is this a feasable way to measure castor?

Could a simple way to check for 0 degees castor be attempted by merely putting a bubble level against the bolts on the front axle pumpkin?
Another question: By lowering front spring shackles increase positive castor?
In my opinion, yes to both, but would like input....

Mike in KC

 

Hi,

No that sounds incorrect. A angle finder on the front axle cover bolts is only telling you pinion angle, since the front housing surface is perpendicular to the pinion shaft bore and most always not parallel with the caster of the steering knuckles.

Your second question is unclear to me what you are asking, but here's an answer that may help, and a bunch of jargon afterwards that may or may not help!... When longer shackles are installed on a jeep that still has the shackles in front of the axle (not a shackle reversal as on some military jeeps) positive caster is lessened and the caster may even be reduced to 0 degrees or even moved to negative caster with too long of a shackle, and when shorter shackles are used, positive caster is increased.

Most jeeps that I build axles for have the casters set to between 3 degrees and 7 degrees of positive caster as the axle sits when mounted in the vehicle. Caster that is less than these measurement or negative can cause adverse handling and wandering of the jeep while driving.

Caster is the angle of an imaginary line that passes through the centerline on the axle kingpins as viewed from the side of the vehicle relative to verticle. Positive caster is present when the lower kingpin's center is forward of the the upper kingpin's center. A rough measurement of caster can be made by placing an angle finder on top of the kingpin bearing caps and measuring the angle parallel to the frame, viewed from the side of the vehicle.

Camber is the angle of an imaginary line that is drawn through the centerline of the front tires as the vehicle is view from the front or back, and is measured in degrees relative to a verticle line. Most older jeeps have a pronounced camber, visible as the tops of the tires leaning outwards when the jeep is viewed from the front.

Finally kingpin inclination angle is different from camber in that it is the angle of the line drawn through the kingpin centers, relative to verticle as viewed from the front or back of the vehicle. It's important to note that camber and kingpin inclination are two separate measurements, although they are often considered unadjustable.

Hope this helps,
Daniel Pawlak

 

wow....thanks for clearing that up. Your second paragraph nailed it on what i was asking about the shackles. I have rather long ones on there now, and just by eyeballing things, I seem to have some negative castor as a result. I was thikning about putting the stock length shackles back on and was wondering if this would help with the castor situation.
If I am understanding you, 0 degrees would be the top of the kingpin caps and the borttom of the frame being exactly paralell?
While on the subject, The PO put a 4" spring lift on the vehicle, and the only shims that I've seen are on the rear axle. I assume to help unbind the rear drive shaft? Should I leave them there due to the life and try to find some more for the front as well? Wouldnt the addition of shims on the front cause binding of the front driveshaft?



Thanks for all the input
Mike in KC