Usable Articulation

[StG58]

Let's discuss usable articulation. What is it? How do you achieve it? I'm assuming that it varies from the Mall to Johnson Valley...but how do you decide how much is enough, and then build for that target?

I'll be off line for a few hours, so mull it over and post up your thoughts. Thanks!

 

[jjvw]

Good topic!

What determines the usable articulation?

2003 Rubicon

 

[bobthetj03]

There was similar conversation on another forum. I'll review my notes and give an opinion. Here's a secondary question. Do bump stop extensions limit your usable articulation?

 

[jjvw]

.... Do bump stop extensions limit your usable articulation?

Are the bumps set to be only as long as they need to be to prevent interference between components?

2003 Rubicon

 

[bobthetj03]

Are the bumps set to be only as long as they need to be to prevent interference between components?

2003 Rubicon

Yes.

 

[Rob5589]

Usable is relative. I have as much as the shocks will allow, which is the limiting factor on my set up. @jjvw has a bunch more than stock due to the significant mods he made to the mounts and such. Either way, you do not want to limit/waste travel with excessive bump stops.

 

[jjvw]

Usable is relative. I have as much as the shocks will allow, which is the limiting factor on my set up. @jjvw has a bunch more than stock due to the significant mods he made to the mounts and such. Either way, you do not want to limit/waste travel with excessive bump stops.

For simplicity's sake, I would define the useable range of suspension travel to be between the bump stops and the free length of the spring.

If you can find ways to safely push the boundaries on either end without creating unsolvable problems then you'll get more travel.

Knowing what those problems can be is helpful in understanding where the usable articulation is.

2003 Rubicon

 

[StG58]

Interesting...

I was out playing awhile ago and found a nice boulder half buried in the dirt. After staring at it for a few minutes , I decided to "twist" up the suspension on my basically stock at the time SE. 31" tires were the only mods.

Ran the drivers side front tire up the boulder until the Jeep stopped due to a loss of traction. Two tires on opposite corners at full droop and off the ground, two at full stuff. I had to use momentum to get there because no lockers. That got me to thinking... Even with both rear tires on the ground, there was a point where the drooped tire lost traction. With lockers, it wouldn't have been noticeable. So the usable articulation was less than the total available articulation in that instance. By a couple of inches.

 

[jjvw]

... That got me to thinking... Even with both rear tires on the ground, there was a point where the drooped tire lost traction. With lockers, it wouldn't have been noticeable. So the usable articulation was less than the total available articulation in that instance. By a couple of inches.

What was limiting the droop? What was limiting the up? How could you get more of one or the other or both? What would more of either have accomplished?

Everyone play along. I'm hoping to go on a journey here...

2003 Rubicon

 

[StG58]

What was limiting the droop? What was limiting your up? How could you get more of one or the other or both? What would more of either have accomplished?

2003 Rubicon

In the front, it was the sway bar for droop. It wasn't disconnected. On the stuffed side in the front, it was the bump stop cup. The bump stop was fully compressed into the cup. Now, with further changes to the front and rear suspension, it'll still be the front bump stop cup for stuff and the shock for droop. Didn't examine the rear closely, so I'll have to assume a similar situation.

 

[jjvw]

In the front, it was the sway bar for droop. It wasn't disconnected. On the stuffed side in the front, it was the bump stop cup. The bump stop was fully compressed into the cup. Now, with further changes to the front and rear suspension, it'll still be the front bump stop cup for stuff and the shock for droop. Didn't examine the rear closely, so I'll have to assume a similar situation.

Good catch on the bump stop cup. Short of major modifications, that is effectively your upper limit to travel.

If you had more droop and a sway bar that allowed more movement (or disconnected), what would have happened on that rock where you lifted tires of the ground?

2003 Rubicon

 

[StG58]

I would have lifted the rear tire still, I think, but the front tires would have been in contact with the ground, and pulling longer. Until the drooped front tire unloaded enough to loose traction anyway. At some point I would have been wishing for rock rails, because the body would have dropped onto the rock. But that's a different discussion.

 

[jjvw]

In short, you would have climbed further up that rock because the Jeep would have maintained tire traction to the ground longer, correct?

2003 Rubicon

 

[jjvw]

Let's ignore adding bump stop to fit longer shocks or bigger tires, for now.


What kinds of things can happen to a drooping axle when you add a really long shock with lots of droop?

2003 Rubicon

 

[StG58]

In short, you would have climbed further up that rock because the Jeep would have maintained tire traction to the ground longer, correct?

2003 Rubicon

Until the offside front tire unloaded, yes. The rear would have lifted at the same point, because the fully stuffed front twisted the Jeep enough to lever it off the ground.

 

[StG58]

Let's ignore adding bump stop to fit longer shocks or bigger tires, for now.


What kinds of things can happen to a drooping axle when you add a really long shock with lots of droop?

2003 Rubicon

At some point, the springs stop putting force on the tire, unloading it and stopping traction. (Ignoring the springs coming unseated and various bits bumping into things they ought not bump into)

 

[bobthetj03]

How tippy did you feel in that scenario Stig? Would more up travel or more droop have improved your results?

 

[jjvw]

At some point, the springs stop putting force on the tire, unloading it and stopping traction. (Ignoring the springs coming unseated and various bits bumping into things they ought not bump into)

Correct. Only the weight of the axle and tire is providing tractive force against the ground, essentially some but not much. That is effectively the bottom end of the useful travel.

Now...

Two coils provide the same ride height, but one is a softer spring rate than the other. What happens at droop?

2003 Rubicon

 

[StG58]

How tippy did you feel in that scenario Stig? Would more up travel or more droop have improved your results?

Not tippy at all. Didn't have any issues opening the door and hopping out, other than it was a loooong ways down. In hindsight, that's a bit strange. The rig should have rocked some with my fat backsides flailing about. Didn't seem to though.

 

[StG58]

Correct. Only the weight of the axle and tire is providing tractive force against the ground, essentially some but not much. That is effectively the bottom end of the useful travel.

Now...

Two coils provide the same ride height, but one is a softer spring rate than the other. What happens at droop?

2003 Rubicon

The softer spring must compress more to support the same weight, so it has to get longer to fully unload...so it must exert down pressure at more droop.