Topic: SUA vs SOA

[neale_rs]

This question is mainly for oldjeep but it would be good to get any and all opinions from members.

oldjeep,

You have an SUA YJ.  With your mechanical and fabrication skills you could set up your jeep with SOA about as easily as anybody.  What are you reasons not to do so?

Thanks

[aw12345]

Probably axle wrap, a friend of mine has a CJ7 with a 4.5" lift on it and he has a heck of a time keeping his Jeep on the road. The thing wanders from the rear accelerating/decelerating

[Jeffy]

I like BOTH... 

[Bounty Hunter]

SOA on my YJ, now have to add traction bars to contend with the axlewrap.  I didn't think the 2.5L would twist the axles much, maybe it's the 5.38 gears

I run relatively flat springs, I like the added lift of SOA without having to run stiff arched springs.

[oldjeep]

This question is mainly for oldjeep but it would be good to get any and all opinions from members.

oldjeep,

You have an SUA YJ.  With your mechanical and fabrication skills you could set up your jeep with SOA about as easily as anybody.  What are you reasons not to do so?

Thanks

Pro
1) SOA will tend to be a more flexible and gives you some more ground clearance at the springs

Cons
1) it's also a lot harder to make it behave on the highway.
2) Cost - everyone who has never done an SOA says they are cheap, just put the axles under the springs and go.  BS.  You need to address the steering problems, generally with a high steer setup.  You need a rear traction bar or you will be destroying springs, driveshafts and pinion yokes.

 It's very easy to set up an SUA YJ and make it work safely and reliably, and if you are going to be driving it at 75 MPH those are important things.

[neale_rs]

Thanks for all the replies.  I'm going with SUA.  My main reason initially was to avoid fabrication and having to work out all the complications of SOA.  Since the YJ will be driven on the highway to get to trails it sounds like SUA was the better choice for me.

[Bounty Hunter]

My SOA YJ drives just fine down the interstate at 80mph.

You would need to do the same mods between the SOA and SUA if using the same amount of lift, minus having to weld on spring perches.  Comparing apples to apples here and not comparing a 6" SOA lift to a 4" SUA lift.  You can get away with a lot fewer mods at 4" regardless of the type of lift.

A SOA will outperform a SUA lift any day, a flatter spring has a much larger operating range and a better onroad ride.

[neale_rs]

I really didn't want too much lift, just enough for 33s.  I have a few jeeping buddies who run SOA and also say it is fine but they have complained about lean on off-camber slopes.

[oldjeep]

My SOA YJ drives just fine down the interstate at 80mph.

You would need to do the same mods between the SOA and SUA if using the same amount of lift, minus having to weld on spring perches.  Comparing apples to apples here and not comparing a 6" SOA lift to a 4" SUA lift.  You can get away with a lot fewer mods at 4" regardless of the type of lift.

A SOA will outperform a SUA lift any day, a flatter spring has a much larger operating range and a better onroad ride.

Out of curiosity, what did you do to your steering when you went SOA?  In otherwords, where is your tierod?

[Bounty Hunter]

My tierod was initially under the springs, now it is over the springs with BTF highsteer arms. 

With it and my draglink under the springs I had too much bumpsteer, same problem you would have with the same amount of lift SUA.

SUA is a good choice for 4" of lift and 33" tires.  I'd even recommend 2.5" springs and TJ flares to keep the center of gravity lower.

IMO for 35" tires and larger, SOA is the best route.  I was installing D44's anyway (needed for proper gearing) so SOA was logical.

[oldjeep]

My tierod was initially under the springs, now it is over the springs with BTF highsteer arms. 

With it and my draglink under the springs I had too much bumpsteer, same problem you would have with the same amount of lift SUA.

SUA is a good choice for 4" of lift and 33" tires.  I'd even recommend 2.5" springs and TJ flares to keep the center of gravity lower.

IMO for 35" tires and larger, SOA is the best route.  I was installing D44's anyway (needed for proper gearing) so SOA was logical.

