What is the best riding and performing lift kit for my 2001 TJ?

[Goatman]

So I guess if I take the rear seat out my Jeep still weighs the same? And then I put 6 bags of concrete back there, Still weighs the same?

Let's look at the spring a bit differently. Using airbags instead of bent steel. Still act as the springs. So if I put 75 psi in the airbags it will ride the same as when I have 250 psi in the bags? Only thing changing is the effective spring rate. So in your opinion the Jeep will ride the same at 75 and 250 psi? Same Jeep. Same shock. Same tire.
The fact is that all of them work in combination to provide ride quality. Change any of them and you change how it rides. Change the vehicle weight (yes, it does change) and you change how it rides. Change the spring rate and you change how it rides.

 

[jjvw]

So I guess if I take the rear seat out my Jeep still weighs the same? And then I put 6 bags of concrete back there, Still weighs the same?

Let's look at the spring a bit differently. Using airbags instead of bent steel. Still act as the springs. So if I put 75 psi in the airbags it will ride the same as when I have 250 psi in the bags? Only thing changing is the effective spring rate. So in your opinion the Jeep will ride the same at 75 and 250 psi? Same Jeep. Same shock. Same tire.
The fact is that all of them work in combination to provide ride quality. Change any of them and you change how it rides. Change the vehicle weight (yes, it does change) and you change how it rides. Change the spring rate and you change how it rides.

You are changing the ride height along with creating extreme scenarios outside the realm of practicality. No one is running bags in a Jeep with 250psi. And if one did so, the difference between 75 and 250psi creates a change in ride height along with a bag that does not compress.

Stick with a suspension that actually works for our application. Meaning this spring, bag, foam pillow needs to provide the desired ride height, and also offer a compressed and free length to support the desired shock travel.

 

[mrblaine]

I understand what you're saying. But unless you're getting into the bumpstops the amount of travel is irrelevant. If the spring is a half inch taller or shorter its not likely to make a niceable difference. At least for initial feel. But I will grant you that we might be into our bumpstops more often than we realize. In that case it could make a difference.

As far as tuning by spring. Lets use OME springs in our example since they offer a variety of springs. Looking only at their rear springs designed for TJ/LJ lets consider the OME941 light spring with a rate of 140lbs/in vs the OME996 rated at 250lbs. Granted these springs will offer dramatic differences in height. So we will need to make some adjustments to the light spring. (In the end we are still using a hypothetical example. But bear with me.) So lets assume the light spring has a spacer under it to provide the exact same ride height as the 996. They are both bumpstopped at exactly the same height to avoid full coil bind on the light spring. So now we have one spring rated at 140lbs and another rated at 250lbs. Both of which offer the same range of travel and both springs are readily available today from any OME dealer.

Now lets pair these two coils up with the same shock absorber and take them for a test drive. What happens when the Jeep with a pair of 250 lb coils encounters a dip in the road inducing a force of 1000lbs? (Not unreasonable if you have an LJ with a heavy bumper and tire carrier and are packed for a weekend out camping) The rear of the Jeep will drop by 2" right? (250 x2 springs = 500 lbs/in; 1000/500=2") What happens to the springs with a rate of 140lbs? (140x2 springs = 280lbs/in; 1000/280=3.57") So the Jeep with the soft coils compresses the shocks by 3.57" Nearly twice as far. Now what happens at rebound? Is it not reasonable to expect the Jeep with 250lb springs to rebound considerably faster than the soft springs exerting only 140lbs of rebound force? The firm spring has 80% more force behind it. How could it not rebound faster? Depending on the shocks valving the soft spring might rebound at half the rate of the firm spring. The soft springs will rebound like a flat basketball next to the firm springs. Not only will the firm springs rebound faster, but the lighter springs also need to rebound nearly twice the distance. So now the soft springs need to rebound nearly twice as far at half the rebound speed. How can you discount the math and tell me that the spring rate doesn't make a difference?

Granted this is an extreme example, but it is plausible. These are readily available springs made for the TJ. You might like to argue that this Jeep is not setup properly with these springs. I agree. But you don't get to make that argument because you said all the spring does is set height. In this case both springs set the Jeep to the exact same height and had the exact same travel. The only difference is the spring rate.

