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Shop adjusted my trackbar during alignment?

gagamaggot

gagamaggot

NAXJA Forum User
Location
Colorado
I dropped off the Jeep this morning for an alignment because I just got new tires.

The shop just called to say it was done and the guy says they had to adjust my trackbar during the alignement.

I have a JKS under there and I had the axle centered.

Any ideas why they would have done this? I am taking a tape measure with me so I can check the axle.
 
The trac bar centers the axle. Maybe you didn't have it right.

I do my own alignments because most places around here won't even consider aligning my heep with the lift and everything.
 
I got the scoop when I got to the shop. I only expected them to do a front-end alignment, but they actually adjusted the trackbar to set the thrust angle. That is beyond my expectations from experience with other shops. The Jeep tracks better now than it has in years.
 
WheelinJR said:
maybe you can't read a measuring tape, haha jk

you might have been slightly off and they just fine tuned it for you...
Click to expand...

I was only .24 degrees (not inches) off on the thrust angle using a tape measure. The tech was pretty impressed how close it was.
 
just make sure they tightened the jam nut, i had a shop forget.
 
I'm impressed that they knew how to adjust the trackbar. Sounds like a shop to keep in mind for future work.

Last time I had a shop check the alignment they tried to sell me a 4-wheel alighment because it was a 4wd. The clerk wasn't real happy when I pointed out that was no way to align the rear wheels on this vehicle and they don't do anything different than they'd do for a standard front alignment. The customer next to me who had just paid for a 4-wheel alignment turned around and asked how they adjusted the thrust angle on his Wrangler as well.

You can actually do a really good alignment with nothing more than a couple of broom handles and a tape measure.
 
gagamaggot said:
I got the scoop when I got to the shop. I only expected them to do a front-end alignment, but they actually adjusted the trackbar to set the thrust angle. That is beyond my expectations from experience with other shops. The Jeep tracks better now than it has in years.
Click to expand...

I'm confused and it might be my own misunderstanding... But you're talking about them adjusting the front axle thrust angle?

Just to clarify; are they saying they modified the thrust angle of the front axle and in doing so had to modify the length of the track-bar?

Otherwise I can't imagine how the track-bar itself would modify the thrust angle as that should be accomplished with the control arms.
 
Adjustable track bar....

Thrust angle makes sure that all 4 wheels are "squared up" - its not an angle that's just related to the front axle - it lines up everything, front and rear.

By the sound of it, they probably only had to rotate the trackbar adjustment one rotation...
 
Last edited:
Disclose the name and location of this shop. I would drive a hundred miles to find such a well versed shop with the ethics that they seem to have displayed.
 
JNickel101 said:
Adjustable track bar....

Thrust angle makes sure that all 4 wheels are "squared up" - its not an angle that's just related to the front axle - it lines up everything, front and rear.

By the sound of it, they probably only had to rotate the trackbar adjustment one rotation...
Click to expand...

I'm aware of adjustable track-bars. The reason I was looking for clarity is due to the description of thrust angle in the FSM.

"THRUST ANGLE is the angle of the rear axle
relative to the centerline of the vehicle. Incorrect
thrust angle can cause off-center steering and excessive
tire wear. This angle is not adjustable, damaged
component(s) must be replaced to correct the thrust
angle."

Then there is is a graphic showing an axle turned radially to the vehicle centerline not shifted laterally. So using that description I would think adjusting the track-bar would which moves laterally the front axle wouldn't qualify as an thrust angle adjustment. To get the angle to change you would have to add or remove shims to the control arms (or spin the arms on aftermarket CA's).

Maybe this is the FSM's own definition of the term and the rest of the collective world has a slightly different interpretation of it. I probably should have just done some internet searching for other trusted sources to confirm or confuse the subject further. Just wanted to make sure that if I started using this term in conversation that I am correctly describing it.
 
Okay, but if your front axle isnt properly centered under the vehicle too, then your thrust angle wont be right either.

I understand what you mean about getting both axles parallel to each other (adjusting the control arms up front), but you also have to get them both lined up to the centerline of the vehicle.

Didnt mean to slight you on the adj trackbar comment, mis-read your understanding on it since you said "modify the length of the track bar".....

:)
 
Last edited:
From Tirerack:

The thrust angle is an imaginary line drawn perpendicular to the rear axle's centerline. It compares the direction that the rear axle is aimed with the centerline of the vehicle. It also confirms if the rear axle is parallel to its front axle and that the wheelbase on both sides of the vehicle is the same

We're both "right" - you're referring to getting both axles parallel, I'm referring to getting the wheelbase on both sides of the vehicle the same. :) apparently, its all a part of thrust angle adjustment....
 
No problem. Never worked as an alignment technician so I couldn't tell you with any certainty what is right or wrong.

I did a little searching and found in a SAE exam book they mention thrust line in addition to thrust angle. I'm going to paw thru it a little more and see if I can further clarify it.
 
Thrust angle may not be the right word, but essentially they adjusted it so the thrust line as drawn from the rear goes through the center of the front axle. So you want both the front and rear axles to be parallel, but also have their centerpoints lined up.
 
lawsoncl said:
Thrust angle may not be the right word, but essentially they adjusted it so the thrust line as drawn from the rear goes through the center of the front axle. So you want both the front and rear axles to be parallel, but also have their centerpoints lined up.
Click to expand...

Ultimately that is what I figured the gist of it was. But when they said thrust ANGLE and mentioned it was out .24 degrees that made me think otherwise. But I would assume the front axle was shifted laterally (not radially) off the center of the thrust line .24 degrees.

But I think we beat it out enough that I understand how or why a track-bar adjustment affected thrust angle in this situation.
 
My idea of thrust angle and thrust line is apparently different than this shop's idea of thrust angle and thrust line. I think thrust angle is the angle thats created between the front and rear axles. If they arent parallel there will be an angle that they are off, thats the thrust angle. Thrust angle or thrust line have nothing to do with the axles being centered under the vehicle so the trackbar can not be used to adjust the trust angle. The only way to adjust that on an XJ is by using caster shims.
Think of it like this, if your XJ is crabbing down the road, your trust angle is set wrong. Will a poorly adjusted trackbar cause your XJ to "crab", no it wont, your XJ will still track straight, Itll just track straight with your axle not centered.
I didnt explaing that very all, so anyway, glad it worked out for you.
 
mikeforte said:
Disclose the name and location of this shop. I would drive a hundred miles to find such a well versed shop with the ethics that they seem to have displayed.
Click to expand...
X2 I get tired of hearing about the shops that don't do quality work...and I even live in the same state as you.
 
mikeforte said:
Disclose the name and location of this shop. I would drive a hundred miles to find such a well versed shop with the ethics that they seem to have displayed.
Click to expand...

Stonum Automotive in Longmont, CO. They were recommended by a local 4x4 shop as willing to work on lifted rigs. I talked to them a bit and they will even work with adjustable CAs to adjust caster. Seem like a good, honest, locally-owned shop.
 
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