argh, alignment=good, still pulls

[gavin]

been getting frustrated by this for a while...
have a good hard pull to the right. Assumed alignment, so went and got alignment a few months back.
still had a hard pull.

about a month ago, found an upper control arm bolt was loose; tightened it.

got alignment done again today; all within specs. Still effin pulling hard to the right.

not a tire issue; rotated tires multiple times with no change.
checked, re-checked, and triple-checked tire pressures, all the same.

Now, on a previous alignment print-out I received, it showed the "thrust," which is apparently how "straight" the rear axle is to the frame, from what I could find online.
The last one I had, showed a thrust of 0.10*

this alignment shop didn't print out that, only toe, camber, and caster from the front.

Would a thrust of 0.10 degrees cause a hard pull to the right? this would mean something with the rear axle is effed up, correct?

 

[yellowford]

You might want to check your right caliper as well to see if it is sticking giving you the pull to the right.

 

[gavin]

ah... forgot to mention that.

I've also swapped rotors around, front and rear.

none of the corners have any excessive drag and all rotate (relatively) easily.

 

[gavin]

I think I may have found my answer after much more googling.

The angle between the thrust line and centerline. If the thrust line is to the right of the centerline, the angle is said to be positive. If the thrust line is to the left of center, the angle is negative.

so with a positive thrust angle, would mean the rear axle is pointing towards the right side of the vehicle, causing a right-hand pull.

just not sure if a wimpy 1/10 of a degree would cause it to be as bad as it is?


guess this just gives me more motivation to get new gears and work on regearing my original axles.

 

[dogfriend]

Yes, ideally the thrust angle would be zero. One quick and dirty measurement is to straighten out the steering and then measure from the front wheel to the same spot on the rear wheel. Then repeat the same on the other side. The two sides should be the same, if not, then something has moved at the rear axle.

 

[storlied]

Haven't you done leaf work? Perhaps something came loose on one side and shifted? ..Is it possible the axle might be shifting only when you take the turn? These trucks do some odd things sometimes..

 

[gavin]

Haven't you done leaf work?

not in years.

Perhaps something came loose on one side and shifted?

there's nothing that can "shift" except for the leaf packs. And for those to "shift" the u-bolts would have to be very loose, which would cause a lot more drivability issues.

..Is it possible the axle might be shifting only when you take the turn?

no, becuase the pull wouldn't always be to the same side if something was shifting back and forth.


probably just somethin wrong with this junkyard axle. Always drove straight before I swapped axles. So it's just incentive to get my old axles regeared to 4.56

 

[dogfriend]

Ive seen enough F150's and E150's that are crabbing (rear wheels not behind the front wheels while driving down the road) to believe that some of them must come from the factory that way.

I would try to establish that the axle is perpendicular to the centerline of the truck. Could it be possible that the spring pad has slipped relative to the spring?

 

[gavin]

Ive seen enough F150's and E150's that are crabbing (rear wheels not behind the front wheels while driving down the road) to believe that some of them must come from the factory that way.

I would try to establish that the axle is perpendicular to the centerline of the truck. Could it be possible that the spring pad has slipped relative to the spring?

one of the first things I checked was to see if maybe someway, somehow, one of the leafpacks bolts wasn't centered in the spring pad anymore, but there definitely is no gap between the pads and leaf packs.

this is a junkyard axle I bought... crap... I can't remember how long ago now? Last summer? since my front diff decided to get the hole in it.

well luckily, I never turned in my original axle as a core charge, so I still have it. And I want to upgrade to 4.56's anyway. And since I can't afford to pay someone to regear my axles, and they're not in the truck anyway, makes it perfect so I can take my time and figure out how to set gearsets myself.

 

[Brandon@BTF-fab]

to get rid of the pull to the right, you can either add caster to the right, or take away some caster on the left, using your alignment cam adjusters on the upper arms. I betcha it's alignment. I've argued w/ alignment shops so many times when they said it's "within spec" and it still pulls. thier argument was that caster is a non-wearing angle so it doesn't matter.:thumbdwn:

just in case you're not familiar, caster is how far tilted back the top of the spindle is compared to the bottom.

 

[reserved50]

swap the tires on the left side with the right
check the temperature of the calipers after a drive and see if they feel the same, compare fronts to each other
go to another alignment shop and get a before and after printout and why it pulled
a bad rack and pinion would be last bet

 

[gavin]

swap the tires on the left side with the right
check the temperature of the calipers after a drive and see if they feel the same, compare fronts to each other
go to another alignment shop and get a before and after printout and why it pulled
a bad rack and pinion would be last bet

not a tire issue; rotated tires multiple times with no change.
checked, re-checked, and triple-checked tire pressures, all the same.

rack and pinion was also replaced a couple weeks ago.
no tire drags more than the others when rotating them by hand.

I've had the pull through 3 different alignments, with 3 different shops. None of them "guarantee" or "warranty" the work due to it not being completely stock suspension.

