Alignment/Measurement Question - Caster of Front Wheels

I recently replaced upper ball joints on a '96 Dodge 3500 (1-ton) van. This vehicle uses pressed-in ball joints, and I replaced them with a standard C-frame tool. After a few months, one of the ball joints
backed itself out (this is a poor design, IMO). I pressed it back in, and tack-welded it in a few spots. So far, it's holding just fine.
In order to do the weld, I removed the upper A-frame. Of course, I didn't think to mark it's position (uses no shims, just slotted bolt holes to adjust caster/camber) until I'd already loosened the bolts and let things shift.
I'd like to get the truck properly in alignment. If that's not possible, at least driveably close until I buy new tires and have a shop fine-tune it.
I think I can measure camber with a plumb bob, and toe-in's a no-brainer, but how in the devil can I measure caster?
Also, is there an online reference where I can find the alignment specs for my vehicle?
best regards,
Martin
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Go to dodgetalk.com,the ball joint problem is discussed often.Or often disgusted.I am not certain about the vans but the late 90s trucks are a real problem.I hope you have a moog and not a dodge ball joint
Martin wrote:

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Fundamentally, Castor is the angle of the "king pin axis" viewed from the side, while camber is the angle of the wheel viewed from the front. You can indeed set camber using a plain level and a ruler, I do it all the time on my race car in fact. Castor is harder. I can think of a couple of fiddles to get it close, but I'd personally take a truck to an alignment shop and let them do it.
Fiddles: My race car has a flat machined on the upright so I just put a digital level on and read the castor directly. You can measure castor indirectly by measuring it's effect on camber as you turn the wheels, usually 20 degrees left and right. You could probably get in the ball park by measuring how far back the upper ball joint is compared to the lower using your level and a ruler, and compare side to side. You could do it by adjusting until the truck tracks straight - that has the advantage of ignoring what the measurement actually is and gets the effect you want.
Brian
Brian

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Turn the wheels full left and right and measure the camber change at each position. The caster is 1/2 the difference if the wheels had turned to 90 degrees so you have to do some calculation there. Since you have one that hasn't been changed, you can compare between the two sides and make them equal. It is more important to have matched caster than an absolute value.
-- Why isn't there an Ozone Hole at the NORTH Pole?
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Are you sure it was a press fit?? Most uppers in chrysler product trucks & older rear drive cars are screw in. Mabee they changed the design in the newer ones but if the joint has flat sides around the top, it's a threaded situation, which would explain it not staying put. I've welded quite a few of these that were stripped out with long lasting success but always on the vehicle. The best way to get proper alignment restored will be at an alignment shop. Good luck.
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pater wrote:

A lot of people *ruined* old Chrysler upper control arms by ASSuming they were just like other brands and pressing the screw-in joints out and new ones in.
However, Chrysler cheaped-out on the trucks in the 90s and did use press-in joints.
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Yes, they are definitely pressed in. The holes in the a-frames have smooth sides, and there are "grip ridges" but no threads on the ball joints. Some people look at the ball joints and think they are screw-in because there are flats on the outer portion, but that's deceptive. You'll quickly get tired of trying to unscrew them :)
Martin
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Geezus Christ, go get it aligned, cheapskate :) JR Dweller in the cellar and next time, buy a Ford
Martin wrote:

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That is what I was thinking too. Caster doesn't effect tire wear, but might require the driver to grip the wheel with both hands to drive it to the alignment shop.
Lane
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It's best to arrive at the shop with alignment in the ballpark. Caster and camber are highly interactive on this vehicle, ie you loosen the upper A-frame mounts and wiggle everthing around to change both settings. If they are 'way off, you're far less likely to get a satisfactory result from some guy who's used to just setting the toe-in.
Do you change your own oil? Some of us have curiousity that goes a little further :)
Martin
JR North wrote:

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I guess you didn't visit my webpage... JR Dweller in the cellar
Martin wrote:

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Nice stuff on the site. You obviously practice do-it-yourself, but somehow didn't want to preach it (at least not to me, unless you were joking).
BTW, the Datsun 2000 roadster has always been one of my favorite cars. One of my best friends from HS had one and it was fast. I'd think about selling that little 1600, though .... she obviously likes it in the rear, and that might get you killed one of these days :)
Martin
JR North wrote:

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I used to do front end work for a living- if you can drive on the rack, you can bring it back into alignment.

Front end shops have a tool for that...

Bullshit- toe is the last operation done. Vans really need to be thrust angle aligned- not a driveway job.

Do you do your own brain surgery?

