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     Okay, after searching the internet for a few weeks on topics for correctly setting camber and caster on a solid axle front end I have come to a conclusion: Very few people know this answer and of those few that do, very few want to share it.  

 

      I know the general consensus is to take your vehicle to an alignment shop and kick it in the lobby reading old Car and Driver magazines while they run your car or truck through the paces. In the end, they hand you a paper with + this, - that, drop some terminology on you, you shake your head and agree, plop 60 bucks on the counter and drive away. Well that's fine and dandy on the old Buick Le Sabre, but guys like us with lift kits, oversized wheels and tires and custom front end work, well...not so much. I have yet to find a shop that will entertain the idea of even aligning my truck.

 

   I can’t believe that there is no way a DIY can do this at home. Yes it may not be aligned within +/- .0001, but neither is yours after the first pothole you hit leaving the shop. There had to be a way they did alignments before the construction of the modern alignment machine. I believe with some time and effort, a DIY guy can get pretty close if not close enough to get within spec.

 

  My questions here are to cover the solid front axle of my '06 Dodge Ram 3500, and I assume this will carry over, in principle, to a lot of other solid axle trucks.

 

  To my understanding there are 3 basic adjustments to consider. Camber, caster and toe. Now this leads me to my first set of questions before we even go to these 3 topics. Axle placement under the vehicle. This seems to be a grey area in knowledge on the web so here goes.

 

  1. I have an adjustable track bar that will allow me to adjust my axle left and right in the vehicle. What is the proper way to measure the placement of the front axle so you know it is truly centered under your truck? I have done some simple string lines and measurements and feel mine is good. I just want to get the proper information out in the open so I can verify my work and others can use it if needed.

 

  2. How do you measure your front axle and know it is square with and in the truck? You know, to verify the left tire isn't further forward in the vehicle that the right tire. Now, I have read this is how you would align a solid front axle vehicle to control it veering right or left while driving. Is that true? If so I would still assume you would want to have a zero starting point for making adjustments. I also assume this measurement is probably based off of the rear axle's location in the truck. Well, since I have never had any rear axle damage or any changes done, I assume it is straight and located within spec. Or should we back this whole conversation up and start by confirming the rear axle location and making all other measurements from there??

 

  Well if we make it through this first part I guess we can move onto my camber/caster questions:

 

  Camber. I have a basic understanding of how camber and caster is adjusted and how it affects the vehicle so no need to cover that, but feel free to if you want. I also know that with my truck the upper and lower ball joints are fixed and centered. This would lead me to believe that camber on my solid axle front end is at the mercy of the axle caster settings. Without the use of some offset ball joints of course.

 

   I recently have upgraded my ball joints to the Carli Suspension ones. Very nice and very well built. During this install is when I noticed my truck had a serious amount of negative caster, which possibly was one of the underlying issues of the poor handling. Well possibly partly lol. Most of the handling issues were poor steering components. That topic is covered by one of the other threads on this forum.

 

  Now on to caster. From where on the front axle do you take the measurement for caster? Do you really have to have a special tool or is there more of a DIY approach that can be done? I can’t believe you must have NASA grade tools with Sheldon Cooper knowledge. It’s only a few degrees. If this is possible to do at home what are some others pointers to consider? Should both sides match or is this something that has a "room for error" type thing?

 

  Like I mentioned before my truck has a long arm 4 link front end with adjustable links. I can move my front axle front, back, left, right, twisted front, rolled back, in, out you name it, so making caster adjustments should be very easy. Making proper adjustments...well that's why I'm here.

 

  Toe adjustment. While this seems to be the simplest one, I believe that it should be last. I figure with the way the knuckle works, if you made any toe adjustments before properly setting caster adjustments, it would be off?? I assume your castor must be set before taking anything else into consideration.

 

  Considerations...What are considerations to any of these adjustments and measurements when dealing with oversized wheels, tires and lift kits? To me, I can see an issue with the offset of my wheels and the intersection of the caster angle through the ball joints in correlation to the ground surface and the contact spot of the center of my wheel and tire. I see that instead of my wheel and tire rotating on this centerline I am instead actually arcing around it if you will (if that makes sense). Maybe these things only matter at high speeds, maybe not. I can see the offset being harder on ball joints but that's why I choose Carli.

