=306890]MAST4R[/MENTION] for an earlier reply. Thought I’d reach out for more opinions...

I don’t know how many threads I’ve read here and on 4Runner and Tundras regarding lifts, but it’s more than a few. I see spacer lifts (above and below the hat), shock preload (Bilstein 5100, etc) and coil lifts. I’m trying to figure out how to minimize the impact to ride quality (harshness) with the type of lift. Besides the effect spacers have on travel length / droop / coil pinch, it appears that a spacer lift does the same thing that a shock lift would do at an other than 0 setting - preload the coil. Is that right? If I dial in a 5100 to the top perch, am I just adding max preload and therefor gaining height but loosing ride comfort? There are so many recommendations to buy a new coil/spring to effect the lift and set say my 6112 on “0” to remove preload and “let the coil lift the truck,” but someone I found creditable said that’s basically the same thing! You’re just buying a coil with a “preload” over a factory coil built in. That the only way to lift via coil is to increase coil length, but that requires more complexity with new LCA / UCA / Spindle changes, etc. All this comes to a point as I just purchased a 6112/5160 set and in an effort to avoid setting the shock to a 3 or 5 clip perch for the lift and making the ride more harsh, I wanted to swap out the coil the 6112 comes with for another one that provides the lift. All I could find was talk of heavier springs... 650lbs, 700lbs, etc. Is this the juxtaposition where the mantra “let the coil lift the truck, set the shock to 0” equals the same stiff ride as a stock coil around a 5100 maxed out? Is there no “longer” coil at a 550lb rate that lifts the truck?

My head hurts...

providing 2.51" of lift and the ride suffered in harshness and the frequency of the rebound and compression due to preload. Changed it to 3/5 @ 2.14"s and the ride improved greatly. Not to mention the mpg improved as well. the improved damping of the 2.5" 6112 with the 650lbs OE coil is noticeably better than the 5100 combined with the ome 883 set @ 0

 

[DragonRunner]

providing 2.51" of lift and the ride suffered in harshness and the frequency of the rebound and compression due to preload. Changed it to 3/5 @ 2.14"s and the ride improved greatly. Not to mention the mpg improved as well. the improved damping of the 2.5" 6112 with the 650lbs OE coil is noticeably better than the 5100 combined with the ome 883 set @ 0

Thanks for this real-world feedback. Imagine in it was a PIA to go back in and reset the c-clip in a “troubleshooting” kinda way, so this saves me hopefully from the same.

Is the shock actually producing different levels of preload? I though the coil spring seat moving up (like to perch 7) just moved the truck up and reduced the down travel available, leading to potentially more frequent full extentions. Is that what you mean by a harsher ride? I used to think maxing a 5100 or 6112 in lift height meant a “stiffer” ride due to squeezing the coil but I don’t think that’s how it works.

 

[mscot]

[MENTION=118321]Jetboy[/MENTION] I have a question for you.

I just put the Eibach suspension on and left it at the lowest perch. Due to bumper/winch weight I only got ~1.5" lift instead of the 2.75" it should see at stock weight.
Eibach suggested moving it up to the second perch to accommodate for the spring compression.

My thoughts are, this will give me more height but it will not give me more travel than what I have now.
The compressed springs are what is limiting my travel, not how high my lift is, and that wouldn't change just by moving it to a higher perch.
Is that correct?

 

[Jetboy]

[MENTION=118321]Jetboy[/MENTION] I have a question for you.

I just put the Eibach suspension on and left it at the lowest perch. Due to bumper/winch weight I only got ~1.5" lift instead of the 2.75" it should see at stock weight.
Eibach suggested moving it up to the second perch to accommodate for the spring compression.

My thoughts are, this will give me more height but it will not give me more travel than what I have now.
The compressed springs are what is limiting my travel, not how high my lift is, and that wouldn't change just by moving it to a higher perch.
Is that correct?

Moving the spring perch up will not change the travel at all. The limit on the down travel is the shock reaching it's full length. The limit on the up travel is the bump stop. So the suspension will move through the same total range from top to bottom regardless of where the perch is set. Moving the perch up will change where in that range of motion your 4Runner sits at normal ride height. So if you want it to sit higher - then you would want to move the spring perch up a bit.

