Eddie, when you say 23" eye to eye, is that measuring from the center of the two eye holes that you pass the bolt through??? or a different area?

 

You are correct sir, center hole-center hole, or center of eye to eye of the control arm.

 

Oh no, that's not what I meant to say at all. Using "Both" is less of a compromise. As you increase the length of both arms, you need less of a pinion angle so you gain more caster.

It's like pointing to the top of a mountain. When you stand next to it you're pointing straight up. That would be your pinion angle. As you move away from the mountain the angle of your arm moves down.

Man I hope that makes sense.

 

You are right, although the amount you can move the axle forward is negligible in terms of the subtended angle, but I guess every little bit counts.

BTW, I think your analogy is more applicable to the high pinion design of the differential.

 

You pick
1)Perfect caster - poor pinion angle
2)Perfect pinion angle - poor caster
3)A compromise between the two.

Everyone one this board pretty much goes for (3).

My teraflex 6" long arm is a huge lift, more like 8 inches. For this reason I am running 1.5 degrees of caster. I am going to increase the caster to 3 degrees next week.

Personally id like my caster to be somewhere around 6 degrees I think.....

 

I'm glad this came up, so I didn't have to create a new thread for my research. Can any of you tell me the factory pinion and caster angles? I'm trying to figure out if I will need to turn the knuckles on a transplant.

 

Option 3 is the best option. Even the factory chooses this option.

If you are really concerned with Caster you are better of with a driveshaft with U-joints on both ends so the angle between the pinion and driveshaft doesn't have to be close to 0. In this case the constraint is that the driveshaft angle at both ends (transfer case and differential) should be the same so that both U-joints rotate at the same velocity which eliminates the main cause of driveshaft vibration.

 

Check the FAQ that WOL made a sticky at the beginning of the modified jk tech forum, it gives you the factory caster angles. I think it is something like 5.5 degrees and WOL suggests 6 to 8 degrees for 2 to 4 inches of lift. I have heard of VERY few people cut and turning knuckles in this thread so I do not believe it is absolutely neccessary. Just get nice new driveshafts, find a compromise you are happy with and enjoy your jeep.

 

Brandi let me say first of all your my kind of girl. OK... you did not mention if you were talking about the front or rear drive shaft. I think most of the post here assumed you were talking front because you were concerned with caster.

Rear drive shaft....don't worry about caster adjust the rear end so the u-joint, by the rear differential, bearings are doing the least amount of rotating i.e. no angle difference between driveshaft and pinion. (as in the illustration on the first page). The only thing an excess of caster does is make the rear springs bow and you need to make the end of each spring is positioned in the same place on the axle or one side of the jeep will sag more.

Front drive shaft.....adjust caster 4-6 degree range, this will not line up the driveshaft causing the u-joint to work more BUT in 2 wheel drive there is no torque on the drive line so it will last a lot longer in this position than the rear one would. As previously stated this is a compromise, the more caster you have the more it messes with the steering geometry.

Now that you know where to position the axle just adjust the CAs to make it happen. Extending Lower arms rotates the pinion down, shorting rotates it up.
Extending upper control arms rotates the pinion up, shorting rotates it down.

 

Thanks to everyone for your input, it helps a lot. I will shorten my LCA'S and order the new drive shaft.