That is how you tune your suspension by using only spring rate. Given everything else is equal. A soft spring will compress further and rebound slower. A firmer spring will compress less and rebound quicker.

I admit I don't have the experience that many of you have. So in practical terms the difference may be minimal or not noticable at all. But I will still argue that based on the math, the difference must still be there.

Have a Happy 4th of July.

If you folks would set up and tune just one set of coil overs well for a TJ, all of this bullshit would go away. There are literally millions of words typed up to support the erroneous position that it possible to tune ride quality with springs. It isn't.

 

[mrblaine]

So I guess if I take the rear seat out my Jeep still weighs the same? And then I put 6 bags of concrete back there, Still weighs the same?

Let's look at the spring a bit differently. Using airbags instead of bent steel. Still act as the springs. So if I put 75 psi in the airbags it will ride the same as when I have 250 psi in the bags? Only thing changing is the effective spring rate. So in your opinion the Jeep will ride the same at 75 and 250 psi? Same Jeep. Same shock. Same tire.
The fact is that all of them work in combination to provide ride quality. Change any of them and you change how it rides. Change the vehicle weight (yes, it does change) and you change how it rides. Change the spring rate and you change how it rides.

You can not change the spring rate to a 300% stiffer rate and have the same ride height. If you put 250 psi in any air bag that can take that much, it will be at the full limit of extension and every tiny bump will be trying to yank the axles off of the ground which will deliver a phenomenally jarring ride.

 

[Goatman]

So, a guy wrapped in bubble wrap jumping off a building is a realistic illustration? But putting bags of concrete isn't?
Changing ride height an inch does not change the way a shock functions.
No one (at least not me) is claiming that suspension is or can be tuned to perfection by merely changing the spring rate. But it IS part of the suspension. And changing it DOES affect ride.
Why else would every manufacturer spend so much time and money to develop each and every vehicle they build? Just slap any old spring under there and perfect ride.
And yet everyone says to lower tire pressure a few psi and perfect ride.
Or change the shocks to a softer valving perfect ride.

Ever go mattress shopping? How many different choices are out there. To soft for you? Try this one. It has firmer springs. Too hard? How about this? Its springs are softer.
(Showing my age here) watch a kid on a pogo stick. Then watch a kid twice as heavy, or half as light. It's just a fucking spring with a handle and foot pegs. Yet every one of those kids bounce differently because of the relative spring rate to their weight.

Shocks do one thing. And only one thing. They control the movement of the spring. That is it. They perform no other function. If the spring is too stiff to deflect (bounce) it doesn't matter what kind of shock you have. The suspension doesn't move. Have a spring too soft it coil binds and it doesn't matter about the shock at all.

I am done trying to explain why the square peg doesn't fit in the round hole.

 

[mrblaine]

I am done trying to explain why the square peg doesn't fit in the round hole.

That is actually a good thing because there is a glaring flaw in each of your examples that you are overlooking that proves you incorrect in all of your assumptions.

 

[jjvw]

So, a guy wrapped in bubble wrap jumping off a building is a realistic illustration? But putting bags of concrete isn't?
Changing ride height an inch does not change the way a shock functions.
No one (at least not me) is claiming that suspension is or can be tuned to perfection by merely changing the spring rate. But it IS part of the suspension. And changing it DOES affect ride.
Why else would every manufacturer spend so much time and money to develop each and every vehicle they build? Just slap any old spring under there and perfect ride.
And yet everyone says to lower tire pressure a few psi and perfect ride.
Or change the shocks to a softer valving perfect ride.

Ever go mattress shopping? How many different choices are out there. To soft for you? Try this one. It has firmer springs. Too hard? How about this? Its springs are softer.
(Showing my age here) watch a kid on a pogo stick. Then watch a kid twice as heavy, or half as light. It's just a fucking spring with a handle and foot pegs. Yet every one of those kids bounce differently because of the relative spring rate to their weight.

