Spring lift basics

[flanders]

Long time lurker, first time poster.

I am a proud new owner of a Sting grey 2021 JLUR. I have an emotional bound with that piece of metal I'll never be able to explain to my wife.

Although we go to Moab every summer, it will mainly be used as our overlanding rig. Awesome feeling packing everything you need to survive between the axles.

I'm sorry if this has been answered previously, but I've searching like crazy trying to figure this out.
I might be an unworthy jeep owner because I enjoy stock things. I'm an electrical engineer, and I get satisfaction knowing I'm using something within the constraints it was designed/optimised for. I like the power and gas mileage I get with my 33s, and I like having all the angles of my suspension close to stock.

After installing a winch and bull bar, I noticed the front was drooping, so I started looking at spring spacers. I decided if I was going to go through all that work, I might as well go for the 1.5"/2" TF spacers. (Just 4 hockey pucks and nothing else). Here's how I justified it to myself I wasn't changing stock angles.

I believe 'travel' is the distance between the bump stops and full shock extension. With spacers, you don't change the bump stops or the shock, so travel is the same. The only thing that changed its area of operation is the spring. The spring can now be compressed 2" more, and extends 2" less. Since an ideal spring is linear, I think that means it takes more force to hit the bump stop, and there is also more force on the shock when fully extended. I don't think that's too big of a deal, but I could be wrong.

Everything else other than the spring still sees the same range of movement, however at rest the suspension is biased higher. Basically I've traded equal amount of 'extension' range for 'compression' range, so the ratio is different. To me, I felt like that was a minimal change and kept things stockish.

Now to muddy the water, I'm pretty confused what shock extenders are for. If I were to throw a stock extender on my shocks, now I've changed the range of movement the shock sees. Now when I hit the bump stop, the shock is compressed 2 extra inches, like the spring. It also means the tire extends 2 extra inches when fully extended, but in the spirit of keeping things as stock as possible, I'm okay not gaining those 2 inches.

In my mind, 4 pucks without shock extensions is more true to stock. Is the only reason people use the extensions is to gain a few inches of travel when fully extended?

Thanks in advance for the help, and sorry for so much rambling.

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[Some Random Guy]

I think you have something backwards. The suspension can compress 2” LESS and could extend 2” MORE IF the shocks didn’t limit it, but they do (thus shock extensions exist to gain that extension). The spring capabilities don’t change, but the weight keeps them more compressed and makes it easier to fully compress them. I read somewhere over-compressing springs regularly is not good for them, but could be full of it.

 

[flanders]

Forgive me as I try to understand.

If I didn't change the bump stop, what is causing the 2" of less compression?

 

[Some Random Guy]

Forgive me as I try to understand.

If I didn't change the bump stop, what is causing the 2" of less compression?

The spring will hit full compression 2” earlier with a 2” spacer. I was referring to the suspension travel as a whole, not just the spring.

 

[Terminex]

Full extension is determined by the shock extended length. (Assuming you are still within the limits of the extension of the control arms & track bar)

lets say full up travel from ride height is 5” stock. (I am making this number up to make an easy explanation)

if you put a 2” spacer on without shock extensions, you now only have 3” of up travel from ride height.

if you truly want to stay closer to stock with 2” spacers, you also need 2” shock extensions, as well as 2” bump stop extensions.

(this is all ignoring the change a 2” lift is making to the geometry of the suspension)

 

[Mx5red]

Full extension is determined by the shock extended length. (Assuming you are still within the limits of the extension of the control arms & track bar)

lets say full up travel from ride height is 5” stock. (I am making this number up to make an easy explanation)

if you put a 2” spacer on without shock extensions, you now only have 3” of up travel from ride height.

if you truly want to stay closer to stock with 2” spacers, you also need 2” shock extensions, as well as 2” bump stop extensions.

