Well, my north-ridge presents came today.

I got some lower control arms, that I'll be installing tomorrow. The problem is my driveway is at a slight incline, and it isn't flat at all (so I figured it's impossible to use a angle finder).


So I'm wondering how much I should extend the control arms to get the correct amount of castor???

 

Set em at 23" and test drive it.

 

If you like it, stay there, if not, increase by an 1/8" and re-test. With just the BB' you should be good at 23" though.

 

You can start with about 23" eye to eye for the front lowers. That should get you in the ballpark.

 

......

 

yup...23" got me to 5° on a 2.5" TF lift.

Here's an ongoing thread that will pretty much tell you the same thing ... Have 2.5" TF coil lift - what do adj trackbar/control arms do?

 

Almost certainly you can find a flat piece of concrete at some closed gas station, business, or something nearby. So after setting them to 23 drive over there and take a measurement.

Whether you should be shooting for some particular number or just a Jeep that drives good is up to you. When I first installed my upper FT control arms with the stock lowers I set them to 1/8" shorter than stock (the minimum setting) and the Jeep drove amazingly well.
This gave an angle finder number of about 5 degrees. Later, I installed the lower arms at roughly 1/4" longer than stock, giving a number of 7.1, but only a mild improvement in front end performance over the stock lowers/FT uppers combination.

One advantage of using both upper and lower arms is that you can maintain clearance between the differential cover and the trackbar, a factor that turns out to be important with some trackbars and diff covers.

How this "angle finder" caster number actually relates to the true caster number you would get on a computerized alignment machine is beyond me, but if you get a number in the 5-6 range you should be good.

We always get warnings about how too high a number might cause vibrations with a front aftermarket driveshaft, but my JE Reel 1350HD unit which uses replacement yokes on both ends has been smoother than the factory shaft.
There seems to be a great deal of variation in the production chassis so that some Jeeps are good with higher numbers and some are not. However, one particular Jeep Unlimited around here was having big problems with shaft vibration (Tom Woods 1350) at an angle finder setting of 4.6 with lower arms only. Uppers solved his trackbar-diff cover clearance issues AND the vibration issue with his angle finder caster number now at 6.8.

 

Maybe I'll go with a little less than 23", to account for the springs settling?


Then again, I'll probably have to re-adjust the track-bar brackets too, when that occurs, no???

 

I would recomend not guessing at this. The numbers mentioned here are correct, but if you guess wrong you could get the dreaded Death Wobble.

I agree that you should set and and find a flat spot to check, and be prepared at that point to adjust.

Just my 0.02

 

Go with 23" man and you'll be ok.