Jeep Wrangler Forum banner

1 - 20 of 1521 Posts

·
Super Moderator
Joined
·
53,763 Posts
Discussion Starter #1 (Edited)
What is caster, how lifting has a effect on caster, How to read caster, and fixes.

**Caster is the tilting of the uppermost point of the steering axis either forward or backward (when viewed from the side of the vehicle). A backward tilt is positive (+) and a forward tilt is negative (-). Caster influences directional control of the steering but does not affect the tire wear and without adjustable control arms, is not adjustable on this vehicle. With too little positive caster, steering may be touchy at high speed and wheel return-to-center may be diminished when coming out of a turn**



The caster and pinion angles are set. Raising/lowering caster has the opposite affect on pinion, and vise versa.
Problem for some of us, the Jk only has 6* between these two angles. 4.2* caster and 1.8* pinion angle. At stock height the driveshaft is at a decent angle.
What happens when the Jk is lifted ? The higher the Jk is raised from stock height, the axle is rotated up , which actually betters your pinion/DS angle. Caster angle is decreased which might affect handling,
There's a few variables like height, size tire, type of driving, etc. A small drop in caster might not even bother you. If your jeep does not include (at min) front lower control arms or drop brackets. Plan on them if the jeep handles poorly.

If your kit does come with adjustable/fixed control arms. Obviously you will be able to tune to your liking. Most company's shoot for stock 4-4.5* but I've seen people (this includes me) try and run 6* with a modest lift. Your driveshaft won't like this trust me :nonono:

The issue with 4" of lift, there's not enough separation (6*) built into the axle to run a safe balance. Stock caster still might be too much for the driveshaft angle. Running a aftermarket double carden DS, it becomes more of hassle trying to balance the two angles to prevent vibes or TC failure. I've seen 3*/3* of in some cases 2* caster and 4* pinion. I could only imagine how the jeep drives :eek:

Some kits will supply cam bolts. Me personally, I don't care for them. The factory lower axle mount is opened up for a offset bolt which will give a small caster bump.


Then there's control arm drop brackets offered by Rancho, AEV, Rough Country, TNT customs. These provide a very nice ride, not only correcting caster but changing the geometry. These may not be for you on a trail rig where clearance is a concern.

How do you read your caster angle?
Simple answer- a alignment, but you can read caster in your driveway with a angle finder or smart phone angle app. Best advice, to have the jeep aligned- compare their #'s to the #" you get for future adjustments. Ex.. You wanted and set for 4* and the alignment reads 5*. Next time around set your caster to 3* knowing the 1* difference,
I set my lower CA's at the time for 4* and alignment read 4.5* (slaps myself on the back)
There's a couple ways to read caster around the interwebs that really is not accurate. Measuring of the lower C which is a cast surface. Another method is off the upper ball joint, I tried this with no luck.

The easiest and preferred method to read caster off the pinion flange. Ok... That doesn't make sense?? Actually it does. We know the JK has 6* between the two angles. Knowing what your pinion angle -- some simple math --will give you caster.
Here's a pic measuring off the pinion flange



Also the two flat circles on each side of the pumpkin can read pinion also. These 2 spots are perpendicular to the pinion flange (above)



Now take your measurement and total 6
Stock is going to read around +2* or (88*) caster = 4*
If the pinion reads +1* or (89*) caster = 5*
If the pinion reads. 0 caster = 6*


You might have read about people cutting and rotating the factory C's. A lot of fab and welding involved but a option to increase caster on the factory housing,

Aftermarket housings like The Prorock, Taraflexand I believe Curries front housings all have increased caster. Prorock unlimited being around 10*

Rockslide engineering now has a TC brace available. The brace was designed to keep the case in one piece if a driveshaft were to fail. Reasons: out of balance, worn centering ball, too much caster angle (front), not enough pinion angle rear), worn u-joint, etc



I'm leaving this open for any questions or opinions. Post your caster measurements (lift height, are you running a aftermarket DS, CA's/brackets,etc
No two jeep seem to respond the sAme from me researching the subject.y
 

·
Registered
Joined
·
181 Posts
So, I had a 2.5" Teraflex lift put on with some 315/70/17 Duratracs. Steering felt a little off so I figured to get an alignment done. After it was done the steering improved but still feels a bit loose. Thinking of adding a stabilizer to see if it helps. This was the report I received on the alignment. Anyone have any input as I am not too mechanically inclined!
 