(this is all ignoring the change a 2” lift is making to the geometry of the suspension)

Is that right? Seems like if you add the spacer then there would be an extra 2” of up travel without else anything changing…
I believe you meant if you had 5” of droop stock and added 2” spacer without extensions, then you’d only have 3” of down travel, since I believe droop is shock-limited…
I think uptravel is limited by frame-axle contact (not spring bind?) or also tire-fender contact, so I think the uptravel would increase by as much spacer as you add (assuming spring compression isn’t the limit).
So, the only point of adding bump stop pads is to make up for bigger tires that most people are adding with a lift.

at least that’s what I’ve gathered learning stuff here. I could be wrong though.

 

[Roky]

Long time lurker, first time poster.

I am a proud new owner of a Sting grey 2021 JLUR. I have an emotional bound with that piece of metal I'll never be able to explain to my wife.

Although we go to Moab every summer, it will mainly be used as our overlanding rig. Awesome feeling packing everything you need to survive between the axles.

I'm sorry if this has been answered previously, but I've searching like crazy trying to figure this out.
I might be an unworthy jeep owner because I enjoy stock things. I'm an electrical engineer, and I get satisfaction knowing I'm using something within the constraints it was designed/optimised for. I like the power and gas mileage I get with my 33s, and I like having all the angles of my suspension close to stock.

After installing a winch and bull bar, I noticed the front was drooping, so I started looking at spring spacers. I decided if I was going to go through all that work, I might as well go for the 1.5"/2" TF spacers. (Just 4 hockey pucks and nothing else). Here's how I justified it to myself I wasn't changing stock angles.

I believe 'travel' is the distance between the bump stops and full shock extension. With spacers, you don't change the bump stops or the shock, so travel is the same. The only thing that changed its area of operation is the spring. The spring can now be compressed 2" more, and extends 2" less. Since an ideal spring is linear, I think that means it takes more force to hit the bump stop, and there is also more force on the shock when fully extended. I don't think that's too big of a deal, but I could be wrong.

Everything else other than the spring still sees the same range of movement, however at rest the suspension is biased higher. Basically I've traded equal amount of 'extension' range for 'compression' range, so the ratio is different. To me, I felt like that was a minimal change and kept things stockish.

Now to muddy the water, I'm pretty confused what shock extenders are for. If I were to throw a stock extender on my shocks, now I've changed the range of movement the shock sees. Now when I hit the bump stop, the shock is compressed 2 extra inches, like the spring. It also means the tire extends 2 extra inches when fully extended, but in the spirit of keeping things as stock as possible, I'm okay not gaining those 2 inches.

In my mind, 4 pucks without shock extensions is more true to stock. Is the only reason people use the extensions is to gain a few inches of travel when fully extended?

Thanks in advance for the help, and sorry for so much rambling.

The simplest way I can explain it is.... first, the spacer doesn’t change spring rate , just ride height. Ideally you want to be in the middle of the shock stroke at ride height. When you add the 2” spacer now the shock is extended 2 “ at ride height. This means it will bottom out on extension quicker over potholes, whoops, etc. unless you add the 2” of bump stop, but then you’ll be hitting the bump stop more often, which will result in a rougher ride on the trail. So the best thing to do is, if you raise ride height 2”, get 2” longer shocks or use shock extensions to keep your shocks in the middle of the stroke or close to it.

 

[Terminex]

Is that right? Seems like if you add the spacer then there would be an extra 2” of up travel without else anything changing…
I believe you meant if you had 5” of droop stock and added 2” spacer without extensions, then you’d only have 3” of down travel, since I believe droop is shock-limited…
I think uptravel is limited by frame-axle contact (not spring bind?) or also tire-fender contact, so I think the uptravel would increase by as much spacer as you add (assuming spring compression isn’t the limit).
So, the only point of adding bump stop pads is to make up for bigger tires that most people are adding with a lift.

at least that’s what I’ve gathered learning stuff here. I could be wrong though.

droop / extension, you have the right idea.

Spring compression could be a concern, in my mind more of a concern with a spacer, than it is with a spring lift. (spacer does not compress) That is one of the reasons for using a bump stop extension. The other reason as you mentioned would be the tires in the fenders.

 

[GATORB8]

Get ready to geek out on this: https://www.jlwranglerforums.com/fo...gs-suspension-information-chart-matrix.66591/

I've downloaded and added the Rubicon shocks with 2" extension.

