If you have a 3" or 4" lift. What caster do you have?

I have the RC 4" lift. With this kit, I have the stock front lower arms, and the maximum of caster I can get is 3.2 degree. In the RC instructions, the caster should be adjusted at 4.6 degree. But I can't
The technical support of RC told me that I can have 4.6 degree with my stock lower arms...
My caster has been inspected by 2 alignment shops in the last week, and the stock lower arms are too short of about 3/8"
Once again, the technical support of RC told me that I can have 4.6 degree with my stock lower arms...

 

I have about 6.5 degrees, I can basically adjust it to any degree I want.

 

from the factory, you should have +4.2° of caster. once lifted to 3"-4", i personally would recommend that you run something closer to +6° if you can. the best way to add more postive caster is with a set of adjustable front control arms. if you just get a set of lowers, set them to 23" eye to eye and that'll give you what you want.

 

Well you said you have the stock lower CA's, but not sure if you have new adj uppers?

Stock CA's and stock height have a "standard/factory" caster of 4.2 plus or minus .5 (if I remember correctly). So that means you can be at 4.7 and still be in factory spec. Well, now that your axle hangs lower (or your frame/body is lifted higher) AND you control arms are the same... your axle to rotates forward and lowers your caster.

Without adjustable CA's, there is no way at all to adjust your caster... much like there is no adjustment for camber either. In fact the ONLY alignment related adjustment that can be made on a stock JK is the toe-in/out. So, if you were stock, and your caster was not within the above spec, then something is broken or bent.

Ok, back to your issue... once you have larger/heavier tires and wheels, you want even more caster than stock. So, now this "max" caster of 4.7 become higher. The "correct" caster is debatable, but it seems 6+ is a good target with 35's (your sig doesnt say what size tire).

When you go to an ordinary alignment shop, they pull up your vehicle specs in their computer (which is usually hooked right up to the diagnostic machine). They might say you are "good" with 4.7* but it is impossible to achieve this with stock CA's and a 3-4" lift... here again, unless something is borken or bent. The exception to this is by using cam bolts, which is not very common.

So...... If RC is telling you that you can have 4.6* (which is the max factory spec) with their lift and stock CA's then something is not right. It is impossible to achieve without adjusting something more than the angle of your CA's with the lift. Furthermore, you now want to go even further than the 4.6 or so... I am not at all surprised that the max you can get is 3.2*.

You didnt mention adj upper CA's, but those have a tendency to be too long even when adjusted all the way to their shortest position. Maybe this is what you meant by only being able to adjust to 3.2*...

The bottom line is that you need to get adj lower CA's to rotate your axle to achieve more caster... Or live with shopping cart wheels as your front wheels....

 

Sheesh, that whole dissertation of mine and WOL beats me to it and in a much simpler way...

 

at least we were both on the same page

you can place it across the top of the ball joint or along the base of the knuckle. the ball joint is a bit harder to read but is the most accurate. if you place it along the base of the knuckle, you need to make sure that it sits flat across and not influenced by the shape of it.

 

Skip the angle finder, and pull out the tape measure. from the center of each bolt measure 23" like WOL. said. Only do this if you have adj. lowers only. with my teraflex kit, they suggested making the passenger side a tiny bit longer than the left. I can't remember if it was 1/8 or 1/16, but it made a world of difference. The jeep used to pull to the right during braking. I didn't think it was that bad until I noticed I was preparing to fight the pull under heavy braking... and the pull to the right never happened. Those teraflex guys know their sh!t!!! If you don't have adj. lowers in the front I def. recommend theirs!

 

Right. The tape measure is the best bet without an alignment machine.

Also, a point that no one has brought up yet in all of these lift/alignment threads......Caster angle is decreased two fold. 1) As the front axle drops down to lift the Jeep, it travels in an arc. That direction of travel causes the upper ball joint to pivot forward and the lower to pivot rearward, thus reducing caster. 2) At the same time, as the rear is lifted, it causes the same reaction to the front caster angle. As the rear comes up, caster is decreased even further. This is the reason that lifts affect caster so much. Caster is lost two different ways.

 

This is all very valuable info, but what if you have adj uppers and adj lowers? It says get the adjustment to 23" for lowers only, what if you have both?

23" for lowers and ?? for the uppers?

My caster was set at an alignment shop to 3.5 and 4.2 (I think), using adj CAs, but I still feel I should go a little higher and if I get under there and start working on it, I'd like to have an idea as to what effects it will have.

 

I have my FT uppers 1/8" shorter than stock and my FT lowers 3/8" longer and caster measures 7.1 on each side.
It drives beautifully and the JE Reel 1310HD (yokes) front driveshaft is smoother than stock. I think David suggested to me that the 1310 & yokes was the potentially smoothest aftermarket front driveshaft setup.

There is barely adequate clearance between the FT front trackbar and the ARB differential cover, but they have never touched.

With my mild lift (OME HD/3/4 spacer) I haven't had bumpsteer issues at all, but the Jeep can be just a little squirrely in the 45-60mph range over broken pavement & bumps, which of course is a characteristic of the short wheel base and the solid front axle. Tire pressure is a factor here as well. More at 29lb, almost none at 26. Have thought about increasing toe in just a bit but it drives so nice and tire wear is perfect so I haven't bothered.