School Me On Front End Alignment?

Big Blue's 1995 D60 front end has all new components: ball joints; tie rods & ends; drag link; wheel bearings; etc.  And the steering box is a recently reman'd unit.  There seems to be no slack in the system, but the steering isn't as precise as I think it should be.

I don't really know how to describe it, but it has a bit of a mind of its own.  For instance, on some bumps it seems to steer itself.  And there are times when it over steers.  When you are on a wide road it isn't much of an issue, but when you are on a narrow road with a guard rail right on the edge you need to stay on top of it.

I've played with tire pressures to see if that would make much difference and it doesn't.  I've been running at 35 psi but tried 30 last week and 40 today, with little change.

So I've been doing some reading and this Tire Rack article speaks to a couple of those issues.  For instance, on negative camber it says:

What's the downside to negative camber? Negative camber leans both tires on the axle towards the center of the vehicle. Each tire develops an equal and offsetting "camber thrust" force (the same principle that causes a motorcycle to turn when it leans) even when the vehicle is driven straight ahead. If the vehicle encounters a bump that only causes one tire to lose some of its grip, the other tire's negative camber will push the vehicle in the direction of the tire that lost grip. The vehicle may feel more "nervous" and become more susceptible to tramlining. Excessive camber will also reduce the available straight-line grip required for rapid acceleration and hard stops.

On caster it says:

Increasing the amount of positive caster will increase steering effort and straight line tracking, as well as improve high speed stability and cornering effectiveness. Positive caster also increases tire lean when cornering (almost like having more negative camber) as the steering angle is increased.

What's the downside to positive caster? If the vehicle doesn't have power steering, a noticeable increase in steering effort will be felt as positive caster is increased. Other than that, the effects of positive caster are pretty much "positive," especially increasing the lean of the tire when the vehicle is cornering while returning it to a more upright position when driving straight ahead.

And on toe-in it says:

Toe can also be used to alter a vehicle's handling traits. Increased toe-in will typically result in reduced oversteer, help steady the car and enhance high-speed stability.

Now the question becomes where is it and should it change.  Here are the two pics I took of the computer's readout, and the reason I'm showing two is that it looks to me like the wrong vehicle was chosen the second time around.  The screen on the left, the first round, shows F350 1989-97.  The screen on the right shows F350 1997-99.  And the recommended ranges are different.

The correct mid-point settings from the first round and my current settings look to be:

Camber: 0 for recommended and BB is at .03 & -.1

Caster: 3.2 recommended and BB is at 3.2 & 3.4

Toe-in: .03 recommended and BB is at 0 and 0

Can those fairly small differences make it do what I'm seeing?

Gary, I may be totally out of line on this, but I still feel the angle of the track bar may be causing problems, particularly when one side of the suspension travels up or down, it will change the steering linkage geometry. For years the 4WD axles had a single "drag link" to the driver's side and a long tie rod from one spindle to the other.

From what I remember of your front end pictures your tie rods sit at a bit of an angle which means as the axle travels up toward the frame the toe will go from 0.3 in to a toe out condition while at the same time the track bar is pushing the axle left which will act on the whole system as if you turned the wheel slightly right (axle moves left but steering stays straight so the left movement of the axle pulls the left spindle in and pushes the right spindle out).

Even though BB isn't lifted, the tie rods are at a bit of an angle, maybe a dropped pitman arm might help and possibly a track bar pivot dropped to put it horizontal at rest. Not owning a 4WD, but having had a 1958 F100 with a "live" axle up front means I have dealt with some strange behavior, mine was lack of caster due to replacing the 223 6 with a 312 Y-block and as the front went lower the leaf springs de-arched and that truck would wander and even get the "death wobble". Once I put some caster in it (half length helper springs from Pep Boys on the back half of the front springs) the problem went away.

Darth is a 2WD, but since he has the Twin I Beam front suspension does have some of the quirks, not badly because I had a real good alignment done 26 years ago, lane keeping is excellent other than the fact that king pins have more turning resistance than ball joints (but they last a lot longer!) so he doesn't respond as easily to small changes in road angle as a car will.

Can you play with your AutoCAD program and maybe see what the suspension changes are as it travels both straight up and down and angled (as in a curve where BB will lean somewhat). Good luck with it!