I just don't know exactly when the pull started, but I know I've had it for a long while. It's very possible it started with the axle swaps.

to get rid of the pull to the right, you can either add caster to the right, or take away some caster on the left, using your alignment cam adjusters on the upper arms. I betcha it's alignment. I've argued w/ alignment shops so many times when they said it's "within spec" and it still pulls. thier argument was that caster is a non-wearing angle so it doesn't matter.:thumbdwn:

just in case you're not familiar, caster is how far tilted back the top of the spindle is compared to the bottom.

alignment numbers have ALWAYS been within OEM specs, including caster.


edit: so I did the swap around June '08. Found some previous alignment printouts. Since I did the swap, the thrust angle has varied from -0.04* to 0.11*
not that I'm really sure what exactly that means. I guess it depends on how, exactly, the thrust angle is measured. Since the front axle is obviously not moveable, the thrust angle shouldn't change unless something happens with the rear axle, suspension, or frame, right?

the most recent printout that got specs from all 4 corners.

 

[etc]

Make sure the alignment techs set your steering wheel before doing the alignment.

 

[reserved50]

I asked about the tire rotation because some people assume they are supposed to be rotated front to back when checking for pull.

Spinning the wheels isnt enough, sometimes its better to compare heat readings off the calipers, wheels, rotors etc.

It seems like the rear axle wants to steer to the left by looking at the toe making the front end "pull" to the right. The thrust angle means the back axle is not inline with the front, that would not cause a pull by itself but your toe readings are not equal. Like a few have mentioned your leaf springs might be twisted or your axle or frame in that order.
Im guessing if everything else is fine its not a hard pull but a fairly obvious one?

 

[gavin]

I asked about the tire rotation because some people assume they are supposed to be rotated front to back when checking for pull.

Spinning the wheels isnt enough, sometimes its better to compare heat readings off the calipers, wheels, rotors etc.

It seems like the rear axle wants to steer to the left by looking at the toe making the front end "pull" to the right. The thrust angle means the back axle is not inline with the front, that would not cause a pull by itself but your toe readings are not equal. Like a few have mentioned your leaf springs might be twisted or your axle or frame in that order.
Im guessing if everything else is fine its not a hard pull but a fairly obvious one?

it's a very hard pull. For as hard as the pull is, if it was caused by brakes it would be obvious when rotating by hand.
I rotate my tires both front to rear and left to right. So the pass front and dri rear are swapped, then dri front and pass. rear.
I also have a 5th full size spare which I rotate.
it does NOT change with the tires.
you also mention the toe readings aren't equal... huh? This print out shows that the toe is 0.15* on both sides.

Make sure the alignment techs set your steering wheel before doing the alignment.

ummm.. it's not that the steering wheel is off-center. The steering wheel does try to center itself, but then pulls. Which means it has nothing to do with the steering wheel not being centered.

 

[Brandon@BTF-fab]

add more caster on the right, and/or less caster on the left....I bet you it will get rid of the pull, OEM specs or not.

 

[V8BoatBuilder]

Do you have any bump steer? Improper caster can effect that, too.

Caster is only adjustable on the pass side. Mark your upper A-Arm with a paint pen so you can go back to the current setting, and then try adjusting it. You've got nothing to lose.

 

[gavin]

Do you have any bump steer? Improper caster can effect that, too.

Caster is only adjustable on the pass side. Mark your upper A-Arm with a paint pen so you can go back to the current setting, and then try adjusting it. You've got nothing to lose.

just curious how caster would affect a pull.
since it, essentially, only rotates the knuckle forward/backward.

and which way would I need to adjust it... adding caster would mean making the knuckle lean more towards the front of the vehicle?

 

[V8BoatBuilder]

And FYI,

On my last alignment "check" at Firestone, the "Thrust Angle" was 0.30.
My Caster, however, is at 2.2 on the left, and 1.2 on the right. Toe is 0.18 left, 0.20 right. Camber is 0.1 left, -1.4 right.

By those numbers, the truck is WAY out of spec except for toe, but I did not have any serious drivability issues at the time.

That was with the Superlift up front and an SOA in the rear. (The alignment is AFU right now, but that's a different story)

 

[V8BoatBuilder]

This was taken from: http://www.familycar.com/alignment.htm

When you turn the steering wheel, the front wheels respond by turning on a pivot attached to the suspension system. Caster is the angle of this steering pivot, measured in degrees, when viewed from the side of the vehicle. If the top of the pivot is leaning toward the rear of the car, then the caster is positive, if it is leaning toward the front, it is negative. If the caster is out of adjustment, it can cause problems in straight line tracking. If the caster is different from side to side, the vehicle will pull to the side with the less positive caster. If the caster is equal but too negative, the steering will be light and the vehicle will wander and be difficult to keep in a straight line. If the caster is equal but too positive, the steering will be heavy and the steering wheel may kick when you hit a bump. Caster has little affect on tire wear.