Author Topic: SOA or SUA  (Read 1756 times)

Offline Mr Rock

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SOA or SUA
« on: October 29, 2009, 12:20:09 AM »
I keep flipping back and forth on weather to install my new 4.10 axles SUA or SOA. I have D30 and a Ford 8.8 ready to go on my 4" RC springs. My goal is to run 35's with no body lift. Will I be too high SOA with the saggy 4" springs? I have already opened the rear wheel wells and installed TJ rear flares and plan on installing flat fenders up front.
What do you guy's think?
'89, 4.2, NUTTERED, Team Rush, 4" Lift, 1" BL, 1" MML & HD shackles , Flat Belly Skid, SYE, 36 x 13.50s
XRC8, 150w KC's, Herculined, Tauras Elec Fan, Dual Batteries, Aussie in front, 8.8, TJ flares & Spool in rear, topless all of the time!

Offline calvynandhobbs

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Re: SOA or SUA
« Reply #1 on: October 29, 2009, 12:31:36 AM »
My old CJ7 was SUA with 4" springs, a 1" body lift, TJ flares and 35s fit great with plenty of room in the wheel wells. Kirk is currently running spring under with a 4" lift and a 1" body lift with his 35s. If I remember right SOA is automatically 4" or 5" of lift if you used flat springs so with 4" lift springs you'd be looking at 8 or 9" and then you'll need 37s or 39s to fill the wheel wells. SUA is also much easier to put together than SOA. There is a lot of modifications when it comes to your steering and other things when you go SOA. Since you already cut your wheel wells out you should be fine running SUA and 35s. Here's an old pic of my CJ7.



1994 YJ on 37s

Offline kirksjeep

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Re: SOA or SUA
« Reply #2 on: October 29, 2009, 02:48:19 AM »
The old SOA vs. SUA debate.  There are a list of Pros and Cons for either way.  I debated the same thing when deciding on which way to go, and the biggest factor for me was stability.  SOA with flat springs typically flex better then arched springs, but anyone who has seen my Jeep in action will agree that my system flexes really well.  SOA opens a big can of worms with the steering and often the only safe way to do it is to do a complete custom steering set up, which can be pretty expensive and hard to find parts for if you bend/ brake something. 

Looking around at the GAJR I noticed the past two years that the majority of leaf sprung Jeeps were running SUA.  There is one section of a ledge at MaBell that according to a local has only ever been climbed by SUA Jeeps since coil springs are too bouncy and tend to cause roll overs, and another local with a TJ was proof with his smashed hood and windshield. 

I run 35's with 4.5" of suspension lift, a 1" body lift and still had to trim about 2" out of the rear fenders.  There are some really good advantages to the 1" body lift.  With the BL I was able to install a 1" Motor Mount Lift which angled the drive train to better align the drive shaft.  Also with the BL and MML I can do a belly up skid and gain 3.5-4" in the center of the Jeep which seemed to get hung up a lot back at BTC.  I can also raise the Gas tank skid 1" to gain some departure angle. 

Another thing to consider is that most SUA are designed my engineers and SOA are designed by back yard mechanics.  It's not that a back yard set up can't work well, but it usually takes a lot of trial and error.
1992 YJ Sahara, 4.5 Rubicon Express ED Lift, 35" BFG MT, Custom Bumpers, SYE/CV Drive Shaft, OBA, Ford 8.8 rear, 4.10 gears, tie rod flip, 1"MML/BL
2002 KJ Liberty, 2" Lift, 31" tires/DD
2002 F-150 Harley Davidson 5.4L SC
2013 Explorer Sport
2006 Harley Road King Classic
1988 Honda Hawk GT

Offline gearhead1985B

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Re: SOA or SUA
« Reply #3 on: October 29, 2009, 03:02:49 AM »
My opinion is soa on stock springs with a small shackle lift on a shackle reverseal for the front that will allow for the most flex and the smoothest ride and will clear 35's with no problem the problems with steering can be solved with a tie rod flip and a jb bracket (i will post the link to this when i get to my computer) and the other thing is a anti rap bar (got a write up on one of these that is very easy) the only down side is the cost of the whole thing soa is costly and time consuming but i believe that it is the way to go
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Offline Mr Rock

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Re: SOA or SUA
« Reply #4 on: October 29, 2009, 06:20:48 AM »
Thanks guys,
I was trying to stay away from  a body lift, but I guess thats what I will have to do.

I run 35's with 4.5" of suspension lift, a 1" body lift and still had to trim about 2" out of the rear fenders.  There are some really good advantages to the 1" body lift.  With the BL I was able to install a 1" Motor Mount Lift which angled the drive train to better align the drive shaft.  Also with the BL and MML I can do a belly up skid and gain 3.5-4" in the center of the Jeep which seemed to get hung up a lot back at BTC.  I can also raise the Gas tank skid 1" to gain some departure angle. 