Gary,
 Could you send me a picture or post a picture of your front end?  i have a 2007 Megacab that has/had bump steer and death wobble and have gone down the alignment rabbit hole..... you never mentioned your rag joint in the column...believe it or not that will cause some vagueness you are describing...more concerning is the bumpsteer situation.  You mentioned remanufactured box, what company? as all boxes are not created equally...ask me how i know..lol

What tires are you running and load rating?  What does tread look like? Any strange wear patterns?

I know with dodges factory setting is not optimal and actually most 3rd gen guys use thurens or carli settings...another words you may have to play a bit to dial in what is correct for your truck

you cannot adjust camber on a solid axle dana 60, and caster is done though shims, think about caster in terms like the wobbley wheel at the super market....your truck is stock correct?

track bar length and the bushing on frame side is where i would look close, on dodge that bolt needs to be torqued down 200+ft/lbs..also if that top hole or play in bushing gets "wallored" out a bit that might also be a source of vagueness/bumpsteer

How are bushings in your leaf springs?  The also help locate front axle, and if any play might cause axle to move a bit....only 1/16th of play in a few joints adds up quick

and as previously stated length of trackbar....being all stock i am not sure drop arm or location of draglink is a factor......but i can be wrong, and often am ..lol

When all else fails throw a stabilizer or 6 at it

I am gonna throw my two bits in then shut up. Normaly a rear wheel drive car/ pickup would not have 0 toe or toe out. A pickup like yours should have at least 1/8 toe in. I say that because as you are going down the road, the force will spread the wheels in the play in the parts( new or not, it still happens). If the toe is set at 0 sitting still, then the toe will be toe out at speed.

I dont want to get into the affects of caster, camber, akcerman angle, ect and how they affect each other.

Toe out will cause a wandering feeling and will cause the " bump steer " at speed.

Just my humble thoughts sir.

There's really nothing "stock" about Big Blue's front end.
Borgenson steering shaft, *Bluetop box, Saginaw pump, adjustable Pitman arm, SuperDuty springs with a SKY reverse shackle kit on a balljoint D60 from a mid '90's F350.

I'm sure I'm missing some details, but that's the jist of it.

You can adjust camber with balljoints. Heck, you can adjust kingpins with a torch.  💡


*= edit

Here's a picture Gary posted a few pages back that kind of shows the steering stuff.



I'm no expert, but my thoughts...

In that pic it looks like the drag link is angled down quite a bit from left to right and there's no track bar.  Is that correct? If so you'll definitely get some bump steer, with the tires turning to the right as the suspension compresses and to the left as it droops.  Adding a track bar that's parallel with the drag link would minimize that.  Or using a dropped pitman arm to bring the drag link closer to horizontal would minimize it as well.

Otherwise I'd probably try adding a little toe-in first.  That won't help with bump steer, but it could improve overall stability.

Caster and camber seem OK to my amature thinking.  I probably wouldn't mess with them.  But if I was changing anything there I'd go for a little more caster and a little negative camber.

85lebaront2 wrote

....  From what I remember of your front end pictures your tie rods sit at a bit of an angle which means as the axle travels up toward the frame the toe will go from 0.3 in to a toe out condition while at the same time the track bar is pushing the axle left which will act on the whole system as if you turned the wheel slightly right (axle moves left but steering stays straight so the left movement of the axle pulls the left spindle in and pushes the right spindle out)....

True for TTB, but not for a solid front axle.  Toe-in won't change because the knuckles are always the same distance apart (fixed by the axle housing) and the one-piece tie rod is always the same length.

I think he has some pictures before the winch bumper install that do a good job showing the SKY brace across the frame horns and all the steering.

Though, those may be up on the lift and only show it in full droop.

Guys - Thanks for all the input.  I certainly appreciate it.  But I think I may see what the problem is, and it fits with what Steve is saying - toe-in.

The factory specs from the 1995 FSM are below, and I've highlighted the toe-in specs, which are supposed to be between .035 and .085 degrees, with .06 being the center of that.  But Big Blue is sitting right on 0.

Using CAD, on 33" tires having both of them toed in at .06 degrees, which I think is what is meant, will put the front inside edges of the tires .060" closer than straight ahead.  So basically 1/16".  Am I doing that correctly?

