Stock Rubicon Caster

Zevulin

Zevulin

New member
Just for the heck of it I threw an angle finder on to check my stock caster pre-lift install, made sure the angle finder was calibrated and I'm showing 3* caster, is this possible from the factory?
IMG_3383.jpg


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If your holes at the front of the pumpkin are reading 87, that actually means you have closer to 5 degrees caster. If the front reads 88, you have 4. Basically, if your pumpkin is 2 degrees pointed back, the caster at your ball joints is around 4.2 degrees. This is assuming the ground you're parked on is a perfect zero.
 
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WJCO said:
If your holes at the front of the pumpkin are reading 87, that actually means you have closer to 5 degrees caster. If the front reads 88, you have 4. Basically, if your pumpkin is 2 degrees pointed back, the caster at your ball joints is around 4.2 degrees. This is assuming the ground you're parked on is a perfect zero.
Click to expand...

89 would be 5


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Zevulin said:
89 would be 5


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Click to expand...

If the ground you're parked on is a perfect 0 and your front diff holes are at a perfect 90, your caster would be 2.2 degrees.

If the holes are at 89, your caster would be 3.2 degrees.

If the holes are at 88, your caster would be 4.2 degrees.

If the holes are at 87, your caster would be 5.2 degrees.

And so on.......

If I'm wrong, please someone correct me, but I'm pretty sure this is accurate.

EDIT: THIS IS NOT CORRECT, SEE MY POST BELOW.
 
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Zevulin said:
It's level best I can tell, it's an indoor parking garage.
Click to expand...

Meaning it's NOT level.

If you want to get an accurate reading of what you're seeing now, get an alignment. They'll give you exact readings on your Jeep as it sits now.
 
WJCO said:
If the ground you're parked on is a perfect 0 and your front diff holes are at a perfect 90, your caster would be 2.2 degrees.

If the holes are at 89, your caster would be 3.2 degrees.

If the holes are at 88, your caster would be 4.2 degrees.

If the holes are at 87, your caster would be 5.2 degrees.

And so on.......

If I'm wrong, please someone correct me, but I'm pretty sure this is accurate.
Click to expand...
There's a 6* angle between the pinion axis and steering axis, if the pinion is at dead zero the caster would be 6*.
90=6
89=5
88=4
87=3
So on and so forth.
IMG_3384.JPG


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Zevulin said:
There's a 6* angle between the pinion axis and steering axis, if the pinion is at dead zero the caster would be 6*.
90=6
89=5
88=4
87=3
So on and so forth.
View attachment 255734


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Click to expand...

Ok. I think I confused the gauge readings regardless between 88 or 92. And if indeed this is is a JK axle, then I am incorrect with the starting caster if pinion is at 0. But, as far as caster goes, the caster angle increases as your pumpkin tilts back. So if you were at 89 degrees on the pumpkin at the spot in your picture, your caster would actually be 7 (assuming ground is 0). For every degree the pumpkin tilts backward the caster increases one degree. Per the alignment writeup thread, if your sitting right at 92 and ground is 0, you would be at a rough 4 degrees. 91 would be 5, 90 would be 6, 89 would be 7.
 
WJCO said:
Ok. I think I confused the gauge readings regardless between 88 or 92. And if indeed this is is a JK axle, then I am incorrect with the starting caster if pinion is at 0. But, as far as caster goes, the caster angle increases as your pumpkin tilts back. So if you were at 89 degrees on the pumpkin at the spot in your picture, your caster would actually be 7 (assuming ground is 0). For every degree the pumpkin tilts backward the caster increases one degree. Per the alignment writeup thread, if your sitting right at 92 and ground is 0, you would be at a rough 4 degrees. 91 would be 5, 90 would be 6, 89 would be 7.
Click to expand...

Caster decreases as you tilt back the pumpkin, at least that was my understanding. Maybe someone else can weigh in to clear this up.


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WJCO said:
Absolutely not true. That I'm 100% sure of.
Click to expand...

If the angle between the pinion and steering axis is set at 6* and does not change, explain how tilting the pumpkin back will increase the caster? If the pumpkin and steering axis rotate in opposite directions when adjusting then this would be true, do they? I thought the 6* angle was a fixed angle between the two irrespective of caster. I'm new to all this so I certainly could have misunderstood.


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Zevulin said:
If the angle between the pinion and steering axis is set at 6* and does not change, explain how tilting the pumpkin back will increase the caster? If the pumpkin and steering axis rotate in opposite directions when adjusting then this would be true, do they? I thought the 6* angle was a fixed angle between the two irrespective of caster. I'm new to all this so I certainly could have misunderstood.


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Click to expand...

It's a solid axle, so if pinion angle changes so does caster. They rotate together, they have to, the inner knuckle is welded on to the axle tube. If pinion points down more, caster goes up. If pinion points up more, caster goes down. If your ball joints were 100% straight up and down, you would have 0 caster, as your pinion points down, this forces you ball joint axis line to point back, every degree this occurs is one more degree of positive caster. So at 0 pinion, the caster is positive 6.
 
That's correct, so if you rotate the pinion up 2* the caster would be positive 4*. The reading on my pinion is 3*, so my caster is positive 3* as indicated in the original post. Not sure what the confusion was. Thx for the info!


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Yes! If its still factory chances are the surface your Jeep is sitting on in not level. Stock caster is 4.2* (pinion pointed up 1.8*). Put you angle finder on the ground and zero it out then place it on your pinyon flange (Most accurate place to measure from) and double check your readings. When do this and measure it in the same place after you install your lift and make adjustments as necessary to get it as close to stock as possible.
 
jesse3638 said:
Yes! If its still factory chances are the surface your Jeep is sitting on in not level. Stock caster is 4.2* (pinion pointed up 1.8*). Put you angle finder on the ground and zero it out then place it on your pinyon flange (Most accurate place to measure from) and double check your readings. When do this and measure it in the same place after you install your lift and make adjustments as necessary to get it as close to stock as possible.
Click to expand...

Thx!
Ultimately like you wrote, the baseline reading on the angle finder is inconsequential as long as the reading is taken before and after with the Jeep in the same location, then adjust caster accordingly post lift.

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