Measuring castor/pinion angles

[XJ858]

Ok, my eyes are starting to bleed from searching through countless threads. I'm installing Full Traction adjustable UCAs and have a problem determining the correct castor/pinion angle I should come up with. After searching I found out the ideal caster angle is anywhere from 5.5 to 7 degrees and the pinion angle should be around 3 to 4 degrees.

Now the question is, are these numbers correct? (my lift kit should net me about 5.5 inchs of lift) And secondly, how do I measure castor angle? I have an angle finder but not really sure what I should be looking at. Do I measure the angle through the steering knuckle compared to a level plane? And if so what is 6 degees postive castor? is the 6 degrees to the front of the vehicle or to the rear?

I think I can figure out the pinion angle to the driveshaft eaisly enough assuming my target numbers are correct. Is there anyone out there that can give me a quick lesson in castor geometry?

[XJCreeper]

Here's a couple bookmarks I keep:
http://go.jeep-xj.info/HowtoAlignment.htm
http://www.cowtownjeeps.com - (under Tech info)

Of couse it with be different for you setup. But this will give the basics. I measure my castor at the top ball joint on the flat spot.

[twisted_ed]

Well like many I am a firm believer that Pinion angle is more important than pinion angle. With 5.5 inches of lift which I have your steering wheel should still return to straight so I wouldnt worry about castor, just get that pinion angle correct and you should be good to go.

[XJ858]

Thanks for the links, I have those book marked now too. Ok I think Im going to just shoot for those target numbers myself and then try to find an alignment shop that can double check my work.