New lift, funky symptoms. Need advice. UPDATE

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JT1

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The JK version is 1.5” clamp, that’s what I’m using because my synergy tie rod is 1.5”. The JL tie rod is 1-5/8” so if you plan on upgrading your tie rod make sure it’s the right diameter to fit the stabilizer you get.
Just measured my tie rod, looks like 1.530 on my calipers.. I'm guessing the 1.5" clamp should work.
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JT1

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Could you have accidentally achieved zero scrub radius?

“Most vehicles will not be designed with zero scrub radius, but changes in ride height and wheel offset can unintentionally create a zero scrub radius. When scrub radius is zero, tension on the steering system is reduced and vehicle handling will tend to be unstable. Zero scrub radius also causes the tires to scrub in the opposite direction of rotation during turns (tire squirm). This has a negative effect on handling in turns and affects overall tire wear.”

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I don't think so. I read that thread, and a couple others. Was there ever a definitive answer on the steer axis inclination? Great point though.. may need to get some colored chalk and give it a try..
 

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Could you have accidentally achieved zero scrub radius?

“Most vehicles will not be designed with zero scrub radius, but changes in ride height and wheel offset can unintentionally create a zero scrub radius. When scrub radius is zero, tension on the steering system is reduced and vehicle handling will tend to be unstable. Zero scrub radius also causes the tires to scrub in the opposite direction of rotation during turns (tire squirm). This has a negative effect on handling in turns and affects overall tire wear.”

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Interesting point.
 
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I don't think so. I read that thread, and a couple others. Was there ever a definitive answer on the steer axis inclination? Great point though.. may need to get some colored chalk and give it a try..
I don't know. I'm assuming since it is RWD when in 2WD mode that it runs Positive. My alignment sheet has me at 12.8 and 13 (both positive) SAI, but I haven't done the trigonometry to see if my scrub radius in positive or negative. If positive, a bigger tire may push back to neutral. I've never put that much effort into it since nobody ever mentioned it here in the JL forum. I'm wondering if you can contact those with your same wheel/tire combo on the JT forum and see if they've noticed a similar phenomenon with the steering flopping about (paraphrase, but thats' the detail that caught my attention).
 
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I don't think so. I read that thread, and a couple others. Was there ever a definitive answer on the steer axis inclination? Great point though.. may need to get some colored chalk and give it a try..
Using the only chart I found, it looks like to maintain factory scrub radius, I need a +25 offset wheel with the 37s. I don't REALLY wanna drop $1000 on some AEVs to get there..
 

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Using the only chart I found, it looks like to maintain factory scrub radius, I need a +25 offset wheel with the 37s. I don't REALLY wanna drop $1000 on some AEVs to get there..
I'm not at all suggesting emulating the factory scrub radius, just get away from 0. Above I suggested contacting other JT owners with the same wheel/tire and asking the question about floppy steering so you can rule out scrub radius, or they'll all say they noticed it and you can guess a new wheel or tire might help at that point.
 
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JT1

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I don't know. I'm assuming since it is RWD when in 2WD mode that it runs Positive. My alignment sheet has me at 12.8 and 13 (both positive) SAI, but I haven't done the trigonometry to see if my scrub radius in positive or negative. If positive, a bigger tire may push back to neutral. I've never put that much effort into it since nobody ever mentioned it here in the JL forum. I'm wondering if you can contact those with your same wheel/tire combo on the JT forum and see if they've noticed a similar phenomenon with the steering flopping about (paraphrase, but thats' the detail that caught my attention).
The steering is strange for sure. What it feels like while driving it, is when the right tires are high (road drains left) is that the body leans over and it self steers down the hill.. It's predictable and controllable at low speed, but gets sketchy on bumpy 2 lanes at 50+
 

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The steering is strange for sure. What it feels like while driving it, is when the right tires are high (road drains left) is that the body leans over and it self steers down the hill.. It's predictable and controllable at low speed, but gets sketchy on bumpy 2 lanes at 50+
Adding a little more caster on the passenger side helps with road crown, I'm at 6.0 driver and 6.3 passenger, but it sounds like you are experiencing more than just road crown pull or at least what I have experienced from road crown.
 
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I'm not at all suggesting emulating the factory scrub radius, just get away from 0. Above I suggested contacting other JT owners with the same wheel/tire and asking the question about floppy steering so you can rule out scrub radius, or they'll all say they noticed it and you can guess a new wheel or tire might help at that point.
If +25 ish on a 37 is maintaining factory (which is about an inch of scrub) And I'm at 0, that should increase scrub to 2", right? Or did I move something the wrong way..
 

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Using the only chart I found, it looks like to maintain factory scrub radius, I need a +25 offset wheel with the 37s. I don't REALLY wanna drop $1000 on some AEVs to get there..
That’s why you don’t hear about it on here or in the Jeep mod community. It’s not that big of effect and it’s usually squashed by after market steering components and the ability to run higher caster with the aid of the FAD. Guys just aren’t going to run their rigs a certain way to get scrub radius perfect and sacrifice the stance and look they’ve always dreamed about.
 

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If +25 ish on a 37 is maintaining factory (which is about an inch of scrub) And I'm at 0, that should increase scrub to 2", right? Or did I move something the wrong way..
I wouldn't even worry about the math unless multiple people with your same setup have noticed the same problem, then you can revisit it. A wider tire would help (I can't remember if the pats are 12.5 or 13.5, so that may not be an option. Playing with caster will allow your camber to take you out of 0 too, so increasing it or decreasing it would get you out of that muddy zone. Pinion angle and driveshaft length start coming into play though, so I'll quickly get out of my depth here.
 
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That’s why you don’t hear about it on here or in the Jeep mod community. It’s not that big of effect and it’s usually squashed by after market steering components and the ability to run higher caster with the aid of the FAD. Guys just aren’t going to run their rigs a certain way to get scrub radius perfect and sacrifice the stance and look they’ve always dreamed about.
Agreed, I don't like tire poke, and less is better in my eye, but full articulation and full steering are definitely more important.

I'm about to glue a gopro under there and see what the heck is going on
 
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I wouldn't even worry about the math unless multiple people with your same setup have noticed the same problem, then you can revisit it. A wider tire would help (I can't remember if the pats are 12.5 or 13.5, so that may not be an option. Playing with caster will allow your camber to take you out of 0 too, so increasing it or decreasing it would get you out of that muddy zone. Pinion angle and driveshaft length start coming into play though, so I'll quickly get out of my depth here.
they are 12.5. I can dial caster up or down.. currently on the flats next to the front cover, I'm essentially perpendicular to the ground. That should give me approx 6*
 

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You can't squash geometry.

The only practical way to retain scrub radius when lifting a Jeep and jamming big tires under it is to run a axle that is wide enough to allow you to place the tires in the right location for the SAI.

It's kinda a big deal if you don't want to learn how to drive a Jeep with mucked up geometry.
 
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