Curiosity killed the cat :-(
-Carl
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Carl,
What you "used to do" is not brain surgery. Don't act like it is.
Martin
Carl Byrns wrote:

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I have had shops do front end alignments for me and I get the car home and end up redoing them in my carport with a tape and string and a level. I have yet to find a front end shop that know's how to read specs.
Martin wrote:

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Might want to check this site out. Lot of shops use it for the latest information.
www.alignmentspecs.com

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If the tire's contact patch is BEHIND the point where the "kingpin axis" would be projected onto the pavement, is this positive or negative caster?
Since I (luckily) have one side where the caster/camber is presumably correct, can I fine-tune the match using driving characteristics? In other words, if the vehicle pulls/drifts to the driver's side, which side needs positive caster reduced (assuming equal camber and level pavement)?
Thanks,
Martin
Martin wrote:

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OK, I did the homebrew alignment last night, after also replacing two idler arms and putting the best two tires on front. BTW, thank-you Dan Saitz for emailing to me the alignment specs for my van!
First, I used my 4' box-beam level to locate a level parking lot. Had to go to a church about a block from the house. On the way home, I took the van up to about 50 MPH on several smooth roads. It pulled very strongly to the left, and I thought I could hear some scrubbing from the tires.
On the driveway at home, I removed the right front wheel and loosened the two mounting bolts on the upper A-frame. These bolts ride in slotted holes in the vehicle frame, so that the front and rear mounting points can be separately adjusted by pulling/pushing toward or away from the vehicle centerline. So, you adjust caster and camber simultaneously.
I pulled the upper A-frame all the way to the outside stops. This would result in maximum positive camber (top of tire leaning outward) and an unknown (but hopefully small) amount of caster. Then I slightly snugged the front A-frame bolt to hold it in place, and pushed the rear mount toward the vehicle centerline by a "calibrated eyeball" amount to increase the caster. Then I slightly snugged the rear bolt, loosened the front bolt, and pushed the front mount of the A-frame toward the centerline by HALF of the "calibrated eyeball" amount. My idea here was to achieve a net reduction from max camber while preserving half of the added caster.
I then repeated the procedure on the left side, re-installed the wheels, grabbed a flashlight, and headed to my level parking lot for some measurements. I noticed an immediate improvement in handling. The pulling seemed to be gone, though it was hard to tell at 30 MPH on bad roads. There did seem to be a lot of "wandering", though.
With the help of my girlfriend, I made camber measurements straight forward and turning to the stops (maybe around 45 degrees) on both sides. By having her steady the vertical 4' level against the fender while I used the flashlight to watch the bubble and scoot the other end around on the ground, we were able to come up with a reference that was "plumb" (at least in the plane perpendicular to the vehicle) and within about two inches of the wheel. I made distance measurements from the vertical to the rim at top and bottom, to calculate actual camber. I calculated camber of +1.6 degrees on the right and +1.2 degrees on the left. The tops of my tires were still leaning slightly "out".
The caster calculations were more problematic because of measurement uncertainty. When the wheel was turned, this resulted in fender obscuration of the point where I wanted to set the level. So, this measurement distance was several inches further away, probably adding error. I was, however, consistent in seeing a decrease in positive camber (top of wheel tilting relatively inward) of both wheels when they were on the outside of a turn. This decrease was "maybe" 0.6 degree on one side and 1.0 degree on the other side. So, I felt I at least had achieved positive caster. Everyone says that caster is a handling factor but not a wear factor, so I figured I'd fine-tune this by road testing.
Next we took several toe-in measurements, and found the wheels to be toed out by about 1/4".
I drove back home (tools and jack were still on the driveway). I adjusted the toe to zero by shortening the tie rod on the left side (remembering the earlier drastic left pull, I was thinking about centering the steering wheel).
Time for a road test - and the van drove like a dream. No pull, all the way to 65 MPH, and the wandering (probably due to the toe-out) was also gone. You could take your hands off the wheel and it went perfectly straight. And, the wheel was centered.
Then I made a mistake. Thinking about the tire wear due to the excess positive camber, particularly on the right, I decided to make a small change and take another measurement. Since decreasing right camber would supposedly make the vehicle pull a little to the left, I thought I'd simultaneously decrease the caster on that same wheel (several references indicate that a vehicle pulls to the side with increased camber or decreased caster) to compensate.
Well, that was just too many variables to deal with when it's after midnight and the upper A-frame is free to move in two dimensions at once. My next road test had the vehicle drifting noticeably to the left. You just can't make a small, precise, "delta" change without some sort of fixed reference or simultaneous measurement.
Anyway, it took another round of wrenching (and was about 1:15 am) before I had the driveability back to where I was satisfied.
This weekend I'll try another idea for fine-tuning the camber, which is still excessive by anyone's account. I'll use a magnetic-base stand from a dial indicator to position a pointer directly above the grease fitting of the upper ball joint. That way, I will be able to tell exactly how much relative shift I've made in the A-frame before re-tightening the bolts.
Yes, it was a lot of work, but I really feel good about the learning experience.
best regards,
Martin
Martin wrote:

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The pointer and magnetic base trick worked perfectly. I took measurements, removed the wheel, installed the pointer, and then made the necessary relative adjustments. The van drives perfectly, no pulling, no wander, etc. I'm not even going to take it to a shop for any fine-tuning, as there's no way they could improve on the driveability, and the current settings should minimize tire wear.
I'd recommend this method to anyone who wants to try a do-it-yourself alignment.
best regards,
Martin
Martin wrote:

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