 

  I understand with a lift kit people run into problems because the need to get your pinion angle on the front axle correct to reduce vibrations. Well I have installed a free spin kit with lockouts so pinion angle is not a priority. I am willing to deal with a front end vibration the 2 days out of the year I need 4 wheel drive in exchange for 363 days of correct steering geometry. For others without the free spin kit I can see your need to address this issue differently.

 

  I don't know, maybe this is all secret squirrel information, and nobody will share it. I don't deem it rocket science, but I believe it should be done properly. If an alignment shop is the only accepted way to do it, so be it. I just can’t believe that's the case, though. Any input on any of this subject would be appreciated. As always, I know Moses will break it down tech style, and that's fine by me.  Attached are a couple pictures of my front end with corrected 4 link angles and new poly joints.

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All good points, Megatron, each deserves an explanation, so here we go...I'll begin by sharing that I ran a four-wheel alignment rack at a GMC truck dealership in the mid-'80s, the era of both beam front axle 4x4s and IFS 2WD and 4WD front ends.  For fifteen years prior to that, I had been doing alignment with far less equipment than that new Hunter four-wheel, electronic light beam rack.  Fifteen years after the dealership stint, I taught wheel alignment at the adult vocational training level and merged my varied equipment experiences, which reflect in what I'm now sharing.

It's great to use precision four-wheel alignment equipment.  However, "computer" alignment equipment is also limited in many ways.  For example, you describe aftermarket wheels, suspension and tires, and you're right, of the three (assuming the suspension kit is as adjustable as yours), the wheel offset is the most critical modification.  Because your truck falls outside the OEM guidelines built into the software for modern alignment equipment, many shops will avoid doing your truck's alignment.
 
Reasons for refusal include "liability", "unpredictable results" and "possibility of abnormal tire wear"—regardless of the alignment procedure.  In many cases, the shop simply doesn't know what they can do to address or compensate for your modifications...After all, this is the era of plug-and-play.  Follow the flow charts or stare at the computer screen or scanner.  Wait long enough, and maybe an answer will materialize...That's not going to happen here!
 
For now, let's suspend judgment about why your truck and millions of other 4x4s are in this predicament.  You've installed all of this hardware, and it's time to make the vehicle track as safely as possible—and for the tires to last.
 
As for front axle lateral alignment, your adjustable track bar is a real asset.  Alignment does reference from the rear axle, and for good reason.  The term "thrust" is just what it sounds like: The rear axle on a RWD vehicle is the traction point, pushing the frame and the entire vehicle forward from the rear.  Unless you're driving backward, your rear-drive truck requires the front axle to align squarely under thrust.  (Thus the term "thrust alignment"!)  The axles must be square, in any case.
 
To illustrate, draw a line forward and perpendicular to the centerline of the rear axle.  This follows the driveline in approximate terms—unless the driveline is offset like with a side-drive transfer case.  This line of force, aimed forward and perpendicular to the rear axle, becomes the reference point for the front axle's position.  The front axle ends up parallel to the rear axle, which is simple to visualize on beam axle trucks like our Ram 3500 models.  The front axle must also align sideways or laterally, the reason for your adjustable track bar.
 
Whether the frame is perfectly square or not, if the front axle is parallel to the rear axle (plane view from the top), and if the axles center laterally with each other, you can align the truck's front end.  The frame should be square, though, because an out-of-square frame would place the springs, suspension arms and steering linkage at odd angles with the axles.
 
So, let's start with a square frame, no collision damage, and a rear axle that sets squarely in the truck.  It's much easier with our leaf sprung, beam rear axle:  The centering points for the rear axle are simply the leaf spring center bolts and the axle's spring perch holes—plus any spacer block alignment holes or pins.
 
Rear axle in place, you can use the string-in-diamond method for setting the beam front axle's position for both parallel to the rear axle and laterally on center.  I used the string method for two illustrated how-to articles at the magazine: my Jeep XJ Cherokee 6-inch long arm installation at the "Jeep XJ Cherokee & MJ Comanche 4WD Workshop" (see the left panel menu) and also the Jeep TJ Wrangler Rubicon Full-Traction Ultimate 4-inch lift.  The XJ Cherokee is similar to our Dodge Ram trucks with link-and-coil front suspension and leaf springs at the rear.  Both Jeep vehicles have beam axles front and rear.
 
