School Me On Front End Alignment?

[Nothing Special]

Gary Lewis wrote

....  And while you are reading what the FSM says, I wonder if the spec's are wrong.  Surely it should have said .025 degree, meaning from .035 to .085 degrees....

This is just me applying the sniff test, but a tolerance of +/-0.025 deg doesn't smell right.  +/-0.25 deg seems fairly tight to me.  A tenth of that?  No way.

And I wouldn't get worked up about the fact that the tolerance is twice (or even four times) the nominal.  The value of the nominal is very subjective based on where it's referenced from.  If the nominal was measured off the axle axis it would be 89.94 +/- 0.25 which wouldn't raise any eyebrows.

Still, it seems a little odd to me that they don't mind that much toe out.  I'm no expert, but it seems like I've always heard you want neutral to slight toe-in.  (And yes, I do get that if the tolerance was less than the nominal that it wouldn't allow toe-out, and I'm tearing my previous argument apart!)

[Gary Lewis]

I'll get pictures tomorrow, but I'm running a complete 1995 F350 steering setup.  That includes an F350 pitman arm and a tie rod connecting the front spindles.

On the +/-, I'm just going to ask for it to be set to .06 degrees of toe-in.  I'm thinking that is the main culprit in this, so I think going with the factory settings will be a good starting point.

[Gary Lewis]

Ok, here's a pic of the linkage from the front with the weight on it.  The red arrow shows the end of the track bar, and you can see the other end of it attached to the axle.  (And the Royal Purple bottle and the paper towels on the floor show my ill-fated attempt to cleaning drain the PS/hydroboost system.  )




And here's a shot from the other side.

[Nothing Special]

Definitely the one solid tie rod rather than the two angles rods of a TTB steering.  So you shouldn't have any of the wander issues Bill was thinking about.

As far as bump steer goes...

If you DIDN'T have the track bar, as the axle moved up it would move pretty much straight up (being controlled by just the leaf springs in that case).  In that case the distance between the right knuckle and the steering box would decrease, but since the drag link wouldn't magically shrink it would push the steering off to the right.  And as the suspension compressed the truck would tend to veer right (or the steering wheel would move to the left)

Since you do have a track bar which is pretty short and at a pretty steep angle, as the axle moves up it will actually move quite a bit to the right.  Moving up would shorten the distance between the right knuckle and steering box, but moving to the right would increase that distance.  From the geometry the increase would be greater than the decrease, so since the drag link won't magically stretch either, you should get some bump steer of the truck veering left (or the steering wheel turning to the right) as the axle comes up.

Eyeballing it I'd say you'll have less bump steer with the track bar than you would without.  And I don't see a good way to move mounting points to minimize it.  So I don't think I'd suggest any changes in this area.  But I think you will get some bump steer that you'll have to live with.


For what it's worth, solid axle leaf sprung vehicles never used to have track bars, and when Ford started putting them on F-350s a lot of people thought it was a terrible idea, that it would kill the suspension travel and the ride.  I have no personal experience, but I have heard that the track bar was a significant improvement in handling.  It must make the suspension stiffer (since the springs have to bend sideways or twist or something to let the axle move over as it moves up).  But evidently that's not a huge issue.

[85lebaront2]

Ok, as the axle moves up in relation to the frame, (a) the track bar will push the axle to the right and (b) the drag link will push the knuckle out at the front as in a right turn, BUT the track bar being shorter and at a greater angle will move the axle to the right further than the drag link, so the truck will pull to the left. This will be more evident at higher speeds as the tendency to pull to the left will result in the truck tilting slightly toward the right which will result in more downward motion on the right side moving the axle further to the right and giving more of a pull to the left.

Is it possible to lower the inner end of the track bar or raise the outer end so it is closer to parallel to the axle?

[Gary Lewis]

Thanks guys.  But lets see what the truck drives like when I get the toe-in set properly.  It may be quite livable at that point.  But that won't happen until next week at some point.

[ArdWrknTrk]

Gary,

Off topic but, why on earth didn't you just put the return line in a jug and start the truck?
You know it's going to pump until* it has no more.
Sure the line up to the booster would drain back, but you're not going to hurt the pump.
It's a core at this point anyhow.


*😖

[Gary Lewis]

ArdWrknTrk wrote

Gary,

Off topic but, why on earth didn't you just put the return line in a jug and start the truck?
You know it's going to pump infill it has no more.
Sure the line up to the booster would drain back, but you're not going to hurt the pump.
It's a core at this point anyhow.

