Different front end alignment question

[walker]

I am about to put in my new, rebuilt, disk brake front end. I can figure out how to get a basic alignment on the truck as far as camber and toe in, but cant figure where, or how to measure for a caster adjustment. I figured at worst I could use a protractor to measure the current spindles between the two ball joints, then just apply that measurement to the new front end. I do wonder if there is an accurate way to get the exact measurement though?
Any suggestions?
Thanks.

[Rooster's 67]

NOT to be a smart aZZ but yeah take it to an alignment shop.
Uh yes there is a way to take measurements for caster without an alignment machine but it would be hard to describe. it involves a turntable for the wheels and a special tool that attaches to the hub. the tool has a level and degreed markings to measure the tilt in and out of the wheel when turned to a certain degree both ways. at both turns you re-level the tool and take readings. then calculate the caster. trust me, let the guy with the $40K+ machine set up your front end. comes out cheaper in the long run in tire wear.

[68 short step]

i agree dont attempt to do it yourself without proper alignment equiptment. i promise you i wont be right ,if you eye ball it.

[cdowns]

the cost of a professional alignment is ALOT LESS than the cost of a set of tires worn out by a halfassed home alignment

[neonlarry]

I would not worry too much about caster. Its almost impossible to set it yourself and if its off a little it won't affect tire wear. What it will affect if its off and you have manual steering is effort required for initial turn-in and how easily the wheel returns to center. If you have power steering you probably won't notice. But like said above get a professional alignment. A home alignment if fine if you know what you are doing and have the proper tools but most people don't.

[cableguy0]

i agree with the others. this is not a place to try to save money. get it close as you can then go get it aligned.

[Rooster's 67]

get the toe-in set close and camber set close to straight and drive it to the alignment shop.

[walker]

Don't get me wrong, this is not about saving money. I just hate not being able to figure out a way to do something myself. In fact, now that every body says, and I will take it to a front end shop in the end, I guess I will HAVE TO figure out how to do it myself!
My chief question still stands though, where does the caster angle measurement come from. On a solid axle it is the kingpin angle and is easy to find. On these independant front ends it looks like it is the rake of the angle of a straight line drawn through the ball joints. The problem is that the spindle is offset from that line, so perhaps it is the difference in angle from the line through the balljoints(kingpin angle) and the line from the upper ball joint and the spindle. Just speculating here though. If anyone has the actual answer I would love to find out.

[Portmod7]

It is the angle of the line strait through the center of the ball joints from front to back on the truck, whereas the camber is from left to right on the truck. Positive caster has the upper ball joint behind the lower(which is what you want). I did an allignment on a 64 falcon, but i had the tools the one guy described, a set of turn tables and a gauge that sticks to the hub with a magnet. Those tools are very expensive and I highly doubt you get it right without them. I have heard of an "oldschool gauge" that you can take measurements off the wheel with, but I dont know where or how to get ahold of one, or even what it looks like. All I can say is, better have a lot of time on your hands!

[Rooster's 67]

here is a pic of a caster/camber gauge, not all that expensive by any means, just requires turntables to go with it, also makes it hard to align with thrust angle, but accurate measuring can get that close. you wont have any pulling or excessive road drift with less than 1.5 deg. cross caster.

here is a link to the websitehttp://www.paragon-products.com

[Rooster's 67]

here is more info on setting up caster and alignments(al-beit circle track)but alignment is alignment.http://circletrack.com/howto/138_030...caster_camber/

[walker]

AAAHHHHhhhhh, here is a quote off of the webpage that rooster sent. Now I understand the need for a turntable, and why the directions for doing it are so hard to come by. If I find a way to do it when I am under there(it will be a few more weeks as I just had surgery) I will let you know. At the very least this has been very educational, thanks for all the responses.



"Caster Defined Caster is a design condition that, in addition to the spindle kingpin angle, serves to cause a wheel to want to track straight ahead as a product of weight being applied to the wheel structure. A common example is a bicycle front wheel and fork assembly. The tube on which the handlebars are mounted is placed in a set of bearings above the fork. From a side view, this tube is angled so the bottom bearing is ahead of the top bearing. If we turn the front wheel to 90 degrees from the direction of travel, it will want to return to straight ahead because of the effect of caster. The same effect is present in the front wheel assemblies of our race car.