Critical to a string-in-diamond beam axle alignment is finding precise reference points at each of the axles.  You must have a reference point at each side of the front axle that is truly equal distance from the axle's centerline.  The rear axle on our trucks is simple:  Use the leaf spring center bolts as the rear reference points.  On a Jeep TJ or JK Wrangler, there are matching suspension points that are equidistant from the rear axle's centerline.
 
The front axle should align with equal string lengths to the rear axle, measured in cross or "diamond".  This means measuring from the front axle's left side reference point to the right rear spring center bolt, then from the front axle's right side reference point to the rear axle left side spring center bolt.
 
This measurement must be very accurate.  Even 1/16"-1/8" variance can make a difference.  If there are obstacles under the chassis that prevent an accurate measurement, you may need to relocate your reference points or even make "extensions" from the reference points to below the obstacles...For these measurements, you can have the axles suspended to full drop, which may help the string lines clear the transfer case skid plate, the exhaust or any other objects in the way.
 
Be creative.  It's crucial that your four reference points reflect equal distances from the center of each beam axle outward to each axle's reference points.  Strings then measure in cross between the front and rear axle reference points.
 
Again, the end game here is to have the axles parallel and tracking in line with each other.  When the front axle is offset laterally, one way or the other, we call this "dog tracking".
 
Note: Don't be confused if one axle's track width is actually slightly wider than the other axle with the wheels in place.  Some trucks (G.M. beam axle 4x4s come to mind) were designed this way, typically with the front axle slightly wider than the rear.  I won't digress into "why" this was the design, simply know that if your reference points match side to side on each axle, and if you run the string lines in cross to matching points at the opposite axle, you will determine both the square and lateral alignment of the two axles.
 
Checking for square with two strings-in-cross is a simple function of geometry.  If anyone is having difficulty understanding the principle, draw a perfect square on a piece of paper; now draw an "X" from opposite corners, intersecting at the middle.  Measure the length of each "X" line.  It will be equal.  If you now use a rectangle instead of a square, the results will also be two equal length, intersecting lines.  Play with this, and then transfer the "X" lines to your truck's chassis:  On your long wheelbase Dodge Ram 3500 truck, the beam axles represent the short ends of a rectangle.
 
The most elaborate "4-wheel" alignment machine will not produce any more accurate results than doing a string line test properly.  Once you get the axles square, you can concentrate on a front wheel alignment.  This, as you say, is not rocket science, and it's even easier with a beam front axle.
 
Camber, in particular, is factory pre-set on a beam axle.  Camber measurement indicates the degree to which the axle beams, steering knuckles and ball joints are in alignment.  As you mention, you can make camber corrections with off-set ball joints, or eccentric ball-joint seats, and a source for such parts is Specialty Products Company.
 
Caution: I am against "bending" beam axles to correct slight camber issues unless a racing, weld-on truss is part of the straightening process.  (Be aware, too, that welding on a truss is a good way to warp an axle and alter camber!)  Consider the axle tube and center section materials plus the original stress that caused the axle to bend.  There are metallurgical changes that take place with cold or hot bending.  If you need to correct for a slightly bent or out-of-spec axle beam, use offset ball-joints or eccentric ball-joint seats.  Make sure the bend did not stress-fracture the axle pieces.  Toss out the axle housing if in doubt—you can transfer internal pieces and add-on goodies to a new housing.  (See the magazine's many axle rebuilding articles and the HD videos on axle setup.)
 
Be aware that beam front axles come from the factory with +/- camber often slightly beyond the factory recommended camber degree range.  I have seen this on Dana Jeep front axles, typically at the short beam side with more factory welding. An extra 1/8 to 1/4-degree camber at one side is not earthshattering and likely was acceptable during OEM axle assembly and installation.  This will not impair vehicle handling and has negligible effect on tire wear if you rotate your tires on time.  If you are adjusting caster and camber with offset ball-joints or eccentric ball-joint seats, bring both the caster and camber within their recommended degree ranges.
 
To answer your questions about "do-it-yourself" alignment, go no further than these three features that I've done at the magazine.  They each get brisk traffic, addressing alignment goals with inexpensive solutions for doing your own alignment work.
 
