Shock, Springs & Suspension Information Chart Matrix

AnnDee4444

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I've had a few people ask for access to my shock & spring charts, so I decided to put all this in a sharable format that anyone can access or download & modify. There's more than one tab at the bottom, feel free to view or download.

Shock Matrix
The following fields highlighted in yellow are adjustable.
  • The 'Ride Height' field uses my JLR as a base, but your Jeep may ride differently. Be sure to check the shock eye-to-eye measurements for accuracy.
  • 'Bump Travel' (or Up Travel) just turns some of the text red that is outside of the recommended range
Capture.PNG



OEM Springs: a never complete list of all the spring combinations

2.PNG


Rear Motion Ratio: shows how the rear shock's response isn't linear to suspension travel, and most important at lower ride heights

Spring Rates: a small list of spring rates I have collected from this forum

Caster: another small list, this time of caster measurements using fixed arms

Wheelbase: comparing the JL to other Jeeps

Breakover: how the JL & JT breakover angles change at various heights





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DavidArmen

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Amazing work.
How do I contribute to the OEM shocks spreadsheet? I don’t see a JLUR with 3.6 and auto trans and all sections being True.
 

blnewt

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Like everything you post @AnnDee4444 very helpful thread, thanks!
 
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AnnDee4444

AnnDee4444

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Small update comparing the OEM scrub radius variations, and what effect tire size has.

This is by no means a recommendation of what works or drives well, but it could help in certain scenarios. For example: a 37" tire on OEM JL wheels should use an 11mm-19mm spacer if they want to get back to OEM scrub radius levels.

Scrub Radius Matching OEM.png
 
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AnnDee4444

AnnDee4444

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Found some interesting information about the OEM shocks here
  • JL Sport: Gas charged twin tube shock absorbers with full displacement Multi-Tuned Valve (MTV) technology
  • JL Sahara: High pressure gas charged monotube shock absorbers with MTV technology
  • JL Rubicon: High pressure gas charged monotube shock absorbers with MTV technology and hydraulic rebound stop
 
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AnnDee4444

AnnDee4444

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Here's another slightly interesting thing: When the rear bump stops get longer, the shocks need a longer stroke length to achieve the same flex. To achieve the same flex, a Jeep with +3" rear bump stop would need to have a shock with ~0.5" more stroke than a Jeep with OEM bump stops.

This is assuming the shock's full range is being used during full flex.

Effects of bump stop length on suspension travel.png

Effects of bump stop length on maximum axle angle.png
 

blnewt

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Nice findings Andy, thanks!
 

JeepDeesel

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I've had a few people ask for access to my shock & spring charts, so I decided to put all this in a sharable format that anyone can access or download & modify. There's more than one tab at the bottom, feel free to view or download.

Shock Matrix
The following fields highlighted in yellow are adjustable.
  • The 'Ride Height' field uses my JLR as a base, but your Jeep may ride differently. Be sure to check the shock eye-to-eye measurements for accuracy.
  • 'Bump Travel' (or Up Travel) just turns some of the text red that is outside of the recommended range
Capture.PNG



OEM Springs: a never complete list of all the spring combinations

2.PNG


Rear Motion Ratio: shows how the rear shock's response isn't linear to suspension travel, and most important at lower ride heights

Spring Rates: a small list of spring rates I have collected from this forum

Caster: another small list, this time of caster measurements using fixed arms

Wheelbase: comparing the JL to other Jeeps

Breakover: how the JL & JT breakover angles change at various heights
 

Trill

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@AnnDee4444 I have some information buried away that might be useful.

https://www.jlwranglerforums.com/forum/threads/the-2dr-sport-only-thread.15647/page-20#post-1040143

Some of it is 2dr sport specific hence why I posted in that thread. Other stuff is the same across all models.

In a nutshell,
Front:
At full bump, there is 16.25" between upper and lower shock mounts.
At full extension, the spring begins to lose pre-load at 26.25" between upper and lower shock mounts.

Rear:
At full bump, there is 17" between upper and lower shock mounts.
At full extension, the spring begins to lose pre-load at 27.75" between upper and lower shock mounts.

In that thread I also posted some pictures of how little clearance there is at full bump between the frame and front steering, and between the tub and the axle-side track bar bracket in the rear. This applies across all models and means you need to be very careful changing any of this unless you add significant (2"+) bumpstop, which you will not need if you plan on running 35" tires with Rubicon fenders and properly backspaced wheels.

I am also confused about your post (#7) where you talk about the relation between bump stop and stroke in the rear. I don't think you're saying that if you increase bump stop spacing by 3" that you will then need to increase shock length to compensate. That is obvious and intuitive, and applies to the front as well. But in the rear, due to the angle of the shock, you actually have to increase the length less to compensate for bump stop, than you would in the front.