Attachments

·
Super Moderator
Joined
·
53,763 Posts
Discussion Starter #3
Thanks for posting. Look at your final caster spec
Before or final because with the stock housing -caster is not adjustable. From my own experience, a 1* bump In caster will help a lot.
Yours is around 3* about 1-1.5 less then stock.

Do you wheel where clearance is a concern?
A set of drop brackets will really help handling and raise caster.

lower CA's. Adjustable or fixed. These will be longer/adjusted longer then stock,

Or adjustable uppers shorter than stock. These tend to be cheaper but a little harder to install/adjust,

You have a few options. Low caster will def cause some handling issues.
What's your tire psi ?
 

·
Registered
Joined
·
181 Posts
Happy to post and learn :thumb:

Tires are running at 34psi, clearance is not a great concern as of now, the wheeling down here in Va is mostly trails with some small rocks thrown in.

I am always looking to improve the ride as it is my DD, it has the rear drop bracket.

I just hit 6000 miles so many more years to come!!

I am wondering if they could have made the right camber and left toe in spec though??
 

·
Super Moderator
Joined
·
53,763 Posts
Discussion Starter #6
Toe is fine. Camber is not adjustable. If you have a chance. Get each tire off the ground about 3" and pry up from underneath. Ball joints are hard to miss if bad. You can see movement and possibly hear a noise.

I posted a thread on the Rancho drop brackets a few months back. Check em out.

Lastly chalk your tires. That's a 35" right ?
25-28 is typically good for a 35" tire
 

·
Registered
Joined
·
181 Posts
Will do, thanks for the info!

This is why I love WF :thumb:
 

·
Registered
Joined
·
5,701 Posts
Great writeup Ken!


Everyone that wants to lift their Jeep, particularly more than 3.0", should read this post so they can understand what they have to contend with.
 

·
Super Moderator
Joined
·
53,763 Posts

·
Registered
Joined
·
331 Posts
Kjeeper10 I am putting a Prorock 44 ultimate extreme with Reid knuckles with teraflex 4" lift 37 tires. Also synergy tie rod and synergy high steer flipped drag link. Am I missing anything or is there something I should be doing to get the best steering and handling possible.
 

·
Super Moderator
Joined
·
53,763 Posts
Discussion Starter #18
Kjeeper10 I am putting a Prorock 44 ultimate extreme with Reid knuckles with teraflex 4" lift 37 tires. Also synergy tie rod and synergy high steer flipped drag link. Am I missing anything or is there something I should be doing to get the best steering and handling possible.
I would add a upper frame brace. If the kit doesn't supply their track bar go Synergy with both. There's the optional sector shaft support too.

Not mine ..
 

Attachments

·
Registered
Joined
·
331 Posts
Thanks. Dynatrac is welding on brackets to the axle for my teraflex monster trac bar and drag link. The frame brace is something I was not familiar with. I'll look into it. Thanks again.
 

·
Super Moderator
Joined
·
53,763 Posts
Discussion Starter #20
Thanks. Dynatrac is welding on brackets to the axle for my teraflex monster trac bar and drag link. The frame brace is something I was not familiar with. I'll look into it. Thanks again.
Just be aware. You might be ok with the height, the large loop of the TF track bar can rub the pitman arm. Mine is close but haven't flexed it enough yet.
I think you only have to run Synergy's track bar when running the optional sector shaft brace. The frame bracket by itself is no problem and easily bolted on.

What a setup you're going to have going. You doing RCV's ?
 
1 - 20 of 1521 Posts
Top