Alignment specs for 5" long arm kit?

[jeeeep]

That's how the rear axle center is compared to your front axle center. But on a Jeep it's tricky because of the way the track bar causes the thrust angle to change over every single bump as the axle moves. If each axle is centered perfectly, they still move as soon as you start driving so it's pretty useless to measure it on a Jeep.

I thought it was the parallel relationship between the front and rear axle, the side-to-side movement won't matter if the axles are parallel.

But, if the thrust angle is off it can have an impact on whether the vehicle feels like it's going straight or off to one side.

 

[DaBank]

Why would the toe not be the same from left to right?
What adjustments are needed to get the thrust angle correct?
Is my toe in 1/16?

 

[Cousin Clyde]

Yea OP, as @CalSgt referenced, the DIY alignment thread is a great way to set everything up. Once I do everything in the thread, I just drive a bit and make small adjustments until the jeep feels the way I want.

Here’s the JK one, assuming you still drive a 2010 JK

Basic Do-it-Yourself Jeep JK Wrangler Front End Alignment

If you've just installed a brand new lift on your Jeep JK Wrangler and are wanting to get it aligned, there are a few things you should know before you take it to a shop and pay to have it done. First off, you should know that thanks to the new steering design on the Jeep JK Wrangler, very...

www.wayalife.com

Edit: I see you have a 2017 JK now

 

[DaBank]

I just had a new complete front axle installed under warranty.
I have a 5" long arm kit with adjustable control arm's.
I need to adjust the front arm's to get around 5 degree caster.
Attached is the current alignment after they installed the front axle at the dealer. Do I adjust the upper or lower front arm's? Do I make the arm's longer or shorter? What would be a good guess on how many turns I should do?

I been told to have the toe set 1/16 to 1/8, what would 18° toe translate to?

As far a the rear alignment the toe is off side to side?
What should the thrust angle be?

Thank you.
Frank

 

[jeeeep]

I just had a new complete front axle installed under warranty.
I have a 5" long arm kit with adjustable control arm's.
I need to adjust the front arm's to get around 5 degree caster.
Attached is the current alignment after they installed the front axle at the dealer. Do I adjust the upper or lower front arm's? Do I make the arm's longer or shorter? What would be a good guess on how many turns I should do?

I been told to have the toe set 1/16 to 1/8, what would 18° toe translate to?

As far a the rear alignment the toe is off side to side?
What should the thrust angle be?

Thank you.
Frank

if you want to adjust caster, this will help you better understand the dynamics of upper/lower control arms and pinion angle:

https://project-jk.com/jeep-jk-tech...o-i-measure-it-and-how-does-it-affect-my-jeep

what size wheel/tire are you running? NVM, saw your 1st post.
18* i thought was close to 1/8 but I really don't know

 

[Cousin Clyde]

What should the thrust angle be?

Same as last year:

 

[dchew]

I been told to have the toe set 1/16 to 1/8, what would 18° toe translate to?

Note it is 0.18 degrees, not 18 degrees. I won't bore you with the math. It depends on your tire size. Well, really the point where you are measuring toe. If you are doing that on the tread-face of your tire, then tire size is a pretty good approximation. 0.18 degrees is:
35" tire: 0.110"
37" tire: 0.116"
38" tire: 0.119"
40" tire: 0.126"

All a little less than 1/8" (except 40" tire), which is why you hear 1/16 and 1/8 used all the time.

Dave

 

[DaBank]

Would I adjust the front arm's longer or shorter to get to 4.5 caster? Would I be adjusting the top or lower arms? Thanks

 

[DaBank]

Note it is 0.18 degrees, not 18 degrees. I won't bore you with the math. It depends on your tire size. Well, really the point where you are measuring toe. If you are doing that on the tread-face of your tire, then tire size is a pretty good approximation. 0.18 degrees is:
35" tire: 0.110"
37" tire: 0.116"
38" tire: 0.119"
40" tire: 0.126"

All a little less than 1/8" (except 40" tire), which is why you hear 1/16 and 1/8 used all the time.

