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-   -   Jeep Jk, Caster and lifting. (http://www.wranglerforum.com/f202/jeep-jk-caster-and-lifting-502001.html)

kjeeper10 01-25-2014 09:53 PM

Jeep Jk, Caster and lifting.
 
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**

http://i1031.photobucket.com/albums/...ps0oevy6hn.jpg

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.
http://i1031.photobucket.com/albums/...pspetbvt32.jpg

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

http://i1031.photobucket.com/albums/...psu5pp5b0j.jpg

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)

http://i1031.photobucket.com/albums/...pstkkebdqf.jpg

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, Tarafkex or I believe Curries front housings all have increased caster. Prorock unlimited being around 10*

As many know I'm running Rancho's drop brackets at about 3.5" of lift. Either circle reads around 1.5 which should have caster around 4.5.
I am running a aftermarket DS. Anything over 5* vibrates slightly. Eventually I want to add uppers and lowers. My thoughts are .. Moving the axle forward a bit will allow a little more caster. Hell .. I might try running both arms and brackets :hide:

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

Burke1973 01-25-2014 11:16 PM

1 Attachment(s)
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!

kjeeper10 01-25-2014 11:23 PM

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 ?

kjeeper10 01-25-2014 11:26 PM

Fwiw .. Your toe looks ok
Camber is a little high but under 1*
How many miles ? Bad ball joints can throw off camber.

Burke1973 01-25-2014 11:39 PM

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??

kjeeper10 01-25-2014 11:47 PM

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

Burke1973 01-25-2014 11:52 PM

Will do, thanks for the info!

This is why I love WF :thumb:

kjeeper10 01-26-2014 12:04 AM

:thumb:

JerryJeepster 01-26-2014 12:26 AM

I like running my Duratracs @ 28psi cold. They and I seem to like it a lot. Any higher psi and they want to wander quite a bit.

spinlock 01-26-2014 04:14 AM

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.

kjeeper10 01-26-2014 07:44 AM

Morning y'all. Thanks sir ^

JTPhoto JK 01-26-2014 10:44 AM

Quote:

Originally Posted by spinlock (Post 7731353)
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.


Agreed^^^ Thanks Ken.

Old Dogger 01-26-2014 12:47 PM

This is a excellent Thread demonstration, of caster, and the effect that it has on your pinion and drive shaft joint working angle.........:awesome:

kjeeper10 01-26-2014 01:02 PM

Quote:

Originally Posted by Old Dogger (Post 7738401)
This is a excellent Thread demonstration, of caster, and the effect that it has on your pinion and drive shaft joint working angle.........:awesome:

Spent a good amount of time on this, glad it helps :)

brighton 01-26-2014 05:10 PM

I'm always learning, and this is an excellent resource on caster and pinion angles. Thanks for posting this, kjeeper. This should be a sticky.

kjeeper10 01-26-2014 05:47 PM

Quote:

Originally Posted by brighton (Post 7743713)
I'm always learning, and this is an excellent resource on caster and pinion angles. Thanks for posting this, kjeeper. This should be a sticky.

Ty...I'll get it in our new reference thread. Prob is a lot of people use their phones and sticky's are missed. Either that or not read through :P

Seeuoffroad 01-26-2014 06:40 PM

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.

kjeeper10 01-26-2014 07:03 PM

1 Attachment(s)
Quote:

Originally Posted by Seeuoffroad (Post 7746265)
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 ..

Seeuoffroad 01-26-2014 07:20 PM

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.

kjeeper10 01-26-2014 07:25 PM

Quote:

Originally Posted by Seeuoffroad (Post 7747857)
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 ?

Seeuoffroad 01-26-2014 07:32 PM

I am going RCV's I'll have to be easy on the pedal so I don't tear up the R&P. But I have been wheeling with a D30 locked for two years and had zero issues with it.

Seeuoffroad 01-26-2014 07:38 PM

Quote:

Originally Posted by kjeeper10 (Post 7748081)
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 ?