 

[Bergz]

Damn Jetboy....

Great stuff!! Thanks for the knowledge drop!

 

[mscot]

Moving the spring perch up will not change the travel at all. The limit on the down travel is the shock reaching it's full length. The limit on the up travel is the bump stop. So the suspension will move through the same total range from top to bottom regardless of where the perch is set. Moving the perch up will change where in that range of motion your 4Runner sits at normal ride height. So if you want it to sit higher - then you would want to move the spring perch up a bit.

Thanks for this.
So, in reality, as long as I can get it to stop rubbing, there's no reason to spend the time (or money) to pull the shocks off and move them up a notch.
In fact, the truck probably handles better at this lower setting.

 

[Jetboy]

Yep. I think you've got it right. If it rubs now - it'll also rub at a higher setting when you compress the spring a bit. Usually the ride is better at a lower height. Mine is significantly better at 1-1.5" lift than it is at 3" lift. The biggest benefit to a higher lift is more static clearance. If you're going through terrain where the underside is getting hung up, being taller can help you keep from getting stuck on rocks and such. So there's a case to be made for having a taller lift if that's an issue. If not - the lower ride height gives you a much nicer highway ride and more comfortable ride in the dirt too. It all ends up being a bit of a balance for whatever you do most.

In a perfect world, we'd have something like the LX570's system that can go up and down 3" on demand and also adjust spring rates on the fly and also be reliable. In the real world, I find something a bit higher than stock but not extreme is about ideal for my personal use.

 

[DragonRunner]

Yep. I think you've got it right. If it rubs now - it'll also rub at a higher setting when you compress the spring a bit. Usually the ride is better at a lower height. Mine is significantly better at 1-1.5" lift than it is at 3" lift. The biggest benefit to a higher lift is more static clearance. If you're going through terrain where the underside is getting hung up, being taller can help you keep from getting stuck on rocks and such. So there's a case to be made for having a taller lift if that's an issue. If not - the lower ride height gives you a much nicer highway ride and more comfortable ride in the dirt too. It all ends up being a bit of a balance for whatever you do most.

In a perfect world, we'd have something like the LX570's system that can go up and down 3" on demand and also adjust spring rates on the fly and also be reliable. In the real world, I find something a bit higher than stock but not extreme is about ideal for my personal use.

[MENTION=118321]Jetboy[/MENTION] thanks for this. This helps sum up some of what I've been bouncing around...

1 - travel isn't affected when talking total compression and droop for a spacer or c-clip style perch lift - provided the bump stop engages before spring bricks.
2 - however, since static or normal ride height IS affected, droop and/or compression travel IS affected when talking about the neutral point, or rather "I have less down travel after my 2" 6112 perch lift because 2" more of the shock is extended at static ride height." Total travel from droop-bump not affected, total travel from static height to bump, or from static height to shock limit is reduced
3 - this thought that (for IFS) a lift doesn't "fit" bigger tires is true in one sense: that if the tire rubs at stock height it will rub post lift too, but only when compressed to stock height again due to terrain. However in another sense it does allow bigger tires to fit than at stock height since the majority of the time that our suspension would be compressed down to stock height the wheels will be fairly neutral, where the least chance of rub/contact exists. Probably just semantics.

Couple more Qs:
-- the shock is the down travel limit, right? No bump-stop for this? Shocks are designed for this kind of abuse? Am I doing it wrong if I lift with a 6112 and because of that, hit the shock extension limit more frequently?
-- why (if true) is the ride harsher with a 6112 (or 5100, etc) raised up (c-clip/perch on say 5 or 6) if the spring isn't compressed more (just shifted up)? The shock is extended more, the control arms are shifted down a bit, the CV angles are slightly different, but a harsher ride? I believe this is true, but am unsure why (thus my earlier question above about trying to set the clip at 0 and finding a coil to do the lifting).

No JOKE about the 570s (470s too right?)! My buddy has one and its fantastic. Didn't know they could also adjust spring rate. How?

