Im understanding toe and camber but cant get a grasp on how we set castor on our older mopars.our car is dedicated drag car with new upper arms new qa1 kframe with new lower arms new adjustable strut rods new spindles and strange disc brakes.i guess I dont understand of we move the upper ball joint to get a pos. Castor reading.been searching the net but still not understanding the castor adjustment. Thanks steve
front end alignment
- Thread starter swifter
- Start date
-
The easiest way to explain caster is the tilt of the upper ball joint, forward -negitive caster,, to the rear,+positive caster. On a mopar this is done by rotating the cams on the upper control arms. To gain +positive caster rotate the front cam out,the rear cam in. If you move the cams equal amounts camber should stay close to your original setting. You also can gain caster by using the adjustable strut rods by shorting the rod. Do not try to gain all the positive caster by using the strut. Use the cams first,then if needed gain more with the strut. You don't want the strut to bind.
Clear as mud? I see it in my head and did the best to put it in words.
Clear as mud? I see it in my head and did the best to put it in words.
67Dart273
Well-Known Member
Possibly what is confusing you is the way caster is MEASURED. Caster cannot be "directly" measured. You do so by measuring the CHANGE IN CAMBER over a sweep of so many degrees in steering change. The caster / camber gauges have a built in "math factor" for this.
BASICALLY what is happening, is that as you sweep the wheel left to right, and measure camber, it CHANGES because of the tilt of the caster. This change is multiplied depending on the degrees of sweep. In essence, the old caster / camber gauge like my old Ammco, is nothing more than a camber gauge with a built-in circular slide rule to compute caster
To put this another way, you don't NEED a castor gauge. All you need is an accurate level which will give you degrees of tilt, in other words, CAMBER.
So you would use a simple protractor, looking straight down at the wheel, to show wheel steering angle. "Steer" the wheel out 20 degrees. Note the camber tilt angle (or zero your gauge)
(In the photo below, the turning plates have a built in protractor. You cannot see it because these are so old and beat, LOL)
Rotate the wheel IN 20 degrees and note the amount of change from the first reading.
Multiply this change X 1.5 (for 20 degrees) and that IS your caster
There are charts and formulas you can Google. I guess? some cars or some tests won't allow 20 degrees of change, so there is a formula for other angles.
This is my old Ammco gauge
http://www.forabodiesonly.com/mopar/attachment.php?attachmentid=1714605536&stc=1&d=1364415442
The blue scale is connected to the mechanism, and tilts the level. THAT is what shows you the degrees in / out of tilt for camber.
The red scale IS NOT connected and simply rotates. You hold the two together when making caster measurements, and rotate them together. The red scale is simply a math display of the blue scale X 1.5
BASICALLY what is happening, is that as you sweep the wheel left to right, and measure camber, it CHANGES because of the tilt of the caster. This change is multiplied depending on the degrees of sweep. In essence, the old caster / camber gauge like my old Ammco, is nothing more than a camber gauge with a built-in circular slide rule to compute caster
To put this another way, you don't NEED a castor gauge. All you need is an accurate level which will give you degrees of tilt, in other words, CAMBER.
So you would use a simple protractor, looking straight down at the wheel, to show wheel steering angle. "Steer" the wheel out 20 degrees. Note the camber tilt angle (or zero your gauge)
(In the photo below, the turning plates have a built in protractor. You cannot see it because these are so old and beat, LOL)
Rotate the wheel IN 20 degrees and note the amount of change from the first reading.
Multiply this change X 1.5 (for 20 degrees) and that IS your caster
There are charts and formulas you can Google. I guess? some cars or some tests won't allow 20 degrees of change, so there is a formula for other angles.
This is my old Ammco gauge
http://www.forabodiesonly.com/mopar/attachment.php?attachmentid=1714605536&stc=1&d=1364415442
The blue scale is connected to the mechanism, and tilts the level. THAT is what shows you the degrees in / out of tilt for camber.
The red scale IS NOT connected and simply rotates. You hold the two together when making caster measurements, and rotate them together. The red scale is simply a math display of the blue scale X 1.5
FJ5
Well-Known Member
My head hurts.
I use one of these....video shows how they measure caster....same way no matter what gauge you use.
[ame="https://www.youtube.com/watch?v=cu5xEFdDr7M"]91000 - Fastrax Camber / Caster / Toe Gauge - Specialty Products Company - YouTube[/ame]
[ame="https://www.youtube.com/watch?v=cu5xEFdDr7M"]91000 - Fastrax Camber / Caster / Toe Gauge - Specialty Products Company - YouTube[/ame]
67Dart273
Well-Known Member
You do have to be patient, take your time, get some of the right tools, and "fiddle."
If you move, example, the rear of the A arm in, THINK what this does. This pulls the rear of the A arm IN
So this is going to tilt the wheel IN some, but it is ALSO going to affect caster, because it will "tilt" the top of the spindle towards the rear, or "lean it back."
If for example you are trying to adjust camber without affecting the caster, you need to pull BOTH A arm adusters in or out "the same amount."
"Good luck with that."
On the other hand, if you ARE trying to tilt the spindle towards the rear (example) but have the camber 'about right' and don't want to affect it, then you would pull one adjuster "out" and the other "in"
"Good luck with that."
It takes a lot of patience, and a lot of back and forth.
AND if you "forget" to get one adjuster tight and it slips, well.............
1...Set the ride height (read the shop manual)
2..."Rough" in caster and camber together, then back and forth 'till then are right
3...Last set toe
Read this if you have not. Use the "skosh" chart if you have radials
http://www.allpar.com/history/mopar/front-end-alignment.html
If you move, example, the rear of the A arm in, THINK what this does. This pulls the rear of the A arm IN
So this is going to tilt the wheel IN some, but it is ALSO going to affect caster, because it will "tilt" the top of the spindle towards the rear, or "lean it back."
If for example you are trying to adjust camber without affecting the caster, you need to pull BOTH A arm adusters in or out "the same amount."
"Good luck with that."
On the other hand, if you ARE trying to tilt the spindle towards the rear (example) but have the camber 'about right' and don't want to affect it, then you would pull one adjuster "out" and the other "in"
"Good luck with that."
It takes a lot of patience, and a lot of back and forth.
AND if you "forget" to get one adjuster tight and it slips, well.............
1...Set the ride height (read the shop manual)
2..."Rough" in caster and camber together, then back and forth 'till then are right
3...Last set toe
Read this if you have not. Use the "skosh" chart if you have radials
http://www.allpar.com/history/mopar/front-end-alignment.html
Thanks 67--My head doesn't hurt it just makes me giggle in a weird way.straight forward explanation but confusing at the same time,I think its one of those times where you just have to do it and experience it.THANK YOU--Steve
Yes we set ride height last night and i'm sure we'll have to adjust after Zach does a few wheel stands on take off,right now well before the up-dates it was a nice 12-18 in lift on the front tires it's just the front end was wasted and the previous owner didn't do a damm thing to it,We respect the car more than that and are giving it the respect a 30yr old drag car deserves--Steve
-