That fits with Tire Rack's statement of "Increased toe-in will typically result in reduced oversteer, help steady the car and enhance high-speed stability."  And it fits with Steve's statements of "If the toe is set at 0 sitting still, then the toe will be toe out at speed" and "Toe out will cause a wandering feeling and will cause the "bump steer" at speed."




So my plan is to have the toe-in set to .06 degrees and see what that does.  But are there other questions that y'all have?  Did I miss something?

Bob - I see you just replied, and Jim replied to your post.  But there is a track bar on the back of the axle on the passenger's side, as shown below.

What I don't have on is the factory sway bar, and that's because taking the sway bar off the TTB's helped the ride significantly, and I'm looking for ride quality.  Once I get the steering sorted then I could put the sway bar on and see what it does.

Gary Lewis wrote

....  Bob - I see you just replied, and Jim replied to your post.  But there is a track bar on the back of the axle on the passenger's side, as shown below.

Not seeing the track bar and the drag link at the same time it's hard to picture exactly what will happen as the suspension cycles.  It looks like the track bar is probably pretty close to parallel with the drag link.  But it also looks to be a lot shorter.  So I'm not sure what that will do with bump steer.

The issue (obviously?) is that the drag link will push the tie rod back and forth as the suspension cycles and the track bar will push the axle back and forth.  If the tie rod moves the same distance as the axle there won't be any steering input.  If they move different amounts there will be bump steer.

With the different lengths the movement can't be the same through the entire range of travel.  But is it pretty close in the normal range of travel?  That's what I can't wrap my head around without seeing it better.

But this is all talking about bump steer, which is one issue you mentioned.  But it won't affect wander which is priobably your bigger concern.

Gary Lewis wrote

What I don't have on is the factory sway bar, and that's because taking the sway bar off the TTB's helped the ride significantly, and I'm looking for ride quality.  Once I get the steering sorted then I could put the sway bar on and see what it does.

I wouldn't think that adding the sway bar would make a lot of difference in the steering unless you feel the truck swaying side to side.  If the truck is moving around quite a bit that means you could be getting "bump steer" even if there aren't any bumps.  But I'm guessing Big Blue isn't swaying around noticeably.  Sure, you could put it on to verify.  But I'd be surprised if it would affect your steering, at least in general driving.

Bob - Sorry, but I had my response pretty well ready to post when you posted, and forgot to mention that you recommended the same thing that Steve and Tire Rack did - more/some toe-in.  Thanks!

And, a fun fact: As it turns out, with 33" tires my CAD program says that each .01 degree of toe-in brings the edge of the tire in .005".  And since you are doing that with both tires each .01 degrees gets you .01" of toe-in.

I "see" what you are talking about with track bar vs drag link length, suspension "cycling", etc.  It is an adjustable track bar, but where I have it puts the front and rear tires in alignment with each other with the truck on the ground.  That took a lot of adjustment to do, but it seems to be what you are supposed to do.

However, if the toe-in adjustment doesn't do the trick then I could try adjusting the track bar.

On the sway bar, I'm with you that it won't make much difference in steering.  Taking it off didn't, and there's essentially no sway at the present so I'm not seeing the need.

Gary Lewis wrote

I "see" what you are talking about with track bar vs drag link length, suspension "cycling", etc.  It is an adjustable track bar, but where I have it puts the front and rear tires in alignment with each other with the truck on the ground.  That took a lot of adjustment to do, but it seems to be what you are supposed to do....

I'm not suggesting you "just" change the length of the track bar.  If you made it the same length as the drag link your front axle would stick a couple feet out the right side of the truck!  I'm just saying that it's not clear to me what bump steer you might expect, or if there is anything you might do to minimize it.  Like I said in my first post, typically adding a drop pitman arm to make the drag link closer to horizontal is a way to reduce bump steer.  But I don't know if that would be a good idea here or not.

Tell you what - if the toe-in adjustment doesn't dial it in close enough for me, or if the wandering is gone and I still have bump-steer, then I'll do some measuring and draw up the suspension.  Then I can do what Bill suggested and see what happens when it cycles.  (I assume there's a way in TurboCAD to connect parts and have them move in concert.)

I hope I didn't misspeak about your SAS RSK Gary.

The wider tires aren't helping any here, and the 'optimum' seems crazy.
.06* +/- .25* ???

Is .31* to -.21* !!!

So the tolerance is more than 4X the actual setting?

No Jim, you were spot-on about the front end.