What Caster Does To ease the amount of effort it takes to turn the wheel in our race cars, caster split was introduced into the design. Split means that we set different caster amounts into each wheel assembly so the car will want to turn to the left and thereby reduce the amount of effort it takes for the driver to hold the steering wheel when negotiating the turns. Proper split for circle track racing means the left-front (LF) wheel will have less positive caster than the right-front (RF) wheel. In some cases, teams have been known to set negative caster in the LF wheel and positive caster in the RF wheel.

To measure caster in each wheel, we use a caster/camber gauge. This tool attaches to the wheel hub. To check the amount of caster, we need to follow these instructions:

1. Attach the caster/camber gauge to the RF wheel hub first.

2. Turn the steering wheel to the right so the RF wheel has turned exactly 20 degrees.

3. Level the gauge and set the adjustable caster bubble vial so the bubble is at the zero mark on the caster side of the tool.

4. Turn the steering wheel to the left so the RF wheel is turned past straight ahead and ending up at left from straight ahead by 20 degrees.

5. Again, level the gauge, note the location of the bubble on the scale, and record the amount of caster in the RF wheel.

6. While the wheels are still turned left 20 degrees, remove the caster/camber gauge and place it onto the LF wheel hub.

7. Level the gauge and set the bubble on the caster gauge to zero.

8. Turn the steering wheel to the right past straight ahead until the LF wheel is turned 20 degrees to the right of straight ahead.

9. Level the gauge and read the caster gauge to see how much caster is in the LF wheel.

Adjusting Caster To adjust the amount of caster in each wheel, you will need to move the upper ball joints fore or aft. To increase the amount of positive caster, move the top ball joint toward the rear of the car. Some cars have slots cut into the upper chassis mounts for this purpose. If you have permanently attached vertical mounting plates for attaching the upper control arms, you can vary the amount of shim spacing for each of the bolts that attach the control arm to the chassis. Wider spacing at the front bolt (control arm shaft inside of the mounting plate) will move the upper ball joint to the front, creating less caster at that wheel and so on. This, however, is not the preferred method. Once you have established the exact caster amounts for each wheel using the above method (if not using slotted control arm shafts), you should order an upper control arm that has the ball joint offset to give the correct amount of caster at each wheel. That way, you can use the same shim spacing for each mounting bolt to connect the upper control-arm shaft to the chassis.

In today's complex world of chassis setup, we cannot overlook the importance of properly adjusting our car's front geometry settings. Caster and camber are a major part of that equation.


Positive caster in the front wheel assembly is created when the ball joints are offset (from a side view) so the upper ball joint is farther to the rear of the car than the bottom ball joint. The degree of caster is related to the angle in degrees that a line through the ball joints forms from a vertical line.


Set the bubble at zero on the caster side of the gauge. Some teams use one edge of the bubble so reading the angle is more accurate than trying to estimate the center of the bubble.


To measure on the floor to get exactly 20 degrees of steering, cut a 30-inch piece of 1-by-6-inch wood or similar straight, flat piece and lay it against the tire. Mark midway on the wood (15 inches) and line that up with the hub. Mark the outside corner of each end of the wood. Turn the steering wheel until the ends have moved 53/16 inches and you will have turned the wheel 20 degrees.


Some cars have the upper control-arm mounts cut with a slot that makes adjusting caster easy. Some upper control arms are also slotted for the same reason. If your mounting plates or control arms do not offer this method of adjusting caster, you can angle (from a top view) the control arm shaft by moving shims front to rear. This is not the ideal method, but will work until we can find the right caster split that suits the driver. We can then order offset control arms that will locate the upper ball joint for proper caster without needing to angle the shaft.






Move camber adjustment shims back and forth from each mounting bolt, or slide the control arm shaft if it is slotted, to adjust the amount of caster in each wheel. This will move the upper ball joint forward (to reduce caster) or to the rear (to add caster).
After you have leveled the gauge, read the center of the bubble on the camber side of the gauge to get your wheel camber setting. Make sure the car is at ride height with all of the weight in the car including the driver. Air the tires to operating pressures. These settings may change once the car is raced and the tire temperatures have been evaluated."