First is the ‘DIY’ feature on a beam front axle wheel alignment.  This is a useful article for understanding the principles of front wheel alignment as well as a 'how-to' on using an affordable SPC Off-Road Fastrax 91025 gauge kit designed for tires to 44" diameter.  Click here to see this DIY how-to and equipment article.

 

For those on a shoestring budget, a single gauge kit will do.  You can even improvise on the need for turn plates.  SPC suggests using plastic sheeting beneath the front tires for a slip surface.  On a beam axle, you can unload the weight slightly with the use of two floor jacks, raising the weighted axle evenly and just enough to take the heavy load off the front wheels and tires.  This provides easier wheel turning.

 

There is also a photo closer to home, my Dodge Ram 3500 4x4 alignment after installing the Mopar lift kit.  Here, I purchased inexpensive front turn plates ($100 for the pair!) from Gil Smith Racing at New York.  Gil is a personable family guy, and these plates do the job despite the massive front end weight of the Cummins engine, 9.25" beam axle and 500 pounds of Warn bumper with M12000 winch and stainless wire. 

 

For the Dodge Ram alignment, I added a second Fastrax 91025 alignment gauge kit from SPC to make toe setting easier and quicker.  This way, you can use the winged braces and separate gauges at each side of the truck during the alignment procedure.  This eliminates the need to swap a single gauge set from one side to the other. 

 

Last, but surely not least, is the HD video walk-through of alignment on a Jeep TJ Wrangler Rubicon.  You'll like this for both a visual orientation and added quips about the process.  In this HD video, I do use the double alignment gauge sets from SPC and the Gil Smith turn plates.  You’ll see how this speeds up the process.

Some additional pointers on doing your own alignment at this level:  1) make sure the floor is flat in both directions or compensate when taking the measurements with the bubble gauges, 2) make sure the turn plates are thin (like the Gil Smith type) or if you spring for more commercial type turn plates (available from several sources, do a Google search under "wheel alignment turn plates"), make sure you raise the rear of the truck to compensate for the turn plate height at the front.  Even with a 140.5" or longer wheelbase, a sloping or leaning truck will throw off your camber and caster readings with the SPC 91025 bubble gauges...If you want to add a touch of professionalism, purchase a pair of rear slip plates from Gil Smith Racing that will enhance the work and raise the truck's back end to match the front turn plates.

 

As you mention, always save the toe-in setting for last.  Camber and caster angle must be right, with the vehicle setting at static (curb) height on the ground, before setting toe.  I use factory toe-in and caster angle settings, and the Dodge Ram handles very well.  And, yes, caster is important, this and steering axis inclination (SAI) are what return the front wheels to center after coming out of a corner.
 
The surest sign of too little caster angle is a vehicle that requires turning the steering wheel back to center after a turn.  I'm at 4-degrees positive caster on the Dodge Ram 3500, closer to 7-degees positive on the XJ Cherokee.  More can sometimes be better for off-pavement turning radius; however, factory specs are the best for normal tire wear and handling in general.
 
I mentioned another specification that is of concern during alignment:  steering axis inclination (SAI).  We can go into this if you want, but the important thing to note for DIY alignment purposes is that strange caster and camber angle readings over the full turning arcs (illustrated in the XJ Cherokee alignment how-to article and shown in the TJ Wrangler HD video coverage) are an indication of a bent steering knuckle on a later beam axle 4x4 or a bent spindle on 2WD and vintage 4WD vehicles.
 
On alignment equipment that will identify SAI error, if all measurements are correct and SAI is off, we inspect the steering knuckle, spindle or unit bearing hub for damage.  Make sure any strange readings are not from bad steering knuckle ball joints or worn wheel/hub bearings!  Better yet, inspect for ball joint, wheel bearing and unit hub bearing wear before attempting the alignment.  Check steering linkage for loose joints, too.
 
This is ground school, we can go from here.  As a light- and medium-duty truck fleet mechanic in the late 'sixties, I began aligning my own beam axle Jeep CJ3A and vintage '55 Ford F100 at home.  On these vehicles, toe-in could be set with nothing more than a tape measure.  If you do wheel alignment with turn plates, the steering linkage and suspension will be unloaded, and the measurements will be that much more accurate.  Add rear wheel slip plates and Fastrax gauges, and you can emulate a "pro" alignment!
 
