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Unread 01-23-2007, 12:21 AM   #1
jode
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Caster angle question

Is this an accurate way to measure caster?



If it is, then I have a problem. it is hard to see in the pics, but it is registering 1.75-2.5 degrees of caster (give or take a degree or two.)

Also, for those of you that have played around with shackle length, is there any kind of estimation on how many degrees of caster are added/subtracted per inch of change to the shackle length? I'm trying to figure out if I reduce my shackles by an inch or two, how much that will affect my caster.

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Unread 01-23-2007, 04:49 AM   #2
iengle
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Accurate? No, but a decent way to get a starting point. You really need to know the angle from ball joint to ball joint -- if there are any caster sleeves in the upper, you can't measure that from the outside of the inner C.

Bring out the old geometry skills and I'm sure you can figure out the change in caster by length of shackle. But, the best suggestion is going to be to go with the shortest shackle as possible and get your lift by a better route (spring, SOA, etc.).

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Unread 01-23-2007, 05:01 AM   #3
CJ51973
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That is probably OK what your showing. I typically go with the bottom ball joint. You'll need to take the zerk out to do it.
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Unread 01-23-2007, 09:17 AM   #4
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There is some great info here:

http://extremegarage.com/techtips/stechtip.htm
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Unread 01-23-2007, 10:25 AM   #5
jode
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Quote:
Originally Posted by CJ5_Fan
There is some great info here:

http://extremegarage.com/techtips/stechtip.htm
You are correct...like this for instance:

Quote:
The reason we have an offset angle between upper and lower spindle points is to allow optimum steering and handling for a given vehicle. A positive caster angle is used to allow predictable steering of the vehicle. If the caster was zero with the upper ball joint exactly above the lower ball joint, steering would be erratic, the vehicle would be very hard to control and the front wheels would wander all over the road. By creating a backward 'lean' (a positive caster angle), the vertical travel of the front wheels is 'dampened.' The more positive the caster angle, the more controllable the vehicle is at higher speeds. As caster is lessened (closer to zero), the vehicle's front wheels will react faster to steering input, but highway stability will be decreased.
But that isn't really pertinent to the question of the best way to measure caster when the axle is assembled and you can't get to the balljoints....
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Unread 01-23-2007, 03:10 PM   #6
jeepin in maine
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any variance in the width of the knuckle from top to bottom will throw your reading off.best way is to pull a zerk fitting and put your angle finder on the top or bottom balljoint
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Unread 01-23-2007, 03:19 PM   #7
jode
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I'll do that - thanks.
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Unread 01-23-2007, 04:35 PM   #8
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I want to say the top part of the "C" is a little narrower than the bottom so that's gonna throw you off a bit. Like mentioned already, go from the flat on the bottom ball joint....
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Unread 01-23-2007, 04:41 PM   #9
jode
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If anything, then, yes, the top would be more narrow....which means I may be running closer to zero caster. No wonder it wanders all over the road...
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