Shocks do one thing. And only one thing. They control the movement of the spring. That is it. They perform no other function. If the spring is too stiff to deflect (bounce) it doesn't matter what kind of shock you have. The suspension doesn't move. Have a spring too soft it coil binds and it doesn't matter about the shock at all.

I am done trying to explain why the square peg doesn't fit in the round hole.

Just to pick one, your pogo stick example comparing a fat kid and a skinny kid involves a change in ride height. You gotta quit doing that if you want to do this.

 

[mrblaine]

Just to pick one, your pogo stick example comparing a fat kid and a skinny kid involves a change in ride height. You gotta quit doing that if you want to do this.

Don't ignore the obvious. The pogo stick has no damping and if it did, I could alter the damping in each scenario so the fat kid and the skinny kid would both hit the bottom of the spring at the same time. It wouldn't be comfortable for the fat kid with compromised ride height since the time to do work is less, but it could be done.

 

[jjvw]

Don't ignore the obvious. The pogo stick has no damping and if it did, I could alter the damping in each scenario so the fat kid and the skinny kid would both hit the bottom of the spring at the same time. It wouldn't be comfortable for the fat kid with compromised ride height since the time to do work is less, but it could be done.

@Goatman, this is how you use a pogo stick as an example.

 

[Goatman]

Pogo stick was to show that spring rate makes a difference. His claim that with the right shock he could affect the movement of the spring is my point. A shock is used to control the spring. That is what it does. It controls the spring. But if the spring is stiff enough to not move then a shock will do nothing. Nothing. And how a guy in bubble wrap jumping off a building is relevant, but a pogo stick isn't just shows ignorance of how a spring works. P.S. they don't wrap themselves in bubble wrap, they vary the amount of air pressure in the crash bag at the bottom (sorta just like changing the spring rate)

It takes the entire suspension to control vehicle ride quality. If it didn't they wouldn't waste time and money in developing each piece.
And if a change of an inch of 'ride height' made such a big difference then every time you hit a bump the shock would need to be changed out for one that is made for an inch high bump because the spring just compressed an inch. Fuck no. A shock is made to work for its entire range. You don't need a different shock if you have 2 extra people in the vehicle. It settles the ride height down a bit and the shock still works fine. Just fine. Take your hard top and back seat out and the vehicle changes ride height. No new shock is required. That is just plain stupid. Plain stupid. So either you need to switch out shocks every time you go home from the grocery store or that change in ride height dosen't make the shock stop working. Next I'll help explain why boats float, or how gravity works if you need help there too.

 

[jjvw]

Give us a clear and concise method that we can all use to tune the ride through springs.

 

[Goatman]

Once again, it takes the entire system to be right for you to get the best ride quality. There IS no 'one size fits all' way to 'tune the ride'.
Some folks want a softer ride, others like a stiffer ride. Some want a lot of uptravel, others want to have a ton of droop and be sure the spring stays tightly seated.

But here is a start...
The purpose of a suspension is to allow the unsprung weight of a vehicle (the tires and axles) to move up and down easily over road inconsistencies while allowing the vehicle's sprung weight (the part you sit in) to remain stable. That's it in a nutshell. Easy to say, not so easy to achieve.
There are 3 basic parts to a suspension. Tires, springs, shocks. Tire sidewall is an important part of the system. It acts as a spring to help absorb road shock. Too narrow, thick, stiff, hard and instead of absorbing road shock it will transmit it farther up into the suspension. This is why (for a TJ) you want a soft sidewall with lower tire pressure. This allows the sidewall to flex over imperfections in the road. Decrease sidewall (run 18 or 20" rims), increase load range or psi and you stiffen the ride, ALL OTHER THINGS BEING EQUAL.

