Keeping the front end "down"/hill climbs/Instant Center... - Page 8 - 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 > Keeping the front end "down"/hill climbs/Instant Center...

ANOTHER Rockridge4wd Creation!! Spare Tire Carrier Delete ROCKRIDGE4WD Introduces a NEW Jeep Wrangler JK *led* tail Engo winches available at www.rockridge4wd.com! Free shipp

Reply
Unread 12-23-2011, 09:02 PM   #106
mrblaine
Wizard of Brakes
 
mrblaine's Avatar
1999 TJ Wrangler 
 
Join Date: Dec 2004
Location: Quail Valley, California
Posts: 26,367
Quote:
Originally Posted by ftgiles View Post
Pretty sure he means "twist" not wrap.

The length of the arms and their pivot point relationship causes the axle to either twist or not. You want the front axle to twist as it moves through the arc of the control arms because that maintains a constant caster angle.
In case folks don't understand the importance of that for some rigs, when you build custom steering, trackbar, blah blah blah, real estate for places to get mounted and live becomes very precious. Sometimes the tolerances are less than 1/8" between moving parts. If you get any or a lot of caster change, the tilt of the axle as it moves through the range of motion can cause stuff to crash into each other.

The down side is you wind up with a parallel 4 link or equivalent which isn't always the best geometry, but it preserves the close tolerances. Another downside is the pinion angle doesn't change, so it can run the pinion yoke into the rocks at full articulation driver's side down if you don't pay attention.

__________________
I am Savvy
blackmagicbrakes.com
mrblaine is offline   Reply With Quote Quick reply to this message
Unread 12-25-2011, 10:58 PM   #107
Hussler
Registered User
1992 XJ Cherokee 
 
Join Date: Jan 2009
Location: utica, new york
Posts: 5,287
Quote:
Originally Posted by ftgiles View Post
Pretty sure he means "twist" not wrap.

The length of the arms and their pivot point relationship causes the axle to either twist or not. You want the front axle to twist as it moves through the arc of the control arms because that maintains a constant caster angle. Or maybe in the rear you don't want a twist so that you maintain a constant pinion angle.
No, wrap. By making the lower link in line with the axles centerpoint I was thinking it would make the axle would lose some of its ability to hold proper caster under load. Like, it would want to rotate forward.
Enlighten me please.
__________________
Quote:
Originally Posted by chris87xj View Post
Sometimes a restoration project is a labor of love, at which point cost, time, and labor involved become irrelevant.
Quote:
Originally Posted by BorderC View Post
I see you also twizzled your scart lead. Well done! :thumbsup:
92 XJ with ARB's, 5" lift, too much armor, 33's and some other garbage
Hussler is offline   Reply With Quote Quick reply to this message
Unread 12-26-2011, 01:10 AM   #108
ftgiles
Registered User
 
Join Date: Jun 2008
Location: Phoenix, AZ
Posts: 1,643
Quote:
Originally Posted by Hussler View Post
No, wrap. By making the lower link in line with the axles centerpoint I was thinking it would make the axle would lose some of its ability to hold proper caster under load. Like, it would want to rotate forward.
Enlighten me please.
You're right. If you decrease the separation of the ca's on the axle, then there is less leverage available to control wrap. Less separation requires bigger joints and stronger mounts. More separation allows you to run smaller components.
ftgiles is offline   Reply With Quote Quick reply to this message
Unread 12-27-2011, 10:45 AM   #109
Imped
Web Wheeler
 
Imped's Avatar
2004 TJ Wrangler 
 
Join Date: Feb 2008
Location: Indianapolis
Posts: 19,523
I run 8" of vertical separation at the axle with 2.5" JJ's all around. Again, zero movement. The axle can't roll one way or the other because the control arms won't let it.
__________________
OlllllllO
Float Test Build
IndyORV
Imped is online now   Reply With Quote Quick reply to this message
Unread 12-27-2011, 07:37 PM   #110
Hussler
Registered User
1992 XJ Cherokee 
 
Join Date: Jan 2009
Location: utica, new york
Posts: 5,287
Quote:
Originally Posted by Imped View Post
I run 8" of vertical separation at the axle with 2.5" JJ's all around. Again, zero movement. The axle can't roll one way or the other because the control arms won't let it.
I was looking at your truss, did you move your upper control arm mounts higher than stock to make up for separation? Did you move the upper control arm mounts (axle end) towards the rear of the jeep?
__________________
Quote:
Originally Posted by chris87xj View Post
Sometimes a restoration project is a labor of love, at which point cost, time, and labor involved become irrelevant.
Quote:
Originally Posted by BorderC View Post
I see you also twizzled your scart lead. Well done! :thumbsup:
92 XJ with ARB's, 5" lift, too much armor, 33's and some other garbage
Hussler is offline   Reply With Quote Quick reply to this message
Unread 12-27-2011, 09:51 PM   #111
Imped
Web Wheeler
 
