Help! Alignment Question

[Tyler James Inc]

Notice your vehicle only had a .2 thrust angle. And yours was aligned using a Snapon/John Bean aligner, that other one was done with equipment from St. Louis. :hunter:

Could you elaborate on this? I really only know enough about alignments to get me by. I am not familiar with thrust angle. It's under the rear category- is that related to me not having fixed my panhard yet? I know my rear axle isn't centered because of it.
Is the Snap-On/John Bean better?
Edit-
Just Googled it. Sounds like I happened to guess right on that. Need [MENTION=28464]eimkeith[/MENTION] stat.
Also, what do you mean it only had a .2 thrust angle? Shouldn't it have 0?

 

[jkeith.w]

sup?


seriously, though - Snap-On, Hunter, whatever - there's a misconception about the profession; alignment shops have to churn out alignments all day long - it's the business model. And whoever used the term 'certified' - certified by whom?


in my experience, you need an indy shop with decent equipment and a guy who cares to get a good alignment (- and you shouldn't expect him to solve worn bushing issues in the rear, either.)

 

[jkeith.w]

Also, what do you mean it only had a .2 thrust angle? Shouldn't it have 0?

yep. as close to zero as possible.

 

[IBallEngineer]

Could you elaborate on this? I really only know enough about alignments to get me by. I am not familiar with thrust angle. It's under the rear category- is that related to me not having fixed my panhard yet? I know my rear axle isn't centered because of it.
Is the Snap-On/John Bean better?
Edit-
Just Googled it. Sounds like I happened to guess right on that. Need [MENTION=28464]eimkeith[/MENTION] stat.
Also, what do you mean it only had a .2 thrust angle? Shouldn't it have 0?

OK, I'm a little biased. I sell these things for a living and I DO believe ours is better. We did invent the imaging technology after all. But I could align a car on a machine from St. Louis. Yes Zero would mean your rear axle has equalized rear toe, nothing to do with centering(offset). Basically Zero Thrust angle would mean the rear wheels are parallel to the chassis, sort of. Because you could be toed in or out equally and still have zero thrust, just not zero toe.

 

[Tyler James Inc]

OK, I'm a little biased. I sell these things for a living and I DO believe ours is better. Yes Zero would mean your rear axle has equalized rear toe, nothing to do with centering(offset).

Haha gotcha.
But the rear axle has no toe adjustment, and there is no reference points set to the chassis, correct?
So really, it kind of does have a lot to do with the axle being not centered- know what I mean?
That's why my steering wheel is now clocked a hair to the left- notice the toe adjustment happens to match the thrust angle difference? My steering wheel was straight when I took it in to him. Using the offset rear axle as part of the equation, he aligned my steering with the rear axle. I was wondering why my steering wheel is clocked after the alignment- now it makes sense!

 

[Tyler James Inc]

It doesn't match the toe, but the toe initially had a difference of -.10 and .20. That's based off the rear axle reference points, right?

 

[JayRolla]

Haha gotcha.
But the rear axle has no toe adjustment, and there is no reference points set to the chassis, correct?
So really, it kind of does have a lot to do with the axle being not centered- know what I mean?
That's why my steering wheel is now clocked a hair to the left- notice the toe adjustment happens to match the thrust angle difference? My steering wheel was straight when I took it in to him. Using the offset rear axle as part of the equation, he aligned my steering with the rear axle. I was wondering why my steering wheel is clocked after the alignment- now it makes sense!

Your steering wheel should still be straight. He could have fixed that with toe.

How can he align steering to rear without rest adjustment?

 

[Tyler James Inc]

Your steering wheel should still be straight. He could have fixed that with toe.



How can he align steering to rear without rest adjustment?

I'm not sure what that last sentence was asking, but yeah- the steering wheel alignment is adjusted through toe adjustment. Thats not really the point though. With the rear axle offset, it will see one side of the rear having toe-in, the other toe-out. In reality, the rear has no toe, but the whole chassis is cocked a little.

 

[IBallEngineer]

I'm not sure what that last sentence was asking, but yeah- the steering wheel alignment is adjusted through toe adjustment. Thats not really the point though. With the rear axle offset, it will see one side of the rear having toe-in, the other toe-out. In reality, the rear has no toe, but the whole chassis is cocked a little.

Yeah, it is NOT offset, it is out of square, big difference really. Offset is measured as linear measurement, say 4 mm of positive offset would indicate the axle is shifted to the right 4 mm. Thrust angle/Out of square is measured in degrees, based on the TOE angle, so since you are toed in.3 on the left, and toed OUT .1 on the right the net effect is .2 total toe, but since it is MORE positive than negative by .2, that is your thrust angle.

So let's say your right side control arm bushings are worn out and the right side of the axle is shifted REARWARD, this would cause the Left side to angle in(Positive toe). This is what the thrust angle is. Or put another way, if you drew a line along the center line of the axles, and measured the angle against the frame, it is .2 from 90 degrees.

Again, in reality the rear DOES have toe, just not toe adjustment.

OH and yes, the front toe angles are measured in comparison to the rear reference on all thrust angle alignments. If they were to select TWO wheel alignment, that would not be true.

 

[Tyler James Inc]

We're really just talking in circles here.
I'll center my axle and get it back on the rack- I'll bet you real dollars my thrust angle will be back to 0- without touching anything else(bushings, etc).

 

[d0nkeyxpunch]

The technicians said my rear bushings on the control arms are fine and not worn. What could be causing the difference from left and right toe in the rear? Currently it is 0.4 and -0.32. My total rear toe is 0.08 and thrust angle is 0.36.

 

[jkeith.w]

The technicians said my rear bushings on the control arms are fine and not worn. What could be causing the difference from left and right toe in the rear? Currently it is 0.4 and -0.32. My total rear toe is 0.08 and thrust angle is 0.36.

You've either got a bent rear axle (doubt it), bad rear wheel bearing, or bad bushings in the control arms - the axle isn't perpendicular to the chassis centerline, - and it's moving, based on those toe measurements.

The rear axle looks like it's changing thrust angle just by roll compensating (look at before & after toe measurements. The camber values don't change, and the total toe back there doesn't either). That would say bushings to me...

How did the tech determine the bushings are good? Visual inspection?


Sent from my iPhone using Tapatalk

 

[d0nkeyxpunch]

You've either got a bent rear axle (doubt it), bad rear wheel bearing, or bad bushings in the control arms - the axle isn't perpendicular to the chassis centerline, based on those toe measurements.

How did the tech determine the bushings are good? Visual inspection?


Sent from my iPhone using Tapatalk

Yeah visual inspection. Will my tires wear out very fast? I just spent a good amount of money on KO2s. lol Also, how do I know if my rear wheel bearing is bad? I don't feel any vibrations, no noises, and no leaks.

 

[jkeith.w]

Yeah visual inspection. Will my tires wear out very fast? I just spent a good amount of money on KO2s. lol Also, how do I know if my rear wheel bearing is bad? I don't feel any vibrations, no noises, and no leaks.

I wouldn't be worried about a bearing if there's no noise, vibration, or leaks.

And from what I'm seeing there, neither wheel is moving independently of the other, toe or camber-wise.

I still suspect bushings.


Sent from my iPhone using Tapatalk

 

[IBallEngineer]

We're really just talking in circles here.
I'll center my axle and get it back on the rack- I'll bet you real dollars my thrust angle will be back to 0- without touching anything else(bushings, etc).

I'll bet you Donuts you are right!

 

[jkeith.w]

I'll take that bet.