Even on the vintage 2WD and 4WD fleet trucks with beam axles, I did quick, rough-in beam axle wheel alignments with nothing more than a tape measure or a portable, adjustable "toe bar".  Floor jacks were placed evenly under the axle at each side.  I would lift the axle beam just enough to "unload" the wheels and tires.  Before setting toe, I made sure the wheel bearings and kingpin bushings or bearings were in good shape and adjusted properly.

 

Tape measure alignments on the trail are often necessary when someone bows a tie-rod on a tall rock or snaps a tie-rod in half.  A Ready Welder tie-rod repair at Moab's Rose Garden is just one place where your tape measure alignment skills would be popular.  This can get a vehicle home from the trail and tracking down the road safely to a wheel alignment shop.  When using just a tape measure for toe-set, make sure you follow the tread pattern closely at the front and rear midline of the tires.
 

When using turn plates to unload and center up the steering linkage and suspension, it helps to bounce the front end.  Push down on the front bumper a few times—the bumper is conveniently located at waist height on your Mega Cab!
 
If necessary, use a pair of floor jacks under the beam front axle to take weight off the wheels and tires, then lightly rock the steering wheel at its center position before setting the front tires and steering wheel to straight ahead.  This will unload the steering linkage for more accurate alignment settings.
 
When using a tape measure only (not the Fastrax 91025's wing arms), always measure matching tread points.  Measure as close to the midline (3 and 9 o'clock) of the tires as possible.   Avoiding obstacles is sometimes difficult, but midline of the tires is preferred.  Always set toe-in, followed by centering up the steering wheel.  You center the steering wheel by adjusting the steering linkage sleeves—never by removing the steering wheel and repositioning it!
 
Caution:  The steering wheel spokes are factory set to align with the center or “high” point of the steering gear in the straight ahead steering position. Bring the front wheels into alignment with the centered steering gear and steering wheel—not the other way around!  If the steering wheel has been repositioned from factory, find the precise center point of the steering gear.  Position the steering wheel there before aligning the front wheels to straight ahead.  This also applies when making fine steering wheel position changes after an alignment:  Adjust the steering linkage sleeves, do not reposition the steering wheel!  Always check toe-in again when you center the steering wheel.
 
To illustrate how well you can do a 4-wheel alignment with strings, a tape measure, a common spirit level and a protractor, I installed the Full-Traction Ultimate lift kit on the Jeep TJ Wrangler Rubicon in just that way!  The job began with the vehicle on my hoist and as level/parallel to the ground as possible.
 
I placed a pair of adjustable tripod stands beneath each axle and raised the vehicle straight up, just enough to install the lift kit.  The axles remained on the stands with cables and other chassis attachments still in place.
 
After installing the kit, including a bevy of adjustable link arms and a unique rear tri-mount suspension system, I used the string method to square the axles.  The rear axle location, fortunately, was fixed by the kit’s design, so this became the reference for making everything square with the frame.  The approach was similar to the rear leaf springs and center bolts on our Dodge Ram 3500 trucks.  In our case, the rear springs and axle spring perches locate the rear axle squarely at the frame.
 
I set the caster with a quality bubble level and a 180-degree, indexed protractor.  I set toe-in with vehicle weight on the axles and tripod stands, using a tape measure fore and aft (as close to 3 and 9 o'clock as practical) at the front tire midlines, keeping the tape as level and parallel to the floor as possible.  In my view, this was all just a preliminary, rough adjustment.
 
The next stop was a friend's shop with a $40K alignment rack capable of 4-wheel "thrust" alignment.  On the alignment rack, to everyone's surprise, the entire suspension system took only one-half turn of one threaded link arm tube to be fully square!  Caster was on, camber (non-adjustable on a solid beam axle) was okay, toe-in and centering of the steering wheel were just routine, slight adjustments. 
 
Caster angle was within spec and did, as you describe, provide an acceptable angle for the front/pinion U-joint flange.  With a double-Cardan (CV) joint at the transfer case, there is some leeway on this front axle pinion joint angle, and the compromise is between caster angle and U-joint angle.  Like you comment, caster usually wins if you want the vehicle to steer correctly!
 