Kirk,
When you trimmed your rear fenders did you still stay within the fender wells?
I guess I would need to install the BL and MML before setting the rear pinion angle?
'89, 4.2, NUTTERED, Team Rush, 4" Lift, 1" BL, 1" MML & HD shackles , Flat Belly Skid, SYE, 36 x 13.50s
XRC8, 150w KC's, Herculined, Tauras Elec Fan, Dual Batteries, Aussie in front, 8.8, TJ flares & Spool in rear, topless all of the time!

Offline kirksjeep

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Re: SOA or SUA
« Reply #5 on: October 30, 2009, 02:14:56 AM »
Thanks guys,

Kirk,
When you trimmed your rear fenders did you still stay within the fender wells?
I guess I would need to install the BL and MML before setting the rear pinion angle?

I only trimmed the back side of the rear fenders and yes I stayed inside the fender wells.  Since I am running Xenon TJ style flairs I managed to trim the fender and flair and with a few new holes be able to bolt it back in place and unless you look for it most people can't even tell.

I did the BL and MML after I had alread set my pinion angle.  It didn't cause any new vibs.  I figure the better angle will help when I get around to doing a belly up skid.
1992 YJ Sahara, 4.5 Rubicon Express ED Lift, 35" BFG MT, Custom Bumpers, SYE/CV Drive Shaft, OBA, Ford 8.8 rear, 4.10 gears, tie rod flip, 1"MML/BL
2002 KJ Liberty, 2" Lift, 31" tires/DD
2002 F-150 Harley Davidson 5.4L SC
2013 Explorer Sport
2006 Harley Road King Classic
1988 Honda Hawk GT

Offline rocket

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Re: SOA or SUA
« Reply #6 on: October 30, 2009, 02:06:17 PM »
so, for the few non-jeep guys, whats SOA and SUA stand for?
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Offline calvynandhobbs

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Re: SOA or SUA
« Reply #7 on: October 30, 2009, 02:08:30 PM »
so, for the few non-jeep guys, whats SOA and SUA stand for?

SUA= spring under axle as in how YJs all came from the factory
SOA=spring over or on top of the axle. Provides improved ground clearance since everything is on top, but takes a lot of work to set up steering and other things to make it driveable on the road.
1994 YJ on 37s

Offline Mr Rock

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Re: SOA or SUA
« Reply #8 on: October 30, 2009, 09:59:31 PM »
so, for the few non-jeep guys, whats SOA and SUA stand for?

Like Roger said.
It's a leaf spring thing.
'89, 4.2, NUTTERED, Team Rush, 4" Lift, 1" BL, 1" MML & HD shackles , Flat Belly Skid, SYE, 36 x 13.50s
XRC8, 150w KC's, Herculined, Tauras Elec Fan, Dual Batteries, Aussie in front, 8.8, TJ flares & Spool in rear, topless all of the time!

Offline Seabee_BUC

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Re: SOA or SUA
« Reply #9 on: October 31, 2009, 01:37:25 AM »
Yeah, just as strange as the whole square headlight thing...

Offline Mr Rock

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Re: SOA or SUA
« Reply #10 on: October 31, 2009, 04:46:03 PM »
Come on, it's hip to be Square!!!
'89, 4.2, NUTTERED, Team Rush, 4" Lift, 1" BL, 1" MML & HD shackles , Flat Belly Skid, SYE, 36 x 13.50s
XRC8, 150w KC's, Herculined, Tauras Elec Fan, Dual Batteries, Aussie in front, 8.8, TJ flares & Spool in rear, topless all of the time!

Offline reptile610

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Re: SOA or SUA
« Reply #11 on: October 31, 2009, 08:18:15 PM »
so, for the few non-jeep guys, whats SOA and SUA stand for?

SUA= spring under axle as in how YJs all came from the factory
SOA=spring over or on top of the axle. Provides improved ground clearance since everything is on top, but takes a lot of work to set up steering and other things to make it driveable on the road.

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Offline kirksjeep

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Re: SOA or SUA
« Reply #12 on: October 31, 2009, 10:19:20 PM »


FEEL ASHAMED!!! even i knew this.

You should know this, you have leaf springs :P
1992 YJ Sahara, 4.5 Rubicon Express ED Lift, 35" BFG MT, Custom Bumpers, SYE/CV Drive Shaft, OBA, Ford 8.8 rear, 4.10 gears, tie rod flip, 1"MML/BL
2002 KJ Liberty, 2" Lift, 31" tires/DD
2002 F-150 Harley Davidson 5.4L SC
2013 Explorer Sport
2006 Harley Road King Classic
1988 Honda Hawk GT