Springs perform 2 basic things. They establish static ride height and allow the unsprung weight to move while isolating the sprung weight. Ride height is easy. Want it to ride higher? Use a longer (taller) spring of the same rate, OR use a higher rate spring that won't compress as much with the vehicle weight. Sounds easy, but it's not. Higher spring rate means the spring will compress LESS when a vehicle hits a bump ALL OTHER THINGS BEING EQUAL. That means the spring will transmit the shock farther up. Same as a stiffer tire. The difference is, there IS no farther up. Which means that shock is transmitted to the sprung weight of the vehicle (the part you sit in). Use a softer spring and it can compress much easier when the tire moves upward. This means the spring can absorb more of the shock, preventing it from going into the vehicle. BUT THERE IS A CATCH! A softer spring will continue to oscillate easier and for a longer time than a stiffer spring. And this will transfer into the vehicle as repeated bouncing long after the road shock has gone. So you have 2 choices. A spring that doesn't compress much transfering the road shock into the vehicle (high spring rate) or a spring that compresses easily that absorbs the road shock but transfers the continued oscillations into the vehicle. AGAIN, ALL OTHER THINGS BEING EQUAL.

The 3rd part of the suspension is the shock absorber. It does one thing, and one thing only. It restricts the movement of the spring. Yes a nitrogen or gas shock extends by itself, but that is negligible to the suspension and only a byproduct of the gas used to prevent aeration (foaming) and shock fade. So, since the shock only does one thing (again, control the movement of the spring) let's look at how IT affects vehicle ride.
The soft spring encounters a road shock...absorbs the shock by compressing, preventing the shock from transferring into the vehicle (so far this is great!) But then wants to continue to bounce. Well, a shock is made to restrict that bouncing. Restricting the soft spring from continuing. Stoping the bouncing from affecting the vehicle. Between the correct tire design absorbing some of the road shock, transferring the rest upward, and that compliant spring absorbing the remainder of the road shock, and the shock absorber having the propper valving to control the excess movement of the softer spring, the unsprung weight is able to smoothly move over the surface with minimal transfer of shock into the sprung weight of the vehicle. Just beautiful because ALL parts of the suspension are working together properly to allow the vehicle to move smoothly over the surface. BUT... (there's always a but in there, isn't there.)...
BUT...what if you stuck a spring in there with too high of a spring rate? LET'S SEE...
Tire hits a bump. Good tire selection means part of that shock is absorbed by the sidewall, the rest is transferred up. Remainder of shock is transferred to the spring, but now the spring is too stiff to compress (enough), so the remainder of that shock is transferred into the vehicle. What about the shock absorber??? Well, it did nothing. Remember the shock absorber can only control the motion of the spring. The hard spring didn't compress, so the shock absorber does little to nothing about the suspension's ability to dampen the road inconsistencies.
ONE OTHER WAY THIS COULD WORK... good tire choice...nice compliant spring of the proper height.... shitty choice in shock absorber. It's calving is too restrictive. It is so stiff that it prevents the compliant spring from it's initial movement. Therefore instead of the spring being able to absorb the road shock, it gets transferred up into the vehicle. No matter how perfect the spring is matched to a vehicle, poor shock absorber choice can still cause a harsh ride quality. But..(another one? Geesh!) But no matter how perfect a shock absorber is, if the spring is too stiff to compress over road imperfections then the shock can do little to improve things.

Hopefully this is helpful in explaining how the different parts of a suspension interact with each other and how a poor choice of one part can negate the other parts from doing their job.

 

[jjvw]

When you set up coilovers, how do you tune the ride through the springs? What does one look for? What changes get made?

 

[Fargo]

Give us a clear and concise method that we can all use to tune the ride through springs.

Didn't I do that back in post #239?

I will summarize that post saying; Given everything else is equal. A soft spring will compress further at a faster rate. A firm spring will compress less at a slower rate. The softer spring will also be easier to control with a shock absorber because, as you have stated, the shock has more travel distance to control the spring.

Is their anything in the statement above you disagree with?

Of course, you will still need to use shock absorbers to control the spring. But that will always be the case. You also can not show me how to control the ride with shock absorbers alone. You still need springs. They work together. But just as you can change the ride quality by switcing shock absorbers I can also change ride quality by switching springs. Even if they are at the same ride height, the compression and rebound rates of different springs will affect ride quality.