Dave

So I am within 1/16" to 1/8" toe. Yes 0.18 degrees.

 

[DaBank]

I measured my rear axle and the passenger side is sitting 1/4 closer to the front. Would that translate to - 0.42 shown on the alignment?
I have a 8 arm long travel kit with adjustable front upper and lower arms but the rear uppers are fixed and the rear lower are adjustable. Would it be better to extend the rear lower passenger side or to shorten the rear lower driverside?

 

[dchew]

I measured my rear axle and the passenger side is sitting 1/4 closer to the front. Would that translate to - 0.42 shown on the alignment?

Pretty close. I'm not sure what the track is of your setup. Depends on your backspacing, axle length, spacers, etc. I think stock is 61.9". If I use 64", then:


Dave

 

[dchew]

Sorry probably should not divide the axle by 2. I’m not sure how Thrust Angle is defined.

Edit: If I understand the definition correctly, I get 0.23 degrees using track 64" and your 1/4". Their 0.42 deg would be 0.47"

I'm guessing that 1/4" is difficult to measure accurately.

 

[DaBank]

Pretty close. I'm not sure what the track is of your setup. Depends on your backspacing, axle length, spacers, etc. I think stock is 61.9". If I use 64", then:
View attachment 403087

Dave

Dave thank you!!
The axles are oringal. I have a 2017 Jeep JKU Rubicon Recon.
I just checked my wheels and they are 17x9 with 4.53 back spacing, no spacers. Not sure if tires make a difference but I have Cooper SST 37x12.5x17.
I appreciate your help!!
Frank

 

[DaBank]

Yea OP, as @CalSgt referenced, the DIY alignment thread is a great way to set everything up. Once I do everything in the thread, I just drive a bit and make small adjustments until the jeep feels the way I want.

Here’s the JK one, assuming you still drive a 2010 JK

Basic Do-it-Yourself Jeep JK Wrangler Front End Alignment

If you've just installed a brand new lift on your Jeep JK Wrangler and are wanting to get it aligned, there are a few things you should know before you take it to a shop and pay to have it done. First off, you should know that thanks to the new steering design on the Jeep JK Wrangler, very...

www.wayalife.com

Edit: I see you have a 2017 JK now

I have used the DIY thread in the pass for toe, steering wheel.
My thrust angle has been off since the Jeep has been lifted but now a little more. Before taken the Jeep to have the front axle assembly warrantied I put on all new heim joints and made sure the control arm's are equal length. I am 100% they are equal and now my thrust angle is twice as bad.
On the rear, my long travel kit has weld on frame brackets and doing some measurements one side looks like it is a little over 1/8" closer to the axle than the other side.
My rear uppers long arms are fixed length and the lowers are adjustable so I can only adjust the lowers. So it looks like I need to adjust the lowers not equal to correct the thrust angle unless I am missing something?

 

[dchew]

I'm pretty sure the stock recon wheels were 5.5" backspacing for a track of 61.9." If your wheels are now 4.5", then that adds 2" to the track and you are at 63.9, almost exactly what I guessed. I'm only using the track spec because that's the only way I can use the 1/4" dimension you gave me to back calculate your thrust angle. Using your 1/4", that gives a thrust angle of 0.22 degrees which is within their specification.

If it was me, I wouldn't change anything. Remember, these solid axles can move all over the place; it's just the way track bar + 4 CA suspension works. According to your most recent 1/4" measurement, you are within the 0.25 degrees they have as an acceptable range. You can chase 1/4" here, 1/8" there forever.

I'd be happy to help you calculate whatever you need, but I suspect you are chasing something that doesn't matter too much.

Dave

 

[Cousin Clyde]

@DaBank, see post below from WJCO regarding thrust angle.
As long as you have completed all of the steps in the alignment write-up, you should be good to drive your jeep. Just keep an eye out for tire wear and excessive vibrations.