So the synergy front track bar frame brace will work with my teraflex monster track bar?

kjeeper10 01-26-2014 07:42 PM

Quote:

Originally Posted by Seeuoffroad (Post 7748641)
So the synergy front track bar frame brace will work with my teraflex monster track bar?

I would call and make sure but I'm 99% sure it will.

LV Naturist 01-30-2014 12:05 PM

Thanks for the write up! I'm still researching how I want to lift my Jeep and have 1 question. You (and others) have talked about LCA brackets. Using these brackets will change the position of the LCA in relationship to the UCA in that they will no longer be (mostly?) parallel. Does this have any effect on the suspension performance or steering? Also, an adjustable LCA will keep the CA's parallel, but effects (forgot the proper term) instant(?) center? I'm only looking at a 2.5 lift... What issue should I be more concerned about to keep everything working properly? Hope you understand what I'm trying to ask.

John

kjeeper10 01-30-2014 12:23 PM

The brackets do a few things, change the operating angle of both upper and lower arms making them more parallel to the ground. This smooths out the ride over bumps.
Change instant center for less brake dive. Lastly the upper arm hole is set back to rotate the axle down for caster. Caster is what tightens the overall steering feel.
Adjustable mid arms only set wheelbase and pinion/caster, But if you are not relocating the mounts -like with a long arm. the geometry doesn't change. Even with adjustable mid arms.
That's where the brackets shine. Clearance is the only negative. Something to consider if rock crawling where clearance needed.

Specwar 01-30-2014 12:49 PM

Very informative, wish i would have found it before going through my issues.
Ended up installing just the front adjustable LCA, and ended with 4.8 positive on the drivers side and 4.9 on the passengers side. Sure cured the wandering issue i was having on my '08 JK with a 4" lift and 35's.
Was chasing a steering wobble ( DW if you wish) and also installed an adjustable track arm, with all the correct sized hardware.
Now the 35" Nittos stay on the ground :)

My caster was in the 2.something positive before the LCA's.

LV Naturist 01-30-2014 01:00 PM

Quote:

Originally Posted by kjeeper10 (Post 7852577)
The brackets do a few things, change the operating angle of both upper and lower arms making them more parallel to the ground. This smooths out the ride over bumps.
Change instant center for less brake dive. Lastly the upper arm hole is set back to rotate the axle down for caster. Caster is what tightens the overall steering feel.
Adjustable mid arms only set wheelbase and pinion/caster, But if you are not relocating the mounts -like with a long arm. the geometry doesn't change. Even with adjustable mid arms.
That's where the brackets shine. Clearance is the only negative. Something to consider if rock crawling where clearance needed.

Oh, okay... I was under the impression the brackets only changed the location of the lowers. It changes both? Thanks...

John

kjeeper10 01-30-2014 01:36 PM

1 Attachment(s)
Oh ... Sorry. Yes both

enjerhoo 01-31-2014 12:03 PM

Quote:

Originally Posted by spinlock (Post 7731353)
Great writeup Ken!

As always.

MAG00 02-03-2014 12:50 PM

I put a RockKrawler 2.5 Max Travel System lift onto my '13 JKU this weekend. It's off to the shop for an alignment now. They just called and like many have mentioned on here, the guy brought up cam bolts. Based upon my reading, I told him no on the cam bolts. He said that my castor on one side was just a hair over 5 and on the other was just a hair under 6. I told him I would like a print out and to just get it as close as he can and to not put cam bolts on.

For reference, here are some pics of when I checked it myself after the lift. First pic is of the angle finder sitting on my garage floor to account for any slope in the floor. Second pic is to show where I placed the angle finder. Third pic is the reading of the angle finder.

The front LCAs are turned in (screwed in) just about as far they can go. You might be able to get one full turn out of them...maybe.

What are ya'lls thought on the alignment shop comments and castor as well as how I checked it. I'll post the print out from the shop when I get it.

I drove some and it seem to drive fine although I haven't gotten it on the interstate yet. Only got up to about 50 mph on in town road.
Attached Thumbnails http://www.wranglerforum.com/attachm...1&d=1391445604 http://www.wranglerforum.com/attachm...1&d=1391445604

http://www.wranglerforum.com/attachm...1&d=1391445604


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