Front pinion/knuckle angle - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > General Technical Discussions > Advanced Jeep Tech > Front pinion/knuckle angle

Savvy FREE SHIPPING!Year End Clearance Sale! Save 20%Artec Holiday Sale!

Reply
Unread 01-13-2013, 01:11 PM   #1
cojab
Senior Member
 
cojab's Avatar
1993 YJ Wrangler 
 
Join Date: Oct 2010
Location: , Colorado
Posts: 920
Front pinion/knuckle angle

I am getting ready to rebuild with gears, locker, etc. a D30. I read a thread somewhere about setting the pinion angle correctly then setting the steering knuckle angle to correct castor. Can someone direct me to that thread or explain that relationship for me please.

cojab is offline   Reply With Quote Quick reply to this message
Unread 01-13-2013, 02:55 PM   #2
ratmonkey
R.I.P.
 
ratmonkey's Avatar
1997 ZJ 
 
Join Date: Dec 2006
Location: , Pennsylvania
Posts: 19,794
Only applies if you are cutting the c's off to rotate them. Otherwise your caster is what ever it is when you have the correct pinion angle.

Pinion angle takes first priority over caster.
__________________
'97 zj 5.2, some stuff, some other suff, and some things that even work sometimes.

ratmonkey is offline   Reply With Quote Quick reply to this message
Unread 01-13-2013, 06:55 PM   #3
cojab
Senior Member
 
cojab's Avatar
1993 YJ Wrangler 
 
Join Date: Oct 2010
Location: , Colorado
Posts: 920
Agreed, pinion over castor but why not correct any castor while diff is out. My understanding is this helps correct bumpsteer, right? (Along with ball joints, tires balanced, etc, etc.)
cojab is offline   Reply With Quote Quick reply to this message
Unread 01-13-2013, 08:29 PM   #4
ratmonkey
R.I.P.
 
ratmonkey's Avatar
1997 ZJ 
 
Join Date: Dec 2006
Location: , Pennsylvania
Posts: 19,794
Quote:
Originally Posted by cojab View Post
Agreed, pinion over castor but why not correct any castor while diff is out. My understanding is this helps correct bumpsteer, right? (Along with ball joints, tires balanced, etc, etc.)
why not? because rotating the knuckles is a TON of work and not really needed without extreme lifts or when using scout d44's(no rotation of the knuckle relative to the pinion at all in stock form)
__________________
'97 zj 5.2, some stuff, some other suff, and some things that even work sometimes.

ratmonkey is offline   Reply With Quote Quick reply to this message
Unread 01-14-2013, 10:04 AM   #5
slmason72
Member
 
slmason72's Avatar
2003 TJ Wrangler 
 
Join Date: Oct 2012
Location: Woodstock, Georgia
Posts: 241
Link to castor / pinion chart that another JF member directed me to a while back. Previous comments about pinion first apply, but you may have to compromise at some point and dial the pinion back. If you do, do so in small increments and check for vibrations.

http://go.jeep-xj.info/HowtoAlignment.htm
slmason72 is offline   Reply With Quote Quick reply to this message
Unread 01-14-2013, 11:00 AM   #6
Imped
Web Wheeler
 
Imped's Avatar
2004 TJ Wrangler 
 
Join Date: Feb 2008
Location: Indianapolis
Posts: 19,683
The whole "pinion over caster" thing is BS and certainly doesn't apply to all situations. Even with how low my rig is, the required pinion angle is still fairly high due to my flat belly. If I ran the pinion inline with the drive shaft, I'd be at about 3* caster with my HP30.....that little caster feels like ****. I run the pinion a few degrees low and run 6* of caster. Steering is great and I've got no driveline vibes.
__________________
OlllllllO
Float Test Build
IndyORV
Imped is offline   Reply With Quote Quick reply to this message
Unread 01-14-2013, 11:12 AM   #7
ratmonkey
R.I.P.
 
ratmonkey's Avatar
1997 ZJ 
 
Join Date: Dec 2006
Location: , Pennsylvania
Posts: 19,794
Caster depends fully on tire size.
Larger tires will give the same trail numbers that result in good handling with much lower caster angles.
3-4 should be nearly perfect for a 37", I'd expect 6 to be excessive.

I ran 4 on 35's and will have roughly the same on 37's. It returned to center well and didn't go crazy following the crown.
__________________
'97 zj 5.2, some stuff, some other suff, and some things that even work sometimes.

ratmonkey is offline   Reply With Quote Quick reply to this message
Unread 01-14-2013, 11:59 AM   #8
Imped
Web Wheeler
 
Imped's Avatar
2004 TJ Wrangler 
 
Join Date: Feb 2008
Location: Indianapolis
Posts: 19,683
3* felt like crap to me on 37's, 6* feels excellent. I'm sure 5* would be fine as well but I wouldn't want to run less than that. I know that, on paper, larger tires requiring less caster to give the same results makes perfect sense. But I've not found that to translate well to actual use.
__________________
OlllllllO
Float Test Build
IndyORV
Imped is offline   Reply With Quote Quick reply to this message
Unread 01-14-2013, 01:03 PM   #9
slmason72
Member
 
slmason72's Avatar
2003 TJ Wrangler 
 
Join Date: Oct 2012
Location: Woodstock, Georgia
Posts: 241
I started we'll under 3, ended up at 5.5 degrees. Wish I had started with castor angle and worked backward to a pinion angle that produced no vibes. Would have saved me several adjustments.
slmason72 is offline   Reply With Quote Quick reply to this message
Unread 01-14-2013, 01:08 PM   #10
ratmonkey
R.I.P.
 
