King post angle

StG58

TJ Guru
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Oct 29, 2015
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Orygun, the wet side...
I'm looking to increase the tire size on the TJ to correct a couple of issues that I have run into recently. I would like to do a sanity check on what the decreased wheel back spacing is going to do to my scrub radius. Anyone have any ideas on what the king pin angle on the TJ is? It's cold out and I'm to lazy at the moment to crawl under the rig and take measurements. Thanks a bunch.
 
Kingpin angle is kind of an older term and I think you may be asking what the caster angle is. For stock size tires, it should be 7 degrees. But the larger the tire, the less caster angle that is needed. LIke 5-6 degrees is more appropriate if you're running a 35".
 
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Yeah you threw me off there with the "kingpin angle". I'd never heard that term before.
 
Ahhh, let's try this using different terms... I'm not a suspension guy, and it shows. But then, that's why I ask questions.

How about steering axis angle? The angle formed by the upper and lower bearings that the steering knuckle turns on. Feel free to correct any of this terminology, please.

The line from the steering axis angle and the centerline of the tire contact patch can give positive, negative or zero scrub radius. To much scrub radius can cause handling problems. To little seems to cause braking problems.

Need to think this through a little more, or just ask the basic question. 33x12.50's on a 15 x 8 rim with 3 1/2 inch back spacing. On a TJ. Will it work or is it a death trap. I'll try to understand it later.