I can't speak as to the spring wear...I could swear I just started noticing mine sagging, but I hardly think it's due to the month and a half I've had the SLR shackles installed. Anyway, I just wanted to say--you don't need shackles to clear 32" BFG MT's...MT, FSRBiker, Synchro, and I believe Mosi (among others) all ran/run those tires without the extended shackles with little/no problems.

Nonetheless I see no reason not to do this mod, so long as you don't mind having a raked X again.

Thinking about it, I've heard that inverting the arch of a leaf-spring is what really stresses/sags them, and it's probably easier to do that if you do have the shackles installed. Either way the anecdotal evidence suggest that if you offroad w/ more than about 100 pounds of stuff in the back of your X, your springs probably will need replacing at some point before your warranty is up. Me? I'm probably just going to wait and replace mine w/ the SLR/National springs...

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Vikram/gothamist -- MAXC member
http://www.4x4LO.com