yes, they are worth it on a number of levels.
guys with tundras over the years have had trouble with the springs that fit the 2.0" shock bodies, once they start running a winch with an aftermarket "armor" bumper. it's just too much weight for the smaller diameter springs to support laterally, and they eventually bend in the middle...like a banana. think of compressing a click pen spring...it tries to bow to the side, and smaller diameter springs will do the same thing. the springs are shaped different from oem springs...straight profile, no coning at the spring seat on the shock like oem.
the springs that fit the 2.5" bodies seem to support the load better. as far as the shock body, unless you're running the baja, there is little difference between a 2.0 and a 2.5 body...really, theres no need for a 2.5" body on tundras, tacos or runners for our purposes...but youll want the wider spring once you load it up.
eibach and...ummmm...hyperco? whoever makes donahoe's coils...are both quality. i dont remember who made the old "swayaway" branded coils from a few years back, but i did manage to thoroughly fatigue a set on a fully loaded tundra with the v8 and an arb bumper, no winch. the new donahoes reportedly have a very, very good spring. it is shorter (13") but not wound as tight as the 15" eibachs on the front of my truck. the length doesnt make a difference, it's not possible to overextend the spring in the stock location on toyota ifs, the springs are just designed different. ive never coil-locked the 15" eibachs. dunno how the eibach and dr coil stack up over time as relates to fatigue, i havent had a chance to flog the eibachs the way i did the old saw coils. the dr coils are supposed to fatigue less over time than everything else, goes the marketing pitch. you cannot go wrong with the dr setup. the camburg-badged saw is also a very, very good shock, and they offer a package deal with their uniball upper control arm.
the great advantage of an adjustable, rebuildable coilover is you can usually choose your spring rate depending on your application--winch, no winch, prerunner vs armor bumper, etc--and when (not if) you emulsify or otherwise damage your shocks over the years, you can either rebuild them yourself or send them in for a rebuild (if emulsified, hard to diy due to compression requirement at the seal, and messy...but dr and saw have great customer service and quick turnaround time).
also, since youll be changing things around over time, you can adjust the ride height as you add sliders, skid plates, bumper, winch and other toys.
the new springs will be stiff, and unless you weight the truck properly for the new spring rate, you do run the risk of damaging things.
the higher you push the lift, the harsher it rides...as the static position of the lca drops, the tire has to move outward more in order to move up, so youll feel more bumps. it might not look like much, but youll notice when you pick up the front end, then set it down again, it sits higher than normal until the tires can scrub out to their normal position. go too high and youll be hitting the extension stops on the shock every time you go over a bump.
youll immediately notice a difference in handling due to the valving. youll also notice a difference in unloaded street handling, since it'll ride like it's on rails, but thats because the springs arent loaded properly...offroad, unloaded, it'll be "interesting". i'm having this problem right now since fiberglass and bumper mods weighs a lot less than sheetmetal and "stock" bumpers. once its loaded up, it'll ride like a cadillac.
youll never look back to non adjustable, non rebuildable coilovers
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i know we've been talking donahoe and now ive mentioned swayaway, there are also fox and king...but dr and saw have the most presence in the toyota community, they are active on several of the major online forums and their customer service is extremely good--very, very good people at both, all very supportive of the spectrum of users, from racing to weekend adventuring
-sean
*edit* sorry, i mustve been writing that at the same time as bajataco
...some more info, then, and definately read his linked post. a couple more comments from me...the 14" 2.0 coils are rated at 650#, the 15" are 675#. the difference is about a single wrap (pitch is ~1 wrap per inch). you cannot go wrong with the eibach coils, from everything ive heard. i got them (the 15s) through kartek and replaced the 14" saw coils that i fatigued to 13" via a good desert pounding at ~3T gvw. kartek is great for replacement parts, if you wanted you could buy an entire coilover piecemeal from them and assemble it yourself. extremely helpful there also.
never, ever adjust your coilovers on the truck, unless you *absolutely* have to (shouldnt ever be the case). they are easy to take on and off, it's far easier to adjust them on the bench, and you'll avoid galling the aluminum adjusting collar on the steel shock body--theyll corrode together and then you have to cut the collar off with a chop saw, assuming the coil isnt loaded when its off the truck! i used cv grease, but superlube (teflon) would probably work better. gunk the stuff all over the area where youll be turning the adjusting collar, adjust them off the truck (might take a try or two, but it's worth it, and donahoes come adjusted at iirc 2" lift from the factory anyway), check the height on the truck, once youre satisfied (use a caliper to check differences in height between the lca and bumpstop, make it equal so the truck can be aligned easier), wipe the excess grease away--dont sweat the grease under the coil next to the collar, it will help in the long run--then put a big, fat fillet of clear silicone sealant--rtv--in the corner between the adjusting collar and the exposed threads (not the side with the spring). run it up the exposed threads an inch or so, and at least halfway across the adjusting collar surface, all the way around. it comes off very easy, and prevents moisture from penetrating the threads between the adjusting collar and the shock body. the clear sealant lets you see the condition of the threads...if you need to adjust them, just pull the rtv off, clean the exposed threads with a wire brush, grease thoroughly, and adjust as necessary. that procedure has lasted two salty midwest winters and i'm still able to adjust the collars.