Also, to keep things fair, you can not limit my spring choice to what's available over the counter, then allow yourself the freedom to utilize a custom tuned shock. If you get to use a custom tuned shock in your argument, I also get to use a custom tuned spring. I can order custom spring rates and lengths from a number of manufacturers online at a cost similar to over the counter. So I can infact get a softer spring that will sit at the same ride height as a firm spring. With any rate or combinations of rates I like. Just like your custom shock tune.

My point is this is a suspension system. All things work together. I can change ride quality by chaning springs and you can change ride quality through changing shocks.

Please hear me that I am not saying that changing springs is the best way to change the ride quality. Springs should be chosen based on the weight they need to support and the amount of travel you have available to support it. Tuning the shocks is the proper way to adjust ride quality. But changing springs will affect that ride non the less.

 

[jjvw]

Didn't I do that back in post #239?

I will summarize that post saying; Given everything else is equal. A soft spring will compress further at a faster rate. A firm spring will compress less at a slower rate. The softer spring will also be easier to control with a shock absorber because, as you have stated, the shock has more travel distance to control the spring.

Is their anything in the statement above you disagree with?

Of course, you will still need to use shock absorbers to control the spring. But that will always be the case. You also can not show me how to control the ride with shock absorbers alone. You still need springs. They work together. But just as you can change the ride quality by switcing shock absorbers I can also change ride quality by switching springs. Even if they are at the same ride height, the compression and rebound rates of different springs will affect ride quality.

Also, to keep things fair, you can not limit my spring choice to what's available over the counter, then allow yourself the freedom to utilize a custom tuned shock. If you get to use a custom tuned shock in your argument, I also get to use a custom tuned spring. I can order custom spring rates and lengths from a number of manufacturers online at a cost similar to over the counter. So I can infact get a softer spring that will sit at the same ride height as a firm spring. With any rate or combinations of rates I like. Just like your custom shock tune.

My point is this is a suspension system. All things work together. I can change ride quality by chaning springs and you can change ride quality through changing shocks.

Please hear me that I am not saying that changing springs is the best way to change the ride quality. Springs should be chosen based on the weight they need to support and the amount of travel you have available to support it. Tuning the shocks is the proper way to adjust ride quality. But changing springs will affect that ride non the less.

You can answer the question about coilovers, then.

 

[Fargo]

Once again, it takes the entire system to be right for you to get the best ride quality. There IS no 'one size fits all' way to 'tune the ride'.
Some folks want a softer ride, others like a stiffer ride. Some want a lot of uptravel, others want to have a ton of droop and be sure the spring stays tightly seated.

But here is a start...
The purpose of a suspension is to allow the unsprung weight of a vehicle (the tires and axles) to move up and down easily over road inconsistencies while allowing the vehicle's sprung weight (the part you sit in) to remain stable. That's it in a nutshell. Easy to say, not so easy to achieve.
There are 3 basic parts to a suspension. Tires, springs, shocks. Tire sidewall is an important part of the system. It acts as a spring to help absorb road shock. Too narrow, thick, stiff, hard and instead of absorbing road shock it will transmit it farther up into the suspension. This is why (for a TJ) you want a soft sidewall with lower tire pressure. This allows the sidewall to flex over imperfections in the road. Decrease sidewall (run 18 or 20" rims), increase load range or psi and you stiffen the ride, ALL OTHER THINGS BEING EQUAL.

Springs perform 2 basic things. They establish static ride height and allow the unsprung weight to move while isolating the sprung weight. Ride height is easy. Want it to ride higher? Use a longer (taller) spring of the same rate, OR use a higher rate spring that won't compress as much with the vehicle weight. Sounds easy, but it's not. Higher spring rate means the spring will compress LESS when a vehicle hits a bump ALL OTHER THINGS BEING EQUAL. That means the spring will transmit the shock farther up. Same as a stiffer tire. The difference is, there IS no farther up. Which means that shock is transmitted to the sprung weight of the vehicle (the part you sit in). Use a softer spring and it can compress much easier when the tire moves upward. This means the spring can absorb more of the shock, preventing it from going into the vehicle. BUT THERE IS A CATCH! A softer spring will continue to oscillate easier and for a longer time than a stiffer spring. And this will transfer into the vehicle as repeated bouncing long after the road shock has gone. So you have 2 choices. A spring that doesn't compress much transfering the road shock into the vehicle (high spring rate) or a spring that compresses easily that absorbs the road shock but transfers the continued oscillations into the vehicle. AGAIN, ALL OTHER THINGS BEING EQUAL.