Imped's Avatar
2004 TJ Wrangler 
 
Join Date: Feb 2008
Location: Indianapolis
Posts: 19,523
Quote:
Originally Posted by Hussler View Post
I was looking at your truss, did you move your upper control arm mounts higher than stock to make up for separation? Did you move the upper control arm mounts (axle end) towards the rear of the jeep?
Yes, they are higher than stock. The only way to get them as low as stock (or even close) is to not run them on top of a truss (above the diff). You'd have to run them beside the diff.....just like stock. All else being equal, if I ran them that way my AS would be very low (unless I moved the joint at the frame upper mount down) and the separation would be pathetic....like 6" and 4". And yes, they are moved back. You need to remember that my pinion is quite a bit higher than stock, which rolls the upper mounts back. No, it really doesn't matter at all.
__________________
OlllllllO
Float Test Build
IndyORV
Imped is online now   Reply With Quote Quick reply to this message
Unread 01-03-2012, 06:52 PM   #112
RaggedOleMan
Registered User
2005 TJ Wrangler 
 
Join Date: Jul 2007
Location: , Sane's Ville
Posts: 2,340


(Image above is with the 1-1/4" pucks removed)



(Image above includes the 1-1/4" pucks)

I modified the top illustration to reflect the removal of the 1-1/4" pucks, leaving the OME 2-1/2" + 1/4" spring isolators. The numbers that result are better, though far from the ideal, as I understand it.

If I use IMPED's cog, the results improve slightly, in my case. The Anti Squat numbers in the image that are associated with IMPED's COG are in "blue" and are = to 242% as opposed to the 251% with the pucks. If the ideal % is around 100%, then my set up is, for the sake of this discussion, friggin' horrible.

Seems to me that the stock control arm mount locations are only really suitable for stock tires and stock lift/height. Once lifted, in this case with the OME 2-1/2" lift, and 33" tires the end results bring on the suck...relative to IC and this discussion.

Am I beginning to understand this correctly?
RaggedOleMan is offline   Reply With Quote Quick reply to this message
Unread 01-03-2012, 09:05 PM   #113
ftgiles
Registered User
 
Join Date: Jun 2008
Location: Phoenix, AZ
Posts: 1,643
Quote:
Originally Posted by RaggedOleMan View Post

Seems to me that the stock control arm mount locations are only really suitable for stock tires and stock lift/height. Once lifted, in this case with the OME 2-1/2" lift, and 33" tires the end results bring on the suck...relative to IC and this discussion.
Two big red stars!!


But as you know, there is a lot more to it besides IC's. And the suck isn't really that bad for 2" of lift. The suck is really at 4" of lift and stock control arm frame mount locations.
ftgiles is offline   Reply With Quote Quick reply to this message
Unread 01-23-2012, 12:07 PM   #114
flip2spin
Registered User
2006 LJ Wrangler 
 
Join Date: Aug 2003
Location: Gatlinburg, Tennessee
Posts: 226
Quote:
Originally Posted by ftgiles View Post
Two big red stars!!


But as you know, there is a lot more to it besides IC's. And the suck isn't really that bad for 2" of lift. The suck is really at 4" of lift and stock control arm frame mount locations.
great thread
flip2spin is offline   Reply With Quote Quick reply to this message
Unread 01-29-2012, 12:54 PM   #115
Timido
Registered User
2003 TJ Wrangler 
 
Join Date: Feb 2011
Location: cin, oh
Posts: 183
Good reading. What is good for roll axis height for street trail Rig. Right now I have 85% Anti squat on the top hole and %105 on the middle hole with 2deg roll axis angle and 27" roll center height.

My 4link number links
http://farm8.staticflickr.com/7019/6...79e0b37a_b.jpg

http://farm8.staticflickr.com/7030/6...b6e530ed_b.jpg
Timido is offline   Reply With Quote Quick reply to this message
Unread 01-29-2012, 02:00 PM   #116
pcoplin
Web Wheeler
 
pcoplin's Avatar
1998 TJ Wrangler 
 
Join Date: Jun 2008
Location: Beaverton, OR
Posts: 1,805
In my (limited) experience, the flatter the roll axis the better. 2 degrees is good, and I would run at the 85% hole. Your lower triangulating is keeping that roll axis low. The farther out towards parallel you get the steeper it will become. But really, get out and drive/wheel it on both settings and go with whichever feels better.
__________________
98 TJ 5.9/46RE/D300
85 Wagoneer 5.2/44RE
01 F250 Powerstroke 7.3/ZF6
Ultra4 KOH #689 car
pcoplin is offline   Reply With Quote Quick reply to this message
Unread 04-10-2013, 01:22 AM   #117
aTX427
Registered User
1999 TJ Wrangler 
 
Join Date: Jul 2011
Location: Central, TX
Posts: 446
Found a decent read on instant center, roll center and roll steer.
http://www.sporttruck.com/techarticl...nt_center.html
aTX427 is offline   Reply With Quote Quick reply to this message
Unread 04-11-2013, 12:08 AM   #118
Kodiak17
Registered User
1998 TJ Wrangler 
 
Join Date: Sep 2010
Location: Kutztown, PA/ Andover, NJ
Posts: 3,725
Love this thread.
__________________
Maintain, wheel, upgrade, repeat.

My build: http://www.jeepforum.com/forum/f22/thor-dd-weekend-warrior-1348534/
Kodiak17 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


Suggested Threads





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.