For modified trucks with suspension lifts and oversized wheels and tires, there are two very important considerations for handling.  First, the aftermarket wheels' offset and the tire diameter must provide the right intersect point with the ground.  This is the “scrub radius”. 
 
Visualize the front wheels pointed straight ahead.  Draw a line through the ball-joint stud centerlines and observe where that line intersects the tire tread at the ground.  This point must be similar to the OEM wheel/tire intersection point, or you will swing the tire on an odd arc during turns, resulting in strange handling and premature tire wear.  Scrub radius impacts tire wear as well as handling.
 
Secondly, consider the arc of radius and caster angle changes as the front suspension (link arms in your case) rise and set.  Arc of radius is why we do long-arm kits for dramatic lift.  When we increase suspension travel, short arms exaggerate the caster angle changes as the suspension extends and compresses.
 
Long link arms are the solution for increased suspension travel.  Longer arms will create less caster angle change over the suspension and axle’s arc of travel—or radius.  Simply put, you can set the caster at static/curb weighted chassis height, and the caster angle does not vary excessively as the link arms move up and down with the axle.
 
When buying an aftermarket suspension lift kit or bigger/wider wheels and tires, consider these issues.  In looking at your Mega Cab components, I really like the stamina and quality of the aftermarket joints, link arms and drop brackets!  What you want at the end of the day is suspension that behaves as well as or better than OEM engineering—yet with the lift and tires you desire.  Going beyond “looks”, the goal is to understand the demands and dynamics of vehicle suspension and handling.  Doing your own wheel alignment is a good start.
 
As for the rear axle, the usual concern is pinion and driveline angles for U-joint survival.  Within reason, you can rotate the axle housing for pinion angle change without affecting vehicle handling, as the rear drive axle’s shafts are not sensitive to caster.  (If we were talking about a front wheel drive car or an IRS/AWD car, there would likely be provision for adjusting rear wheel caster, camber and even toe-set.)  For our trucks, tall lift blocks at the rear leaf springs can create some issues, mainly traction and spring windup related.
 
So, you might skip the visit to the local 4-wheel alignment shop and the brief Car and Driver  read—likely just long enough for the tech to discover that specifications for your lifted and modified '06 Dodge Ram 4x4 Mega Cab are nowhere to be found in the alignment machine's software program.  As an option, consider the SPC Off-Road 91025 alignment equipment...Two kits work even better than one!
 
Used properly, this accurate, portable SPC setup can help you dial your front end alignment for both safety and good tire life.  Bubble caster and camber gauges were an automotive industry standard for at least sixty years prior to light beam, infrared, RF and laser alignment equipment. 

 

I entered the service and repair industry when we were still called "mechanics", and breaker point ignitions were the norm.  Smaller shops used floating caster/camber bubble gauges that fit magnetically to the end of front wheel hubs!  Professionally, I've spun wrenches all the way into the contemporary electronic fuel-and-spark management "technician" era.  Electronic, beam four-wheel alignment equipment has been in vogue for more than three decades now...I find it advantageous to have walked in both worlds.
 
Beyond alignment, make sure that the wheel offset and tire diameter add up to a safe and tolerable "scrub radius”.  As an alternative to Car and Driver, sift through this Wiki info about scrub radius and SAI.  When you widen the wheel rims, you can only go inward so far.  (Rotors, calipers and hubs limit the inward wheel position.)  For that reason, wide rims almost always offset to the "negative" direction or outward.  If there are wheel backspacing choices, match up the wheel width, backspacing and tire diameter wisely!  The concern here is the scrub radius.
 
We lift our vehicles and mount oversize wheels and tires for a variety of reasons.  In the end, we get to make the handling and safety corrections that these modifications require.  Routine tire rotation is always essential, even more so when scrub radius and arc of radius get compromised.  Once you dial the front end alignment to the best point possible, watch for ball-joint wear, wheel bearing or hub bearing wear and any tire issues.  This can sometimes be the price for a lift and oversized tires.  We can, however, reduce, minimize or even eliminate that risk and expense!
 
Moses

 

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First off, Excellent write up, nice to see some thoughtful and relevent information out there! I am curious what the SAI and included angles should be on the Dodge Rams with a 9.25 AAM front axle? Also, when doing adjustments how do they interrelate? What I mean is by rotating the axle with caster will the camber or toe be effected? Would adjusting toe effect camber? Etc.