The 3rd part of the suspension is the shock absorber. It does one thing, and one thing only. It restricts the movement of the spring. Yes a nitrogen or gas shock extends by itself, but that is negligible to the suspension and only a byproduct of the gas used to prevent aeration (foaming) and shock fade. So, since the shock only does one thing (again, control the movement of the spring) let's look at how IT affects vehicle ride.
The soft spring encounters a road shock...absorbs the shock by compressing, preventing the shock from transferring into the vehicle (so far this is great!) But then wants to continue to bounce. Well, a shock is made to restrict that bouncing. Restricting the soft spring from continuing. Stoping the bouncing from affecting the vehicle. Between the correct tire design absorbing some of the road shock, transferring the rest upward, and that compliant spring absorbing the remainder of the road shock, and the shock absorber having the propper valving to control the excess movement of the softer spring, the unsprung weight is able to smoothly move over the surface with minimal transfer of shock into the sprung weight of the vehicle. Just beautiful because ALL parts of the suspension are working together properly to allow the vehicle to move smoothly over the surface. BUT... (there's always a but in there, isn't there.)...
BUT...what if you stuck a spring in there with too high of a spring rate? LET'S SEE...
Tire hits a bump. Good tire selection means part of that shock is absorbed by the sidewall, the rest is transferred up. Remainder of shock is transferred to the spring, but now the spring is too stiff to compress (enough), so the remainder of that shock is transferred into the vehicle. What about the shock absorber??? Well, it did nothing. Remember the shock absorber can only control the motion of the spring. The hard spring didn't compress, so the shock absorber does little to nothing about the suspension's ability to dampen the road inconsistencies.
ONE OTHER WAY THIS COULD WORK... good tire choice...nice compliant spring of the proper height.... shitty choice in shock absorber. It's calving is too restrictive. It is so stiff that it prevents the compliant spring from it's initial movement. Therefore instead of the spring being able to absorb the road shock, it gets transferred up into the vehicle. No matter how perfect the spring is matched to a vehicle, poor shock absorber choice can still cause a harsh ride quality. But..(another one? Geesh!) But no matter how perfect a shock absorber is, if the spring is too stiff to compress over road imperfections then the shock can do little to improve things.

Hopefully this is helpful in explaining how the different parts of a suspension interact with each other and how a poor choice of one part can negate the other parts from doing their job.

Nice description, I was writing my post when you posted so I didn't see this. Good job explaining the roles of tires, springs and shocks.

 

[Fargo]

You can answer the question about coilovers, then.

I've never touched coil overs before. So correct me if I am wrong. But why would they be any different than standard coils? If you have a heavy Jeep, use stiff coils to handle the weight for the amount of travel available. If you have a light Jeep use a lighter coil. If your weight varies from trip to trip, maybe use a light coil on top and something more firm on bottom to carry the weight after the first coil is in full bind. Do the same thing to help slow down travel before hitting the bumpstop. Its still a matter of matching the proper spring rate to the weight of the vehicle and the amount of travel available.

I think the point of argument comes when you say all the spring does is set the ride height. That is simply not true. There can be extreme differences in weight between Jeeps. The proper spring needs to be chosen not just to hold the static ride height of the vehicle, but to handle the dynamic load of a vehicle over undulating road surfaces. One size does not fit all when it comes to springs. The proper spring rate will play a pivotal role in how the weight of the Jeep is handled.

 

[Daz7]

When you set up coilovers, how do you tune the ride through the springs? What does one look for? What changes get made?

 

[jjvw]

View attachment 175260

You've shown us two types of traditional coil springs and two configurations of coilover springs.

Keep going.

 

[Daz7]

You've shown us two types of traditional coil springs and two configurations of coilover springs.

Keep going.

Actually, they are all coil over springs. As you can see in black and white, C and D are tunable. You know more than Eibach?