ratmonkey's Avatar
1997 ZJ 
 
Join Date: Dec 2006
Location: , Pennsylvania
Posts: 19,794
I've found that tire width and wheel offset has a lot more to do with steering feel than caster.
__________________
'97 zj 5.2, some stuff, some other suff, and some things that even work sometimes.

ratmonkey is offline   Reply With Quote Quick reply to this message
Unread 01-15-2013, 03:38 PM   #11
cojab
Senior Member
 
cojab's Avatar
1993 YJ Wrangler 
 
Join Date: Oct 2010
Location: , Colorado
Posts: 920
Thanks slmason. I believe thats what I'm looking for. I am changing gears and will have an extra diff out of the jeep building it while I'm still driving my current set up. I guess my whole thinking behind this question is will I need to change the spring perch locations on the front like I am on the back and I wasnt sure if I needed to rotate the knuckles when I did this or not.
Thanks for the replies
cojab is offline   Reply With Quote Quick reply to this message
Unread 01-18-2013, 09:18 PM   #12
AdvRacer
Registered User
2000 XJ Cherokee 
 
Join Date: Sep 2012
Location: Iowa Falls, IA
Posts: 15
Here is an excellent write up on cutting and turning the c's ( along with a lot of other things )

http://www.naxja.org/forum/showthrea...=913774&page=9
AdvRacer is offline   Reply With Quote Quick reply to this message
Unread 01-21-2013, 07:09 AM   #13
SLADE
Registered User
2004 TJ Wrangler 
 
Join Date: Jul 2010
Location: 26537
Posts: 1,993
Quote:
Originally Posted by ratmonkey View Post
Pinion angle takes first priority over caster.

Quote:
Originally Posted by cojab View Post
Agreed, pinion over castor
BS

This is not true and very missleading.

A proper pinion angle will be of absolutly no use if you can't keep the jeep on the road because of a lack of caster.

You have to find a happy medium between the 2. You should not set one without taking the other into consideration.

It is better to set the caster and then rotate just enough to eliminate driveshaft vibration and binding.
__________________
2014 Wrangler JKU
2013 Wrangler JK
2004 Wrangler TJ on LEAFS
2001 Dodge Ram 2500
SLADE is online now   Reply With Quote Quick reply to this message
Unread 01-21-2013, 03:10 PM   #14
JeeperDon
Patience, Grasshopper
 
JeeperDon's Avatar
1993 YJ Wrangler 
 
Join Date: Jan 2005
Location: Albuquerque, NM
Posts: 6,645
Quote:
Originally Posted by ratmonkey View Post
Caster depends fully on tire size.
Larger tires will give the same trail numbers that result in good handling with much lower caster angles. 3-4 should be nearly perfect for a 37", I'd expect 6 to be excessive.
If you do the math, which I'll leave out here...
The center point of the spec range for caster for my '93 YJ is 6.3.
1) Assuming that is for the stock 29" OEM tires, that puts the tire's ground contact point 1.6" in front of the axle.
2) A 35" tire needs 5.3 to put the contact point in the same place.
3) A 37" tire needs 5.0 to put the contact point in the same place.

I know my YJ with 35's is all over the road with the caster at 3.3. I plan on moving the perches to fix it soon.
__________________
'93 YJ, '02 GM 4.3 Vortec V6, SOA, dual ARB's, 8.8+D30(w/WarnHubs), 4.88 gears, 35" BFG KM2's, AX15, 15x7 wheels, NP231+4:1+SYE+2LO, York OBA, Warn M8000, no top or doors Apr-Oct.
Member and Web guy: New Mexico 4 Wheelers My Truck Page on NM4W Site
JeeperDon is offline   Reply With Quote Quick reply to this message
Unread 01-28-2013, 08:08 AM   #15
cojab
Senior Member
 
cojab's Avatar
1993 YJ Wrangler 
 
Join Date: Oct 2010
Location: , Colorado
Posts: 920
OK, after doing a bit more reading on this let me see if my plan seems right to you guys in the know. First off I'm not running an extreme amount of lift so I'm not sure I am going to "need" to turn the C's at all but if I do this axle I only want to do it once so I will probably go ahead and get it as close as possible. Right now I'm on 33's with a total of 4" of lift but I might go up to 35's at some point so I figure it will be a little more needed then, and I should be very close if I do this now.
1. Strip spring perches and shock mounts.
2. Figure correct pinion angle
3. Cut out and set C's at about 5.5-6.0 degrees
4. Trial fit, adjust, and weld up if good.
Does this sound right or like overkill? Also does anything change if I decide to upgrade to TJ axles with this. My D30 is 27 spline right now. Are the TJ axles also 27 spline or different?
@JeeperDon- if you just move your perches to set castor are you planning anything for pinion DS/angle or just prioritizing castor over pinion. Mine is a semi DD so I really prefer both. I also dont want any shims in when I am done with this.
cojab is offline   Reply With Quote Quick reply to this message
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.
Note: All free e-mails have been banned due to mis-use. (Yahoo, Gmail, Hotmail, etc.)
Don't have a non-free e-mail address? Click here for a solution: Manual Account Creation
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.


Thread Tools






Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.