We need to be careful here. The driveway angle does not affect caster one iota. Caster is the angle of the steering axis tilt forward or rearward in relation to the vehicle's centerline, not in relation to the floor, or ground. Take the letter "T" as an example. If the letter's base affects the angle of intersect, then that angle would change with the changing angle of the base. It does not. The letter "T" has a 90 degree interscet whether it is upright, angled, or upside down. We could assume then, that the intersect of that letter "T" is our steering axis. How that axis is angled is only measured and compared to the verticle (horizontal on our Jeep) line. In other words, the caster angle on our letter "T" would be the tilt of the horizontal crossbar that makes the "T". Since we are only comparing that angle to the verticle bar, the base (floor or driveway) has no affect whatsoever. Now, if you are talking about how alignments were done 30 or so years ago, then yes, the floor would have an affect. Modern day alignment machines use lasers and the like to find the true vehicle centerline and compare from THAT. Doing so eliminates any chance to get the alignment wrong due to an uneven vehicle stance.

 

If he is measuring it in his driveway, he probably doesn't have modern day laser equipment. That is just an assumption on my part though!

 

"I am using a simple angle finder for measurements."

I assume that means a cheap angle finder. Like the one I have. *L*

 

Yep - no lasers in my driveway! Just a simple magnetic circular angle finder. When I draw my set up on paper, I think I get the answer I need.

 

Doesn't matter what he's using. Caster does not change. That's like saying "when you go up a hill, caster changes." It doesn't happen. Caster is a fixed adjustment unless you readjust it or something else changes....such as a wreck or the like. I completely understand that he's in the driveway. But yall need to understand, even when measuring with simplistic instruments, caster is what it is. It is a comparison of angles. Those angles are the steering axis compared to a verticle line through the axle centerline that is perpendicular to the vehicle centerline. THAT is what caster is. The only thing that changes is method of measurement. In fact, he would get the same reading if he knew exactly what angle the vehicle centerline was, and installed the angle finder at that angle, instead of level with the driveway.

 

i'm not arguing what caster is, just that with a simple plumbob type angle finder, the angle you view will change when you change the angle the jeep is at, because it mounts to the Jeep.

if my jeep is set to 5°, and sitting on a 20° slope, and i put the angle finder on it, im going to read 25°, not 5°. That's all I am pointing out.


Using a simple angle finder, you would need some reference, most (if not all) of the directions to adjust it, assume you are sitting level.

 

Not meaning to argue either....and yall are RIGHT for comparison's sake. All I am saying is that for TRUE caster measurement, the JEEP is the base, not the ground. That's all.

 

Good post from the stand point that we all revisited the castor isssue and I got the answer I needed!

Thanks!

 

That's all that counts!

 

Its a frame of reference question. The gravity angle finder always measures relative to gravity. If the jeep is at an angle, the jeep angle must be subtracted(or added, depending on orientation) to calculate the caster.