sundevil

So before I had 3 inches of lift in the front, lower control arms set to 23 inches, uppers set to 18.75 inches and my caster was at a 4 degrees positive.

I have then added .75 inches of front coil spacer and swapped my upper control arms to the adjustable kind which can only shorten to 19 inches. What length should I set my front lower control arms to to get around ~4 caster?

I was thinking of using proportions but since I have moved two legs of the triangle I am unsure what to do.

From what I understand adding the coil spacers reduced my caster and then adding the slightly longer upper control arms also reduced my caster. I put an angle finder on the yoke which read -1 and then put it on the front drive shaft which gave me a -6 degree reading which means -5 degrees difference.
Been playing with 23, 23.25, 23.5 23.75 inches and I am honestly sick of installing and reinstalling these arms.
Haven't got any vibrations yet with any of those settings for the lowers.
Thanks

Biginboca

I would try 23.25" if you are running an aftermarket D.C. Driveshaft. 4* of castor sounds good but as you approach 4" lift some jeeps can't run that much castor on a factory housing without vibrations.

If you have a factory Driveshaft I would try 23.5" since you can get away with more castor without vibes. Of course you may have to reduce castor if/when your Driveshaft dies and you replace it with an aftermarket double cardan driveshaft.

resharp001

LOL, I know this feeling.

Typically you use the lower arms to set the axle position, and the upper arms to adjust the caster. Are you suggesting that your upper arms, even at the shortest they can be set, won't allow you to achieve 4* caster with the lowers set where you want? If that is the case, the uppers are as short as they get and you just increase the length of the lowers until you measure 2* at the pinion flange (the pinion is raised 2* from parallel to the ground). Keep in mind that if you're on a garage floor to account for any slope the garage slab might have. Could be minimal, but .5 or 1* needs to be accounted for.

The thing about measurements is that every jeep is different due to added weight or lack of which influences actual lift height. It's definitely not an exact science. Even manufacturer provided measurements are just a starting point and not a hard and fast "set it to this and you're perfect".

Trail Jeeps

Yeah, this is definitely one of those times when everyone's Jeep is slightly different. A number that worked on "my" Jeep might not work as well on "your" Jeep.

I agree with every statement made on this thread so far, but I would add that a good philosophy with this sort of thing is to eyeball it to a place where it drives well and gets along with your driveshaft, then I would take it to an alignment shop and get them to get it dialed in perfectly. Then you have real numbers to compare to yours. If you have to make adjustments from there, you'll be able to track your changes with more precision.

Everyone wants to be a driveway hero (myself included), but I always recommend getting it on a rack, at least once, after making any ride height changes. That way there is no guesswork.

sundevil

Thanks the replies guys I am making progress lol

I am running Adams Driveshaft's front and rear. I'll get my caster situated before I touch my toe with the 35s.

sundevil

New alignment specs any recommendations

Adams front
Teraflex 2.5 inch coil with .75 spacer
315/r17

Thanks

resharp001

You might be making this harder than it needs to be. Did your Adams DS mate up to the factory pinion flange, or did it replace that with a new yoke? If it is the factory flange it is easy to set an angle finder on. If it is a replacement yoke, you need to determine an accurate place to place the angle finder.

Since you know what the computer says your caster is, I would start by putting your angle finder on your pinion flange and read what it says, that way you have a basis for comparison and should be able to get it close. Computer says your caster is ~2*, so if you put your angle finder on the pinion flange you should see a reading of ~4*. I presume you understand the caster/pinion relationship, but just in case, or for others researching this thread, reference this picture -



Your axle has 6* of caster built in. That means that when your pinion is at 0*, caster is at 6*. For every degree that your pinion raises upward, your caster is decreased by that amount. Since the printout shows you have ~2* caster on the last scan, your pinion is raised by ~4*. Ideally you want to get that pinion at a 1-2* angle, which would put your caster at 4-5*. On a stock jeep it is 4.2*.

I presume your upper arms are as short as you can make them. I asked earlier in the thread but you didn't answer. If that is the case, your only option is to lengthen the lower arms which will push the axle forward while lowering the pinion. I didn't see you mention which control arms you have, but you should just be able to drop the appropriate side of the arm, adjust, reinstall, repeat on other side, and then remeasure your pinion. Since you don't have to remove tires or anything, this should only take a few minutes to accomplish. In a perfect world you would set the lower arms where you want the axle positioned, and then just use the upper arms to adjust the pinion. Since your uppers can only be set so short, you are a bit limited in how much they can adjust the pinion.

Unless you're just completely anal about things like this, don't worry if your caster reading is off just a tad from driver to passenger side. If the jeep isn't wandering it's not a big deal. You can only get things so close when your only options are adjusting by half turn increments on the control arm.