  I didn't think of that, Jim.  But should have!  

[ArdWrknTrk]

Simple isn't always stupid.  

[Andre]

Gary,

I am with Bill and Bob on this issue, with the suspension going up and down, the axle will be pushed somewhere due to the stiff linkage you have added. Might be worth to install something similar to and shock absorber in the same place, this just to verify if it would change something.
Further more I find your angle from the pitman arm to the main steering shaft steep, sure you dont need to install a pitman arm that come down much more, to reduce the angle of the steering shaft?
Adjusting toe in is an option, zero is the worst, on my Bronco I decided to use some toe out, mainly for being a 4X4, and when that is selected the wheels will be pulled in to much.
Why have you not installed a steering dampener, this could reduce the bump part as well?

[Gary Lewis]

Andre - Thanks.  But when the shop checked the alignment they found it was actually toed out, so they dialed in the factory .06 degrees and it steers much better now.  No perfectly, but like it is a big, lumbering truck - which it is.  But I think it is what it is at this point - good but not perfect.

However, I don't have a steering damper, so will consider that.  Thanks!

[Nothing Special]

My first thought was that a steering dampener wouldn't affect bump steer.  That's just a function of the geometry.  If the axle moving up and down affects the distance between the two points where the drag link attaches you'll have bump steer, if not, you won't.

But on second thought, all the geometry means is that if that distance changes, then SOMETHING has to move.  If the easiest thing to move is the stuff on the axle, then you'll have bump steer.  But if a steering dampener makes it hard to move the stuff on the axle, then the stuff on the other end of the drag link will move.  That means the steering wheel will saw back and forth when you go over bumps.  That may or may not be objectionable, but it won't make the truck veer side-to-side (at least as much).

And that's actually the situation my Bronco had when I got it.  A big bump would make the steering wheel swing back and forth at least 45 degrees, but at least it stayed in the lane.  A dropped track bar bracket straightened things out for me, but the F-350 geometry doesn't seem as easy to tweak for that as the early Bronco steering is.

[Gary Lewis]

Interesting.  Hadn't thought of a steering damper causing the movement to go elsewhere.  But that makes sense.

I guess I'll drive it this way a bit more and see what I think.  Thanks.

[Les Kerf]

I had an 81 F-150 2wd that bump-steered; I went completely through the front end, replaced everything and had it properly lined up. Still no joy.

I finally replaced the wheel bearings in the REAR END (9 inch) and that cured the problem.

Not all steering issues are in the front end.

[Gary Lewis]

Les - You are right!  Since my last post in this thread I’ve removed two leaves from the rear spring pack and it really helped with the bump steer. Turned out someone had installed a spring pack with far more capacity than needed and there was NO flex. So on bumps the rear end was apparently stepping sideways.

So now the bump steer is pretty much gone, and I forgot to say that here. Thanks!

[FuzzFace2]

Les Kerf wrote

I had an 81 F-150 2wd that bump-steered; I went completely through the front end, replaced everything and had it properly lined up. Still no joy.

I finally replaced the wheel bearings in the REAR END (9 inch) and that cured the problem.

Not all steering issues are in the front end.

Les,
What made you change out the rear wheel bearings on that 9"?
Were they making noise and / or had a lot of play in them?

My 02 Durango when new you could feel the rear end "jump out" on you over bumps because the springs were new and stiff but now with 240K+ I don't feel it or I got use to it but would say it does not do it.

My 81 F100 really does not have bump steer but more of a wondering issue.
All the front end parts are tight and the kingpins maybe too tight as the steering wheel will not return center. When I have some time I want to run the kingpin reamer through the bushings and see if that helps.
Dave ----

[Les Kerf]

FuzzFace2 wrote

...
What made you change out the rear wheel bearings on that 9"?
Were they making noise and / or had a lot of play in them?

My 02 Durango when new you could feel the rear end "jump out" on you over bumps...

We have a long bridge (cleverly named 'The Long Bridge') near Sandpoint, Idaho; this bridge has concrete joints every ten feet or so that jostle even the best of vehicles.

When rebuilding the entire front end didn't help much, I got to noticing that the pickup seemed to twitch in the back end every time I hit one of those bumps. I jacked up the rear end and found a fair bit of play in the bearings ( not terrible, just not nice and tight). I never bothered measuring with a dial indicator, just went ahead and replaced both sides.

The Long Bridge is still a rough ride but at least I didn't have to worry about the pickup darting off in a different direction at every bump.