Shims?

[Cherokeekid88]

Ok well Im getting some LA's fabbed and thats where all my money is going to. I was originally gonna invest in an SYE, but that can wait. But in the mean time, I would like to try to eliminate the minor vibes I am having. I currently have a TC drop but it only eliminated 97% of my vibes. While im swapping axles i would like to throw in some shims for the time being to try and rid those vibes, then save up for an SYE. Im sitting at 4.5" of lift and read that 6 degree shims are the way to go? Also whats the deal with the aluminum ones? Are they that much worse to use than the steel ones?