Getting your Jeep
aligned can often be more than a headache. We often hear: 'Tires are too large
for our machine', 'we don’t do lifted Jeeps', and 'we do not know how to adjust
control arms', etc are just some of the stories.
Adjusting caster on our Jeep TJs is not only simple, but you can do it yourself in your driveway.
The angle between the vehicle's steering axis and a vertical line, as viewed from the side, measured in degrees.
It is CRITICAL that the Angle Finder [available from Sears, Home Depot, ACE, about $10 or less] be ALIGNED and parallel lengthwise with the Jeep frame and wheels.
You MUST be looking at the angle finder (AF) straight on to get an accurate reading. Try looking at it and moving your head slightly to the left and right of the angle finder. You will see it shift back and forth, this will help you identify the exact angle. Might want to practice by setting your angle finder on any flat surface that you can easily move back and forth while looking at it.
Discovered this Digital Multifunction Torpedo Level Mdl
48295, at Sears. It reads to an accuracy of .1 and displays to .1 degree. It does several other things such as a lit screen and what is really COOL is the display automatically flips to read correctly when you turn it upside down.
It has a powerful magnet on the bottom and will provide some very accurate readings for Caster measurements over the Home Depot angle finder.
Got it at Sears on sale for $20, regular $34.95
Alignment machines can get far more accurate readings. Most will at least give 2 decimals points, some can do even 3, 4.589 for example. Looks impressive, but its most likely a waste. Adjustment ability is only about a half degree in most cases.
Bottom line is you can get just as good results as the alignment shop. I would not recommend using your driveway unless you know it is level on level ground, your garage floor might be a better place unless it has also been sloped for water runoff.
Set Caster (using adjustable upper/lower control arms):
To DECREASE CASTER ( - ):
Lengthen the upper control arms and or shorten the lower.
To INCREASE CASTER ( + ):
Shorten the upper control arms and or lengthen the lower.
Next time you see a motorcycle, look at the way the front wheel is kicked out in front of the bike this is positive caster.
Shopping cart with floppy wheel, and wheels are behind the vertical, this is negative caster.
The difference in side-to-side between caster settings. More than half a degree difference may cause a steering pull toward the side with the least caster. Caster on the left front wheel is sometimes decreased to compensate for high road crown.
1) Park Jeep on a flat hard surface with wheels straight and parallel to the frame
2) Place AF on bottom of knuckle at outer end of front axle, insure the AF is parallel with the direction of the Jeep wheels and frame
3) Write down angle
4) Do same on opposite side
5) Write down angle
6) Remove end of control arm that you can adjust and count each full turn. For a starter, do 4 or 6 full turns, replace control arm and measure the change in angle. Example: 6 full turns resulted in 3 degrees. Therefore, each full turn = 1/2 degree, each 1/2 turn = 1/4 degree. Applies to JKS 18 TPI Control Arms, but most will be close