So you've got a Dana 44 in the front, not a dana 30.  This is how most SOA vs SUA discussions start, when the guy with SOA forgets about all the mods that he did before switching to SOA.  And by your own admission, you've currently got an axlewrap problem in the back - which is a common problem when people do a partial SOA conversion.

Bumpsteer on a SUA YJ with 4" lift is solved with a drop pitman arm or tierod flip.  Although with a 4" SUA lift 5/8" shackle lift and stock steering, mine is decent enough on the highway - with plans for a tie rod flip.  4" SUA, 5/8" shackle lift and TJ flares is plenty for 35" tires and is a nearly bolt on setup.

[Jeffy]

Hmmm, I see there are some misconceptions with SOA's.

If you''re already lifted 4" or more then a SOA is fairly simple to install since you won't be gaining that much more height.  When I decided to go SOA on the front of my Jeep,  it cost me $30 for the perches and $150 for two stock leafs springs.  Everything else was carried over from the SUA.

Steering is no different SOA or SUA.  The only real difference is that the SUA is going to be stiffer so it moves less.  But that's because of the leafs and not because of any corrections to the steering geometry.  Because of this, you will see more bumpsteer then with a SUA generally speaking.  Now if you raise the spring rate of the SOA, it will reduce the bumpsteer.  Adding a trackbar to the front will help a lot since that really stiffens up the front.  I'm just running the stock arms with a dropped pitman arm currently.

The rear?  Well, I didn't want to deal with axle wrap so I kept it SUA.  It flexes a bit less then the front but it's not bad at all.  Otherwise, adding a extra main leaf to the stock leafs would help alleviate axle wrap.  If you really wanted to do it right then getting some SOA springs from Rubicon Express would probably be best.  At least for an off the shelf solution.

As for highways, you adjust to it.  Although with my SOA/SUA setup, it's a bit more surefooted then if I went all the way.  With the sway-bar attached, the front is well behaved.  75mph is smooth and tracking is fine.  Emergency braking could be a bit better but that's fixed with high-steer.

Offroad, though, it's a big difference.  The front actually flexes.  Instead of three wheeling, you'll have 4 down.  The ground clearance is a big plus.  If you do rocks, you'll be dragging your leafs.  This is actually a problem with SUA's that have custom leaf packs.  To get a softer ride but have the added spring rate of a thicker spring, they have to use thinner leafs but more of them.  The problem this causes is the spring pack can get rather big.  If you look at some older Jeeps that have National Springs leafs, you'll see they are usually 9 leafs to a pack and are huge.  They flex really well and ride smooth though.

Although you're really opening up a can of worms, asking a person to defend their choice.  It's a personal choice and is really dependent on their local trails as much as a personal preferance.

[oldjeep]

Jeffy, Have you got a picture of your tie-rods in relation to your springs?   Every SOA YJ I have ever seen that uses the stock YJ steering has the tierod or drag link hitting the leaf spring when flexed out.  How did you get around that?

[oldjeep]

This is what I was looking for.  What happens when you crank the steering to the right and stuff either front wheel?  Have you got the perches jacked up enough or the knuckles tiped back so that the draglink doesn't hit the spring?

[Bounty Hunter]

This is how most SOA vs SUA discussions start, when the guy with SOA forgets about all the mods that he did before switching to SOA. 

D44's were at the SAME TIME as the SOA, which made the swap that much easier.

When I had my draglink under the springs, it did not contact the spring pack when at right full lock.  I was using Waggy steering linkage and GM knuckles where the tierod goes into the steering arm from beneath.  Couldn't use the Waggy knuckles because the TRE's go in from the top.

Rear axlewrap isn't much of an issue for me to avoid the advantages of SOA, it's easy to deal with.  Just unexpected.  And I'm using stock YJ spring packs with an additional full-length leaf in each pack.  I cut the extra leaf half-way through the spring eye so it wraps up the spring eye of my existing spring pack, giving good support to the weakest part of the main leaf.