 

Moses Ludel, on 27 Jul 2013 - 3:16 PM, said:

I mentioned another specification that is of concern during alignment:  steering axis inclination (SAI).  We can go into this if you want, but the important thing to note for DIY alignment purposes is that strange caster and camber angle readings over the full turning arcs (illustrated in the XJ Cherokee alignment how-to article and shown in the TJ Wrangler HD video coverage) are an indication of a bent steering knuckle on a later beam axle 4x4 or a bent spindle on 2WD and vintage 4WD vehicles.

 

 
On alignment equipment that will identify SAI error, if all measurements are correct and SAI is off, we inspect the steering knuckle, spindle or unit bearing hub for damage.  Make sure any strange readings are not from bad steering knuckle ball joints or worn wheel/hub bearings!  Better yet, inspect for ball joint, wheel bearing and unit hub bearing wear before attempting the alignment.  Check steering linkage for loose joints, too.
 

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Thanks, Driven!  Back to SAI (steering axis inclination), this is factory predetermined on a beam axle like our 9.25" AAM.  You can only adjust the caster and camber with the use of aftermarket offset ball-joint studs from a source like Specialty Products.  The process begins on the alignment rack or with the kind of DIY equipment that I discussed (also from Specialty Products). 

You determine the error in caster, camber or both, then select the right offset joint to compensate for caster, camber or both errors.  This is based upon your gauge findings.  The presumption is that once caster, camber and toe-in are each adjusted correctly, the SAI will naturally be correct—unless the steering knuckle or spindle (on an earlier full-floating 4x4 front axle or an IFS 2WD) is bent

Alignment, because of the factory error +/- factors, is sometimes a compromise.  In some cases there is a cross caster error between each end of the beam axle.  With stock (centered stud) ball-joints, you attempt to adjust the caster at one side of the axle, and the other side goes out of spec.  A compromise is then necessary to find a sensible and safe median. 

These beam axles are seldom "on spec".  Camber, in particular on solid/beam Dana front axles is almost always slightly out of spec on the heavily welded side of the housing.  Some think this is from damage or a zealous transport tie-down situation.  (I have seen frames bent from incorrect tie-down approaches.)  In my experience, with brand new Jeep 4x4 models, the beam axle often has "factory" camber or cross-caster error, just slightly out of spec but still tolerable, not enough to prematurely wear tires if rotated.

To show how this works from an OE standpoint, here are the 2005 Ram 3500 4x4 (beam 9.25" front axle) specs for alignment.  Note that the caster is adjustable with link arms.  Camber is "non-adjustable", and the toe-in is, of course, readily adjustable.  The OEM does not consider installing offset ball-joints, though I'm sure that body shops have brought many beam front axles back into camber or caster alignment through this method.  (The alternative is to install and fit a new bare front axle housing, and most shops do not want to go that expense and work.)  Some corrections for "pull" might get this kind of attention under warranty or even the simpler offset ball-joints.  Be sure to distinguish cross-caster error pull from a tire radial pull!  It is common practice to first swap tires left to right if a front end on a beam axle 4x4 pulls to one side.

Note: A friend who purchased his brand new 2014 Ram 2500 4x4 immediately had the cross-caster corrected (with a Specialty Products ball-joint) because he wants his truck to steer straight without input on a long stretch of off-camber highway!  (That's very particular, most of us live with left or right tension pull on cambered roadways, and that pull varies with the road angle or camber.) 

According to the OEM, here is all the alignment info considered of value to the tech or dealership:

 2005 Dodge Ram 3500 4WD Front End Alignment.pdf

With SAI, the reading is basically an alignment shop or collision repair topic.  The search for a bent spindle or steering knuckle is assumed to end once caster, camber and toe are corrected and the SAI comes within spec...SAI does have an impact on handling and tire wear.

I have used the Specialty Products alignment equipment and inexpensive Gil Smith turn plates to do very accurate alignment work on both our '99 XJ Cherokee and the Ram 3500 4x4.  On beam axle models, I even simulate a four-wheel alignment with a simple tool:  String measurement in diamond or cross between matching front and rear axle points.  This can catch an out of square axle or frame condition (essentially a check for thrust alignment) and even dog-tracking.  The precision geometric form, measured with equal length strings, is simply triangles!