Stock height:

2" Spacer/Spring lift:

2" Spacer/Spring lift with 2" Bump Stops:

 

[GATORB8]

Get ready to geek out on this: https://www.jlwranglerforums.com/fo...gs-suspension-information-chart-matrix.66591/

I've downloaded and added the Rubicon shocks with 2" extension.

Stock height:

2" Spacer/Spring lift:

2" Spacer/Spring lift with 2" Bump Stops:

One note, you'll need the bumps if you do the extensions, as you can see in the second chart, you are shock limited with extensions on compression without extended bumps.

 

[flanders]

Just realized I accidentally posted this three times... Yes it is my first day on the internet.

English is hard, so here's a picture. I hope it helps more than confuses.

Basically, I want to find the best column.
2nd column was my choice.

PROs:

• Axle doesn't see any positions/angles it didn't see before. No increased chances of inverted sway bar, no new control arm angles, nothing. Ride height angle is different, but that's true for every column other than stock. This was the biggest Pro for me.

CONs:

• Shock no longer centered. I'm failing to see why this is too big of a deal. Isn't the extra compression range more valuable than the lost extension range?
• Spring is tighter on both the Bump stop and fully extended. I still don't know if this is a problem? When the shock is fully extended, there is more spring force. Bad on the shock? But if the opposite side is fully compressed, does the extra spring force on that side cancel each other out?

Thanks for all your help so far.

 

[flanders]

Get ready to geek out on this: https://www.jlwranglerforums.com/fo...gs-suspension-information-chart-matrix.66591/

I've downloaded and added the Rubicon shocks with 2" extension.

Stock height:

2" Spacer/Spring lift:

2" Spacer/Spring lift with 2" Bump Stops:

BTW, I think I'm just starting to realize how much valuable information you just gave me there... These are exactly the numbers I was wondering about. Thanks GATORB8!

 

[GATORB8]

BTW, I think I'm just starting to realize how much valuable information you just gave me there... These are exactly the numbers I was wondering about. Thanks GATORB8!

No problem. @AnnDee4444 is the one to really think for creating the spreadsheet, all I did was add a line for the extensions.

One thought, if you do decide to do shock extensions/bump stops down the road, the only part of the install you'll have to do extra work on is the front bump stops. The shock extensions and rear bump stops can be done easily with wheels on and no extra work.

Just a consideration, but there will be a difference in clearance during articulation. The center of axle rotation will be 2" higher at full stuff, so the frame and undercarriage will be 2" vertically closer to the ground. Trade off is you're COG will be 2" lower, of course.

 

[GATORB8]

Another option, because you don't need to increase bump, you could find a replacement shock that has a compressed length that works with the factory stop, but gets you more extension. The only real net effect would be increased articulation and added room for droop to keep your shocks from "topping" out.

I just ordered Bilstein 5100s, so I've been looking closely at those, I'll include Fox since it's the go to. Both are IFP monotubes around 2" diameter. Both are available in multiple lengths.

Here's the chart with 2" lift, no bump stop extension.

Both the Bilstein 0-1.5 and Fox 0-1.5 have compressed lengths that work with the factory bumps, but both allow for additional droop due to the stroke being longer. Net gain in front axle articulation angle would be 18% and 33% respectively. The Fox 1.5 with no bump will actually give you more articulation than the Fox 2-3 with the min .5" bump extension you would need.

 

[Jank4AU]

Just a consideration, but there will be a difference in clearance during articulation. The center of axle rotation will be 2" higher at full stuff, so the frame and undercarriage will be 2" vertically closer to the ground. Trade off is you're COG will be 2" lower, of course.

This is confusing to me. If you're only lifting the body, or anything for that matter, how could the COG possibly be lower. You're moving weight higher which would necessitate the COG moving upwards as well. Also, axle rotation...how would that be 2" higher at full stiff? None of these methods of lifting increase the height of the axle from the ground, only the body off of the axle. The only way to do that is with larger tires. When you talk about axle rotation, it may go up if the driver side tire stays at the same surface height and the passenger side travels up over a log/bump/rock/hill. But even then, the full travel would be less than the entire lift as the center wouldn't move as much as the extreme ends. Please help me out here...

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