 

[DragonRunner]

[MENTION=107928]hishaun84[/MENTION]

 

[Jetboy]

[MENTION=118321]Jetboy[/MENTION] thanks for this. This helps sum up some of what I've been bouncing around...

1 - travel isn't affected when talking total compression and droop for a spacer or c-clip style perch lift - provided the bump stop engages before spring bricks.
2 - however, since static or normal ride height IS affected, droop and/or compression travel IS affected when talking about the neutral point, or rather "I have less down travel after my 2" 6112 perch lift because 2" more of the shock is extended at static ride height." Total travel from droop-bump not affected, total travel from static height to bump, or from static height to shock limit is reduced
3 - this thought that (for IFS) a lift doesn't "fit" bigger tires is true in one sense: that if the tire rubs at stock height it will rub post lift too, but only when compressed to stock height again due to terrain. However in another sense it does allow bigger tires to fit than at stock height since the majority of the time that our suspension would be compressed down to stock height the wheels will be fairly neutral, where the least chance of rub/contact exists. Probably just semantics.

Couple more Qs:
-- the shock is the down travel limit, right? No bump-stop for this? Shocks are designed for this kind of abuse? Am I doing it wrong if I lift with a 6112 and because of that, hit the shock extension limit more frequently?
-- why (if true) is the ride harsher with a 6112 (or 5100, etc) raised up (c-clip/perch on say 5 or 6) if the spring isn't compressed more (just shifted up)? The shock is extended more, the control arms are shifted down a bit, the CV angles are slightly different, but a harsher ride? I believe this is true, but am unsure why (thus my earlier question above about trying to set the clip at 0 and finding a coil to do the lifting).

No JOKE about the 570s (470s too right?)! My buddy has one and its fantastic. Didn't know they could also adjust spring rate. How?

The harshness comes mostly from the angles of the suspension. The easiest way to explain it is to imagine your control arms being perfectly level (they can't actually both be level, but ignore that). If they're set at a level starting spot - the typical road bump would transfer most of the impact to the spring/shock assembly.

Compare that scenario to the extreme where the control arms are totally vertical. (also not really possible, but helps for this explanation) In that scenario 100% of all of the impact of road bumps would transfer straight through to the frame and none would be absorbed by the shock/spring.

So what happens when you lift is a situation somewhere in between. I'd guess a 3" lift in front puts the control arm angles somewhere in the range of 15-20 degrees. The result is that some greater portion of every road imperfection gets transferred directly through the control arms to the frame and results in a harsher ride. There is also a greater lateral shift as the arm acs through it's range of motion the higher you go.

The same happens in the rear, but the arms are a bit longer so it's less noticeable. However - the rear panhard bar starts to cause poor ride quality by 3" lift also. A longer panhard bar doesn't solve the geometry problem. The adjusted bracket height is what really helps.

Anyway - that's the idea.

The LX adjusts spring rate by use of hydraulic valves that add or remove air springs from the system. It's complex, but the basic idea is that the shocks have hydraulic pressure that both is the shock fluid but also transfers the spring force to the shock. And there's about a dozen air chambers in the system with different spring rates (air volume to fluid ratio). And the system can change pressure by pump, but also add or remove various chambers depending on conditions.

Functionally I'm sure it's great. But I'd really hate to have to fix it if something goes wrong. Like KDSS x 100.

 

[DragonRunner]

[MENTION=118321]Jetboy[/MENTION] thank you again. Really nice explanation. I was having a hard time with that thinking solely about the coil and shock, and not the control arm angles.

 

[Jen1999]

A lot of helpful info in this thread!

 

[DragonRunner]

[MENTION=118321]Jetboy[/MENTION] [MENTION=306890]MAST4R[/MENTION]

Is there a good reason to keep the OEM top plate etc versus buying the KYB top plate like this?

I’m thinking the OEM bushings, etc are a better quality? Ideally I’d like to give the 6112 shock/coil to pep boys to assemble (for $20) then all I have to do is pop out the OEM assembly and insert the built 6112, removing the trip to pep boys in the middle of the job and allowing me to do one side at a time for references.