On a Jeep TJ Wrangler long-arm, fully adjustable link suspension with a tri-link rear (Full-Traction Suspension's Ultimate kit), I have adjusted the front to rear axle and frame alignment with string measurements in diamond to such a degree of accuracy that a four-wheel electronic alignment machine ruled out the need for further adjustment...With practice, you can do this, too!

Moses

 

2005 Dodge Ram 3500 4WD Front End Alignment.pdf

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With SAI, the reading is basically an alignment shop or collision repair topic.  The search for a bent spindle or steering knuckle is assumed to end once caster, camber and toe are corrected and the SAI comes within spec...SAI does have an impact on handling and tire wear.

The reason I am interested in this is because my truck was recently damaged in a accident. The alignment shows that camber is out of spec by -1 on both sides and toe is set out 1 degree between both wheels. The cross camber and cross caster are within spec, giving a SAI of 15.25/15.35. No required SAI angle is given. The alignment shop thinks the housing is bent. It seems odd to me that the cross specs would be so close on a bent housing, so I am trying to narrow down exactly what, if any, damage there is.

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Driven...Cross caster and cross camber are simply cancelling each other, which is not to say they are "normal".  For accident damage to cause camber to change -1 degree would be something like the truck being dropped from some height onto the front wheels/tires.  The "bend" would be a bow upward.

If the truck has higher mileage, I would try to rule out worn or damaged steering knuckle ball-joints before concluding that the axle housing is bent.  How many miles are on this vehicle?  The Ram's beam axles, especially with the Cummins engine weight, are noted for knocking out the OE knuckle ball joints.  Sagging ball joints would lean toward negative camber.

I'm a stickler for angles.  I would want to pull the axle shafts and remove the knuckles, then run centered bars through the axle housing's ball-joint bores and measure the bar spread (top width compared to bottom width) to isolate whether the housing itself is bowed.  The use of offset ball-joints could alleviate camber discrepancy if you'd prefer that route.  Keep in mind that these axles from the factory are never precise camber, and sometimes they run out of the OE limits as well.  If tire wear is not an issue and the owner does not complain of pull or wander, these axles often lead a long, unnoticed life.

That said, you do want to know if there is physical damage to the axle housing that needs attention.  Otherwise, leaks at the tube-to-differential can occur, axle shafts can run off-center (extreme case of bowing) and cracks or stress weakening is hazardous.  Generally, I'm against "straightening" a housing by cold bending.  Stretched and straightened metal likes to return to the bent shape (called "memory") and often will do so after straightening.

If the work were not insurance covered and if you were spending your own money on this repair, another approach beyond ball-joint work would be installation of a support truss.  These aftermarket devices are typically for severe off-road use on beam axles.  They traverse from the steering knuckle flanges across the axle's center section.  Some are weld-on, others are plates and rods with adjustable threads.  If the curved axle tubes were brought into alignment then trussed in this manner, they would likely stay put.  Here are some examples, mostly used for high performance racing or hardcore 'wheeling with grossly oversized tires:  https://www.google.com/search?q=axle+housing+trusses&biw=2560&bih=1345&tbm=isch&imgil=M-tBinAYARcCbM%253A%253BOvBNTjy-MuN44M%253Bhttp%25253A%25252F%25252Fwww.jeepinoutfitters.com%25252Fproducts%25252Ftnt-customs-front-axle-housing-truss-d30&source=iu&pf=m&fir=M-tBinAYARcCbM%253A%252COvBNTjy-MuN44M%252C_&usg=__jeuUIdizv7411iJ5MctnHx6T9xw%3D&ved=0CCYQyjdqFQoTCMiciNn168gCFQk7JgodUx0Lbg&ei=zUk0VoiCF4n2mAHTuqzwBg#imgrc=M-tBinAYARcCbM%3A&usg=__jeuUIdizv7411iJ5MctnHx6T9xw%3D. 

In viewing these images, the takeaway for me is the vulnerability of beam axles under extreme stresses.  Note that most of these axles have the tubes welded to the center housing.  This not only makes the axle housing rigid, it also eliminates the leak issues common to these axles when either flexed too much in service or welded.

Moses

 

Edited by Moses Ludel
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