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  #1  
Old September 7th, 2020, 21:40
4x4JeePmaNthINg's Avatar
4x4JeePmaNthINg 4x4JeePmaNthINg is offline
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alignment?s

99 on 3 link, 35s, y link, 3.5" springs

I need to adjust my caster because I have some bumper steer, the trac and drag link angles are very good, its not that. Toe in ive adjusted to FSM.

I was reading some on alignment and someone suggested that the toe in will change with bigger tires and that for this reason a factory/ shop machine (tire mounted) alignment is not advised. Their theory revolves around the increased tire height. If you consider factory tow specs and think of taking your measurements from the tires mimicking an upside down V, the larger tire would offset this spec.

can anyone confirm this and if this hold true, how much toe in do you adjust to?

thanks

The jeep also pulls right, I know factory is set up this way, but I need to calm it down some. Is there a good measurement for the distance the DS/PS front axle should be from the rear axle?
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  #2  
Old September 8th, 2020, 04:26
SlowXj SlowXj is offline
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alignment?s

On my rig (3.5 lift true 3 link and 35s) I do my own alignments. I run 1/8" toe measured at the center of the height of the tire. 6ish degrees of caster measured at the top of the ball joint, and I squared the front axle perfectly measuring to the trans cross member bolts as I assumed those were a perfect placement from the factory. This gives me perfect tire wear and it drives true past 70 mph.

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  #3  
Old September 8th, 2020, 05:49
RCP Phx RCP Phx is offline
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Re: alignment?s

If your toe-in was set in "degrees" and to the factory spec then yes you have to much toe-in. Tire size does change the amount of "toe-in", so just set it using a tape measure and your good to go.
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Old September 8th, 2020, 08:04
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4x4JeePmaNthINg 4x4JeePmaNthINg is offline
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Re: alignment?s

Quote:
Originally Posted by SlowXj View Post
On my rig (3.5 lift true 3 link and 35s) I do my own alignments. I run 1/8" toe measured at the center of the height of the tire. 6ish degrees of caster measured at the top of the ball joint, and I squared the front axle perfectly measuring to the trans cross member bolts as I assumed those were a perfect placement from the factory. This gives me perfect tire wear and it drives true past 70 mph.

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I plan on using a plumb bob front and rear axle to square everything up, the cross member is welded on so the bolts could be used as a reference.

caster ive measured using a magnetic angle finder on the bottom of the C

I will recheck the toe with the tires on, I had used angle iron drilled and bolted to the calipers. worked well but it would need to be bigger for the 35s now.


does anyone know how much of a difference the passenger LCA should have, just to maintain that factory set up?
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Old September 8th, 2020, 08:35
RCP Phx RCP Phx is offline
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Re: alignment?s

BTW, if your having bump-steer then your trackbar/steering link angles "are" off. Nothing else causes bump-steer.
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  #6  
Old September 8th, 2020, 09:30
Evan03 Evan03 is offline
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alignment?s

Why would you care wht factory is set at?

Your castor reading will vary side to side but not much. More due to variances in reading tools

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  #7  
Old September 8th, 2020, 09:31
Evan03 Evan03 is offline
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alignment?s

I agree with Rcp

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  #8  
Old September 8th, 2020, 11:20
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4x4JeePmaNthINg 4x4JeePmaNthINg is offline
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Re: alignment?s

Quote:
Originally Posted by RCP Phx View Post
BTW, if your having bump-steer then your trackbar/steering link angles "are" off. Nothing else causes bump-steer.
I dont know what to tell you then, trac bar and drag link are dead on parallel. Maybe its squirrely from poor caster then, should be easily fixed after adjusting the upper link.

All I know is if I hit a bump she jumps a bit one way or the other.


Evan to be clear Im not trying for factory caster, I know I cant achieve this with a lifted vehicle and maintain a happy drive shaft. From the factory the xj was adjusted so that it does pull passenger ever so slightly, its supposed to take you off the road instead of into oncoming traffic. Its simply a spec that I was trying to maintain while adjusting everything, its a DD so I'm just adjusting it to the the best of my ability.
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  #9  
Old September 8th, 2020, 11:40
Evan03 Evan03 is offline
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alignment?s

I'd imagine it's built into the Cs
Maybe bumpsteer isn't what your experiencing. Or could be track drag length difference

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Old September 8th, 2020, 13:52
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Tim_MN Tim_MN is offline
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Re: alignment?s

Stock, the front/rear wheelbase left/right difference is 10mm longer on the right side to offset crowned pavement.
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  #11  
Old September 8th, 2020, 18:26
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Re: alignment?s

Quote:
Originally Posted by Evan03 View Post
I'd imagine it's built into the Cs
Maybe bumpsteer isn't what your experiencing. Or could be track drag length difference

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Zj steering linkage. Tracbar mount isnt too exagerated from stock if at all.

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  #12  
Old September 8th, 2020, 18:38
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Re: alignment?s

Quote:
Originally Posted by Tim_MN View Post
Stock, the front/rear wheelbase left/right difference is 10mm longer on the right side to offset crowned pavement.
Holy smokes thats much more than ide have thought, much appreciated Tim!
This is adjust by control arms correct?



Evan Im not sure if that geometry change is built into the Cs, mine read almost identicle for caster maybe .4 difference if that.

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  #13  
Old September 9th, 2020, 17:29
Evan03 Evan03 is offline
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Re: alignment?s

Yeah idk but I do know I've seen guys give advice like set drivers side to 5 and passenger 6.5. Im like yeah and make sure you twist the pressed in tubes to accomplish that.

Stripped my 30 did my own uper and lower brackets set the frame side brckets as true s I could. Still ended up alittle off. She drives straight doing 75 doesnt pull or anything. So I'd have to belve 3/8" one way or the other probably doesn't matter is most likely just some engineer making a pay check.

I see a .5 - 1deg from side to side but I think its more from how its sitting slightly out of level,though when setting castor i make an attempt to level everything.
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  #14  
Old September 9th, 2020, 17:40
Evan03 Evan03 is offline
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Re: alignment?s

just noticed the picture.

My first question whts good about zj steering it appears to be some as stock xj.

I notice a pretty substantial difference in track bar and drag link. Though parralell the length difference may be great enough that the two bars swing in different arcs(paths)

Shit i just measured stock xj drag link is 5" longer than track bar.


I wonder if track bar bolt on the axle side is wobbled out and allowing it bump back and forth feeling like bump steer.
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  #15  
Old September 9th, 2020, 18:49
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Re: alignment?s

Quote:
Originally Posted by Evan03 View Post
just noticed the picture.

My first question whts good about zj steering it appears to be some as stock xj.

I notice a pretty substantial difference in track bar and drag link. Though parralell the length difference may be great enough that the two bars swing in different arcs(paths)

Shit i just measured stock xj drag link is 5" longer than track bar.


I wonder if track bar bolt on the axle side is wobbled out and allowing it bump back and forth feeling like bump steer.
zj steering was an upgrade from the stock xj tie rod when I was going up smaller tire sizes. Its a solid tie rod vs the stock hollow toothpick. It will be replaced eventually but it works for now. Definitely worth carrying for a spare for anyone keeping stock geometry/mounting.


The trac bar axle side bolt is a good thought. I have had it marked with permanent marker to make sure nothing moved during my moab trip, nothing shows movement, but I will pull the bolt to check for sure. If Im lucky it is wallowed haha, SFR has a bracket Ive been wanting to upgrade to.
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