Flex is inherent in an IFS system, it's not as large as a SAS; but I'm talking strictly from a Stock/Coilover Lift sense vs. Bracket Lift.
Most of the bracket lifts I see are on Tacomas, Tundras, Sequoias, and FJ Cruisers; in those vehicle the installation & quality vary greatly. Even more are obviously meant as cheap slap-ons to fit skinny MTs and chrome rims to get that "Bro-Dozer" look more than actual off-road function.
For example, I see about half come in with just the bracket itself and no support bars; either the kit does not come with them or they were not installed; this means that the extended sub-frame bracket will have a tendency to bend back and forth under load and could cause issues later down the line. There's a reason you have the frame ties with those units.
Additionally MANY of the bracket lifts I see are not set-up correctly for the tire/vehicle combination they are meant for. A lot of the ProComp units I see on the Tacomas and Tundras show signs of heavy cupping on their fancy new tires (usually less than 5k and the tires are so cupped there's no saving them), this is a sign of incorrect spring & shock combinations as well as improper shock valving on the vehicle; most of the kits I see run either wimpy looking ProComps or just use a spacer on the factory set-up to make it work.
Which brings me to the other point, depending on the size of the tire/wheel and the suspension set-up you're running; you'll take out your compression and extension on your suspension (which equates to flex for us). For example, last time I went wheeling with a certain forum member who wanted 40's on his 4th gen, he'd went all out on a bracket lift and still kept the same Bili 5100's he had on his way overloaded rig for the longest time; when on the trails you could hardly see the truck flex at all, it barely compressed or drooped when on obstacles because the combination of bump stops and incorrect suspension set-up limited travel that much to fit his 40's. The obvious fix being to first start with beefier, longer travel shocks and springs and measure/adjust the bump stops to provide good flex/articulation while fitting bigger tires (last I heard he started doing this and the vehicle articulates much better now.) Looking at the first picture I would venture to say that the 5th gen with Yellow Wheels is probably set-up in the same "general" way I see many of the bracket lifts done and has little actual travel when off-road. I would really only look at a bracket lift if you want to run a larger than 35" tire, while it takes a lot of work (fender trimming, BMC, flatting pinch welds, adjusting bump stops correctly, good suspension set-up with a 3~4" lift, and at least a 1.5" Body Lift) you can fit a 35" tire onto a 4th or 5th gen and have it flex well with minimal rubbing. Any larger in tire size and you physically need to drop the sub-frame or hike the body up a lot.
Which comes back to other points made by the above members, not all kits are made or installed equally as I pointed above; this means there's potential issues that are not addressed. Pinion Angle, trailing link angles, and alignment set-up tend to be other factors that tend to be overlooked, untouched when doing these types of bracket lifts from my experience.
Bottomline:
If the bracket lift is set-up for the vehicle, tire, and suspension needs then it can function very well off-road (after all most of those Artic trucks are basically running exaggerated bracket lifts for those sexy balloon tires). But most of them are just slapped on for the "Bro-Dozer" look and thus will have limitations to suspension travel and flex and will affect the vehicle in negative ways, excessive tire wear, incorrect alignment, improper suspension tuning, bracket flex, ect.
It's not really my style as I don't really see a strong need for the J120/J150 platform to exceed 35" tires for most off-roading; but I do understand the need to use such set-ups for larger tire diameters. I've seen some very well set-up bracket lifts and I've seen far more incorrectly or improperly tuned set-ups (both Domestic and Toyota), much like any other mod for our vehicles it comes down to if it is done properly for the vehicle's current mod state and goals.
opcorn:
