Rear Spring Question - OME BP-51 2721 v 2722 w/ 12.5 LRA Tank, Sliders & RTT?

[TeCKis300]

Throwing this out there since I don't have an LC or a horse in this race.

From purely a spring rate perspective, it would seem that the 2721 would be easily enough. It's not an insignificant jump to go 60% in spring rate given the following data. (then again, the 2722 are spitting distance in rate and actually would be softer through resulting travel being linear).

Stock: 170
2721: 270/350
2722: 275
2723: 340
2724: 400
2725: 440

Part of what we associate with spring rate is ride height. That's not exactly the case as that really depends more on the free length of the spring. Perhaps the free length of the 2721 and resulting ride height isn't high enough and that's where the criticisms of the 2721 comes from? Ideally, spring rate and free length/lift are tuned for independently. But we're also stuck with the reality of available options on the market.

Just me, but if I had an LC, I would choose the softest suitable spring rate for the likely normal weight of the vehicle. This will give the best ride quality, while also performing best off-road with maximum articulation. If that spring doesn't result with enough lift, use spring spacers or trim packers to get the target ride height. Then to address fully laden trip weight, support with airbags, which gives adjustability to increase spring rate for load, ride height, and stability.

EDIT

Here's a great post with additional options beyond OME

Ok I've spent obscenely too much time on this. Bumper is painted and ready for installation this weekend. Pre-bumper I have the Tough Dog TDC931L springs and when I'm loaded with family and cooler I sit very level (no rake), or a bit of squat if I have the trailer hooked up... measurements below from top lip of my 17" Icon wheels to the fender (I used that instead of the center hub because it's hard to determine the precise center):

Setup	LF	RF	LR	RR
Vehicle only, airbags at 5psi	12	12.5	13.5	14
Trailer hitched, no weight dist.	13	13	11.5	12.25
Trailer hitched, WD set	12.75	12.5	12.25	12.75
Trailer hitched, WD set, 30 psi	12.75	12.5	13	13.25

I've got about 1.5" of rake when empty right now. I'm running about 1" of squat when trailered but otherwise unladen with no family or camping gear (1/2"-3/4" too high in the front, 1/2"-3/4" too low in the rear). Laden with family and dog and it's another 300# in the rear. And I haven't yet added 200# of bumper plus all the leverage associated with crap hanging off the rear. Thus even without have actually installed it yet (hoping to do it this weekend) I'm pretty damn sure I will need to step up the rear springs. That said, without the trailer but with an extra 300# in the trunk (kid + dog) the ride is spot on plush and perfect right now.

I charted all the rear spring options I could find that would be relevant. Info below is what the vendors claim. My setup is in green. Options I'm currently considering are in orange. It's interesting to me how some of the numbers line up but others don't. For instance the heights, coil wraps, wire diameter, and #/in ratings between the King KTRR-131HHD and OME2723 are nearly identical, but the King spring is rated for 100kg more constant load. They also look similar to the Tough Dog TDC931VHL spring but that has a minimum constant load rating at the top of the King and OME max range - and that plus my current experience with the basic Tough Dog spring makes me think the constant load ratings somehow matter more than the free height, wire diameter, and compression specs. OME and IronMan spring options are half the cost of the Tough Dog and King options in the USA... otherwise I'd likely just step up to the next TD spring.

vendor	part #	l/h mm	r/h mm	coils	wire mm	low lb/in	high lb/in	min load kg	max constant kg	min load lb	max const lb
King Springs	KTRR-131H	450​	470​	7.2​	18​	240​		100​	250​	220​	550​
King Springs	KTRR-131HD	430​	450​	7.2​	19​	275​		100​	300​	220​	660​
King Springs	KTRR-131HHD	430​	450​	7.2​	20​	340​		300​	500​	660​	1100​
King Springs	KTPR-131HD	435​	455​	8.4​	19​	250​	350​	100​	300​	220​	660​
OME	OME-2721 0" lift	430​	440​	8.42​	18.5​	270​	350​	0​		0​
OME	OME-2722 1" lift	430​	440​	7.2​	19​	275​		0​	200​	0​	440​
OME	OME-2723 1" lift	440​	450​	7.2​	20​	340​		200​	400​	440​	880​
OME	OME-2724 1" lift	435​	445​	7.2​	21​	400​		400​	600​	880​	1320​
OME	OME-2725 1" lift	435​	445​	7.71​	22​	440​		600​		1320​
Tough Dog	TDC931L 1" lift	445​	475​	7.2​	18​	240​		0​	300​	0​	660​
Tough Dog	TDC931HL 1" lift	425​	455​	7.2​	19​	275​		300​	500​	660​	1100​
Tough Dog	TDC931VHL 1" lift	425​	455​	7.2​	20​	340​		500​		1100​
Bilstein	B12 53-297686							180​		396​
Eibach	E30-82-072-04-02	414	414			300		90​	180​	198​	396​
Icon	Dual Rate 52750					?	?			0​	0​
Trail Tailor	Tourflex Standard	505​	515​	9.77​				100​	300​	220​	660​
Trail Tailor	Tourflex HD	545​	555​		19.5​	180​	320​	300​		660​
Ironman	TOY064A 1" lift	425​	440​		19​	269​		0​	200​	0​	440​
Ironman	TOY064B 2" lift	455​	470​		19​	269​		0​	300​	0​	660​
Ironman	TOY064EA 2" lift	465​	475​		20​	286​		100​	400​	220​	880​
Ironman	TOY064C 2" lift	455​	465​		21​	371​		400​		880​

 

[FJ Dude]

Thanks for that info. I will have drawers, a Dissent rear bumper and eventually an LRA tank. I am thinking about the 2723's.

 

[100kiwi]

Thanks for that info. I will have drawers, a Dissent rear bumper and eventually an LRA tank. I am thinking about the 2723's.

I have drawers, Kaymar rear and the 12.5 tank on 2723s. They are a good match for me. With the RTT and all loaded up for camping I still put 20psi in the rear air bags on the hwy