I don’t mean to oversimplify your issue, but you’ve been doing the deal for 10 years now, yea? You know what works on a JK and what doesn’t.

That's how the rear axle center is compared to your front axle center. But on a Jeep it's tricky because of the way the track bar causes the thrust angle to change over every single bump as the axle moves. If each axle is centered perfectly, they still move as soon as you start driving so it's pretty useless to measure it on a Jeep.

 

[DaBank]

@DaBank, see post below from WJCO regarding thrust angle.
As long as you have completed all of the steps in the alignment write-up, you should be good to drive your jeep. Just keep an eye out for tire wear and excessive vibrations.

I don’t mean to oversimplify your issue, but you’ve been doing the deal for 10 years now, yea? You know what works on a JK and what doesn’t.

I bought the Jeep new in 2018 and had it lifted at 200 miles and now it has 50k miles. Jeep just installed a complete new front 44 axle under warranty. When they diagnosed the axle was bent the alignment showed the thrust angle was .20°. Before they installed the new axle I removed and installed all new heim joints in my contorl arms and I adjusted them even.
They did an alignment after the installing the new front axle and did not adjust any of the arm's.

So now that my thrust angle is at .42° vs .20° I double checked my rear arms and they are even, then I checked my welded on frame mounts for my lower rear (only the rear lowers are adjustable) arms and one mount is 1/8" welded on closer towards the rear axle.
So it looks like I need to adjust one side longer if I am going to get my thrust angle at or near zero.

My 1st question do people with lifted Jeeps and everything done correct getting their thrust angle to zero?

My 2nd question based off @dchew numbers that .42° is close to 1/2" would be how many full turns of my contorl arm would equal to .42°/ 1/2" ?

My 3rd question is my front caster is 3.3° and how many full turns on my front upper contorl arms would get me to 4.5° caster?
I would like to make these adjustments myself to get close to the correct number's because Jeep will recheck the numbers for me after I make the adjustments (they won't adjust the arms) and then I will have a baseline if I need to make anymore adjustments.

Thanks again for all the suggestions/input.
Frank

 

[jeeeep]

do a youtube search for thrust angle, rear axle alignment.

if the rear brackets are an 1/8 inch off, that's a starting point but you'll want upper and lower control arms to avoid changing pinion angle.

I'd say most leave it alone unless there are obvious issues or like me, OCD (also the reason I opted for control arms all around).

each manufacturers control arms are different, you'll need to reach out to the manufacturer or search for those specific control arms adjustment beginning points (the same arms on different Jeep will adjust differently); personally, I'd turn them then check the angle to figure out how many turns for 1 degree of change. It's a process but works and will be for your specific build.

Download the manufacturer installation manual, they usually list control arm adjustment starting points.

 

[dchew]

how many full turns of my contorl arm would equal to .42°/ 1/2" ?

It's best to just measure the starting arm length and turn until you get the added length you want using that 1/2" figure.

If you can find the threads used on your adjustable ends, just divide the thread pitch by 2 and that would give you an approximate answer to how many turns equals 1/2". See the screenshot below. I'm assuming your arms have fine threads. The thread pitch is TPI, threads per inch. 1/2" is half that number.


I say approximate because all your arms descend at some angle, so that calculated result will move the axle a little less. But even at a 30 degree down angle you will only be 15% less. On the other hand, your CA mounts are inside your track (tires) by a good amount, so that makes your change in CA length move the axle more at the wheels than the arm's change in length. There is too much inaccuracy in all those measurements to get any better estimate than lengthen (or shorten) the arm by 1/2".

Nice Jeep!
Dave

 

[DaBank]

I have not adjusted anything yet.
On the front I was checking my Caster angle using the front axle flat bases. The level is saying 92.2°. I tried the top of the ball joints but the numbers are all over the place.
My alignment print out shows my Caster is at 3.3° and the DIY Alignment link says that the level should show 92° on the axle flat base and that would equal about 4.2° of Caster?