Alignment stuff

So, hiw do we accurately measure caster at home?

After being at the mercy of my towns alignment guys and never being happy, i need to learn. Caster us the one that always kicks my ass.

Ive got a digital angle finder that does camber well, and a tape measure for toe. And four cars that need alignments. A 95 Silverado, 06 mazda5, 1999 miata, 70 duster. 

For my S10, this thread covers what I did.  Wasn’t terribly difficult, but boy was it tedious.  I have not had a chance to really drive it and see how it does, though.

You can calculate it by the recording camber and toe with the wheel steered one way and then steering the opposite way and recording that. After you've done it this way just once you'll pay for that fancy camber/caster gauge that does the math for you. I used to do it that way and it's really tedious.

GRM Live did the camber calculations w/o gauge on their Vette IIRC

I don't, I use a Hunter 4 wheel alignment rack and computer

Faster and Accurate 

Honestly, for caster, you can probably set it pretty well by feel.  Go for whatever feels right and doesn't make the car pull to one side (which uneven caster can cause).  Doesn't really matter if it's 3 or 7 as long as it feels right when you drive it and the car behaves how you want it to. 

look at vehicle from the side. 

Upper ball joint should be behind (i.e. rearward of) lower ball joint.

you need to know the horizontal distance that the UBJ is behind the LBJ.  And you need to know the vertical distance between UBJ and LBJ.  

Caster angle is the angle who's tangent is equal to (horizontal distance divided by vertical distance).

Center the steering.  Measure distance from ground to some point on LCA as far outboard as you can.  Call that distance A.  Measure distance from ground to some point on the front frame.  Call that distance B.  Subtract A from B.  Jack up vehicle the same amount front and rear.  Measure from ground to B again.  Subtract old B from new B.  Remove front wheel.  Remove front spring and jack up under LCA until new A minus old A is equal to new B minus old B.

Drop a plumb from LBJ to floor and mark it.  Then drop a plumb from UBJ to floor and mark it.  That gives you the horizontal distance from UBJ to LBJ at ride height.  Now, measure vertical distance between UBJ and LBJ.

open the calculator app on your phone and key in horizontal distance / vertical distance = .  Then hit either "Atan "or "tan-1" or (on iPhone) "2nd" "tan" and you'll get a number.  I think the default is degrees.  You can check by taking tan-1 of the number 1.  If the answer is 45, you're in degrees.  If the answer is 0.788, you're in radians and need to multiply by 57.1 to convert to degrees.

easy peasy.

In reply to AngryCorvair :

I know you are speaking English. I know most of the words. But you completely lost me.

Tims thread, with measurements at opposite 20 degree angles makes sense and seems repeatable. Will that method be good enough for good driving characteristics and tire wear?

In reply to Dusterbd13 :

You don't have to make it 20 degrees (unless you're using a gauge that explicitly expects a certain steering input). It can be any level of steering, the math takes care of it for you. When I used to do it manually I would just turn the steering wheel 90*from center which was pretty repeatable and doesn't require marking out angles and such on the floor.

For caster I use an old school camber/caster bubble gauge I bought from some racing supplier for cheap.

I just turn the wheel one full turn either way.  For the left wheel, turn the steering wheel to the left one full turn, zero the gauge, then turn the wheel one full turn to the right (from center), and read the gauge. It doesn't matter how far your turn the wheel unless YOU need a specific and accurate number.  If YOU are consistent, it doesn't matter; all you need to to make them the same (and probably maximum).

For toe, I use toe plates and two tape measures, and I've been every bit as consistent and as repeatable as a shop.

I did own a John Bean 4-wheel alignment machine for a while, but because of the setup time, it wasn't as fast as the old-school way. I traded it off for labour.

In reply to Dusterbd13 :

yeah, without pictures it's a wall of words to anyone who isn't me.  sorry about that.

Tim's method is good.

Since i already have a digital angle finder, i cant see a reason to buy the 15 dollar magnetic camber tool on ebay. Other than its on a stick style magnet to attachdirectly to the spindle or rotor.

Anyone build a jig that mounts to the wheel to lay the angle finder on? My precision 2x4 doesn't seem adaquate any more. And it hits the spikes in every eheel that isnt a 15 inch mopar steel wheel. (Thats what i made it for.....)

Im looking for a solution to implement across the board. Like an adjustable peace sign or something. Never held any of the commercially available stuff in my hands, so i dont have any clear ideas how to make something. 

We all know i can work with wood or steel, and have plenty of scrap for both. Bonus points awardedfor something that will hold itself in place, or a stupid cheap commercially available option. 

I use a variety of carefully trimmed lengths of 1x1" square tubing to lay against the rim. I've cut some for 13", 15", and 16" wheels.  I have a digital gauge which sticks magnetically to that, I just don't like thinking "88°" instead of "-2°."

I have both; I use either.

You could hold the tubing on with bungie cords on/through the rim.