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.

But, looking at the spec's on the computer that the alignment shop uses, they show +/- .13 degrees for a total of .26 degrees.  

.13 is more than still twice .06..  

And I can't imagine anyone specifying thousandths of a degree.
It's a truck, not a cyclotron.

I agree on the thousandths of a degree.  I watched Steve play with the adjustments and it took very little to make a difference.  So, maybe they really did mean it?  

Gary Lewis wrote

Tell you what - if the toe-in adjustment doesn't dial it in close enough for me, or if the wandering is gone and I still have bump-steer, then I'll do some measuring and draw up the suspension.  Then I can do what Bill suggested and see what happens when it cycles.  (I assume there's a way in TurboCAD to connect parts and have them move in concert.)

Gary three things on track bars, first, if it doesn't make a handling difference, why do race cars have adjustable ones? Second, when I was helping and crewing an MG Midget for a friend, it had quarter elliptic rear springs, a half length spring that was bolted to the body by what would be the center of a semi elliptic spring and the eye attached to the bottom side of the rear axle, the top had a link that ran to the body above the spring so the axle moved straight up and down. It used a track bar to keep the axle aligned side to side. We had a suspension guy (circle track type) come and look at the suspension one evening. He had the driver, suited up and in the seat with the car supported on jack stands, rear ones under the axle. He had us make an adjustable length track bar and then set it exactly parallel to the axle at static load. Third, 1955-56 Packards had trailing arm torsion bar rear suspension (bars went all the way to the front) and had a Watts linkage rear track bar system so there was no side shift going up or down.

On your steering linkage, from what I remember of the pictures, both tie rods angle down, right side from the pitman arm, left side from the center of the truck. Darth's do also, but Darth being a 2WD means he has twin I Beams that cross pivot so are longer than the tie rods effective length (center to knuckle) so the effect pretty well cancels. On BB since the knuckles are a fixed distance apart, any vertical motion will change from toe in to toe out very easily, further at the present track bar position as the axle comes up toward the frame, it shifts slightly to the right meaning the left front wheel will toe out more than the right one.

I know that a 4WD front end is a compromise in alignment unless it is full time. It has to be able to drive well in both conditions and one of the issues is toe in, under power it will toe in more then it will just rolling in 2WD, hubs unlocked, locked is more drag and ,more tendency to toe out, under power, more tendency to toe in.

Tires, the desired size tire on the proper rim places the center of the contact patch at the center of the king pin axis (even if you don't have true king pins like Darth does). If the contact patch is not centered then you get torque steer under power (ask how I know this) with a live axle you shouldn't get as much as either independent or twin traction beams as a lot of it is caused by the CV joints at the inner end trying to straighten out under power, however if the contact patch is outboard of the king pin axis, and one tire has less or no traction, you better have a good grip on the steering wheel as the side with better traction will want to turn you the opposite way.

Remember Bill that this truck has RSK, so any bump is going to tuck the axle back under the steering box.

I'm not sure where this places the axle in relation to the pitman arm joint but I am sure Ackerman is changing quite a bit as suspension cycles.

85lebaront2 wrote

....  On your steering linkage, from what I remember of the pictures, both tie rods angle down, right side from the pitman arm, left side from the center of the truck. Darth's do also, but Darth being a 2WD means he has twin I Beams that cross pivot so are longer than the tie rods effective length (center to knuckle) so the effect pretty well cancels. On BB since the knuckles are a fixed distance apart, any vertical motion will change from toe in to toe out very easily, further at the present track bar position as the axle comes up toward the frame, it shifts slightly to the right meaning the left front wheel will toe out more than the right one....

I think you're remembering the pictures wrong, or maybe remembering old pictures from when Big Blue had a TTB.  I'm pretty sure Gary has essentially a stock F-350 linkage now (albeit lifted).  So I'm pretty sure he has a single tie rod going straight from one knuckle to the other.  There would be no effect on steering geometry from suspension motion due to the tie rod.

Then he has a single drag link angling down across the truck from the pitman arm pretty high on the driver's side down to either the passenger side knuckle or else it might attach to the tie rod.  That's what could cause bump steer, especially since the track bar is such a different length.  But it shouldn't cause wandering.

Now if I'm wrong and Gary is still running F-250 steering linkage with the F-350 axle, then yeah, fix that!