Spring Under Axle SUA Conversion Facts For Tacoma 2nd/3rd Gen

If you care about getting the best setup on your truck and can trust my experience, (I did the Mid Travel SUA conversion on my personal Tacoma), please read this to understand more about Mid travel Spring Under Axle conversion specifically for 2005-2022 Tacomas, before you make a choice that could be a mistake.

"Mid travel SUA" refers to SUA springs that fit in stock hangers, that can achieve 12" travel to 14" max shock travel.
(Long Travel SUA is 16"+ travel with long springs that get moved outboard on frame, requiring all new hangers, and shocks through the bed with a bed cage or cantilever mess)

There are many claims made about Spring Under Axle conversion, and how it will accomplish this or that. But there are so many generalizations taken by people without any experience or factual knowledge, and the internet runs with it until rumors and falsehoods become accepted.


Statements that are actually NOT true about Mid Travel SUA, but many state as fact:

· “LeSs aXlE wRAp”. This is false on the 6-lug Tacoma being converted to SUA! Because the new perch is now below the axle with SUA(~5" lower than stock perch), the drive axle pushes the truck forward thru the leaf pack and the leaf pack applies force to the front hanger at an upward angle, which puts more bending force on the main leaf and flexes the leaf pack. SOA is better here as the main leaf pushes near horizontal at the front hanger, parallel to the direction you are accelerating the truck.

· “SUA rides better”. This is a big over-generalization. Leaf spring ride quality largely depends on the spring rate vs vehicle weight. Put an HD SUA pack in a stock weight Tacoma and it will ride like garbage when unloaded without the intended weight. I tried this in my truck, the ride was jarring due to high spring rate with OE tension shackle arrangement.

· “SUA has more bump travel”. This may not be true! It depends on the kit design and thickness of whatever SOA pack you are comparing it to. A popular Mid travel SUA kit from a trusted quality name in the industry has virtually the same bump travel as the stock leaf pack due to the tall bracket they supply that gets welded above original spring perch. IF you're not getting more bump travel, why even do the SUA conversion at all? By getting lift with SOA, you may be able to have the same bump travel as, or more, than converting to MT SUA. The truth hurts sometimes.


The Actual Compromises of SUA:

· SUA conversion costs more in parts, labor to weld, and time to properly setup

· SUA causes more rear sway because the new axle perch is moved below the axle, and that vertical separation between the hangers and the leaf perch means the main leaf is affected more by side loads. The axle pokes out a bit in a corner and you feel it

· SUA causes a loss of ground clearance

· SUA has very limited spring selection for MT, making it hard to easily find a good spring rate and lift combination for the varying truck uses out there.

· SUA is a bad option for towing, hauling weight, and therefore expo/overland rigs. SOA is clearly better here.

· SUA often leaves you with not enough lift, this means your truck will be much lower in the rear while towing, or it will be dragging bumpers on rocks off road


The Best 12"-14" Mid travel setup:
I have found the best 12"-14" setup for the 2nd/3rd gen Tacomas is to stay Spring Over Axle like stock, get 2-3" lift with quality US made leaf springs, and use the best, properly designed parts to achieve 12"+ (shock) travel out back, and focus on conserving your bump travel. If you do that, it gives the best ride, best handling, best weight hauling, best clearance, best all around performance for most uses, including rock crawling, expo rig use, towing, and even corner handling.


Archive 2005-2023 TACOMA ULTIMATE OFF ROAD 12"-14" TRAVEL PACKAGE W/ LEAF SPRINGS
https://archivegarage.com/shop-archive/ols/products/2005-tacoma-ult-pkg-with-springs

 

Saved for future use

 

Just commented about this on your other thread. Looks like I'll be purchasing some HD springs.

 

Still thinking about this 2 years later. Wanting more rear uptravel for spirited beach driving. Already have 14 inch rear shock relocation (through the bed), hydro bumps, 4 inch rear archive shackle and hammer hangers with cross tube.

I have no problem redoing the lower shock mounts to put them lower to account for the extra uptravel.

I don't care about cycling 20" of travel, just want another 2 inches of uptravel to be able to not be bouncing off the bumpstops.

Truck hauls air and I don't even have a trailer hitch.

What's your thoughts on running a deaver light duty spring on this type of setup?

 

With Deaver Light Duty (U644/645?) Mid Travel springs, you'll have zero lift, and therefore sadly the same bump travel.