You can make a rough calculation of this by taking the cosine of the angle that the shock is mounted. In the rear of the JL that's about 30 degrees, giving us a 0.87 conversion factor. So to "make up" for the lost travel from 3" bump stop extensions, you would only need a shock that is (3" x 0.87) longer, or 2.61". In the front, with a nearly vertical shock, a 3" bump stop would require a shock with a 3" longer extended length to compensate.
 
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AnnDee4444

AnnDee4444

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In a nutshell,
Front:
At full bump, there is 16.25" between upper and lower shock mounts.
At full extension, the spring begins to lose pre-load at 26.25" between upper and lower shock mounts.

Rear:
At full bump, there is 17" between upper and lower shock mounts.
At full extension, the spring begins to lose pre-load at 27.75" between upper and lower shock mounts.
Awesome info about the full bump distances. I've been looking for this for some time. I've updated my spreadsheet to indicate when outside of these ranges, and have other plans for how I can use these numbers.

I am also confused about your post (#7) where you talk about the relation between bump stop and stroke in the rear. I don't think you're saying that if you increase bump stop spacing by 3" that you will then need to increase shock length to compensate. That is obvious and intuitive, and applies to the front as well. But in the rear, due to the angle of the shock, you actually have to increase the length less to compensate for bump stop, than you would in the front.

You can make a rough calculation of this by taking the cosine of the angle that the shock is mounted. In the rear of the JL that's about 30 degrees, giving us a 0.87 conversion factor. So to "make up" for the lost travel from 3" bump stop extensions, you would only need a shock that is (3" x 0.87) longer, or 2.61". In the front, with a nearly vertical shock, a 3" bump stop would require a shock with a 3" longer extended length to compensate.
To sum up my thoughts in that post: Shock travel is more effective at lower ride heights. The closer the shock gets to vertical, the more travel is required for the same articulation. In other words: As the shock approaches horizontal, 1" of shock travel offers a lot more axle movement than if the shock was completely vertical.

Here's how I have been figuring it, with the Pythagorean theorem (A² +B² =C²). The shock's mounting angle changes depending on suspension height, but the top of the shock vs. the axle's vertical distance is fairly consistent at 11" (not accounting for the arc of the axle travel... too much math for me).

A = Suspension Height (actually vertical distance to top of shock)
B = 11"
C = Shock Length

Mopar_1941_Body_Decal_JL_82215733.jpg
 

Trill

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Ok I see what you're saying. Do you think the angle changes that much to to appreciably mess with the conversion factor?

With stock bumpstops and 10" of fully utilized stroke:

Compressed:
C = 17" (using my measurement)
B = 11" (your number)
A = 13" (solving for A)

Extended:
C = 27" (adding 10" stroke to C)
B = 11" (your number)
A = 25" (solving for A)

So with stock bumpstops, you get 12" of wheel travel (Aext - Acomp) for a 10" shock stroke using this approach.

Now let's start with 3" bumpstops and 10" of fully utilized stroke:

Compressed:
A = 16" (adding bump stops to this variable is appropriate I believe)
B = 11" (your number)
C = 19.5" (solving for C)

Extended:
C = 29.5" (adding 10" stroke to C)
B = 11" (your number)
A = 27" (solving for A)

So with 3" extended bumpstops, we get 11" of wheel travel (Aext - Acomp) for a 10" shock stroke using this approach.

Now, using the trigonometric hack (stroke / cos(30*)) we split the difference and get 11.5" of wheel travel out of a 10" stroke shock regardless of bump stops since that is not factored.

Your method for solving this proves what you were saying, that you get less value out of shock stroke the more bump stop you run.

My method is always gives the same result.

We both leave a lot of important variables out of the equation.

Interesting experiment, thanks.
 
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AnnDee4444

AnnDee4444

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Ok I see what you're saying. Do you think the angle changes that much to to appreciably mess with the conversion factor?
Not enough to matter honestly. The differences are pretty negligible, but I still went through the motions of calculating just to make sure it wasn't a major factor. It's probably more important for shock valving than anything else.

I realized that I haven't posted this chart here yet... This is what started my thinking about the rear suspension's movements. The orange/red line is applicable to all shocks, with the red portion just being the OEM Rubicon shocks. At 17" shock length, the ratio is 1.31:1, but the difference between an extended Rubicon shock and one 4" longer is only 1.10:1 vs 1.07:1... which is absolutely negligible.
JL Rear Shock Motion Ratio.png
 

Trill

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Good work. If you're up to it, you could also use geometry to give people who buy adjustable track bars with their lift kits a starting point for what length they should be shooting for.

track.png


A is track bar length eye to eye. B and C are imaginary lines. As C (lift) increases, B (lateral axle placement underneath the jeep) will shrink, causing the axle to be pulled to the side. (A) would need to be extended to some variable depending on C to keep B the same as stock. Could also factor for the common raised track bar bracket heights.
 

blnewt

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Andy, not sure if I'm doing something wrong, but on the Shock Matrix section it won't scroll and only goes down to halfway into the Bilstein 1.5-3" shock. Was interested in some Teraflex data if you happen to have that on the list :)
 

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