I'm new to this site and looking to get some advice/help. I've got a 2008 GMC Sierra 1/2 ton, and I recently picked up a set of 20" KMC Spy's with Nitto Terra Grapplers. It seems something to do with the wheels packadge is causing some shaking and vibration when I'm braking. It doesn't always happen, and it gets worse the higher the speeds. I've had the computer checked and nothing shows, also pulled the fuse on the ABS and no change. It all goes away when I switch back to the stock wheels. Any suggestions or advice? I've talked to the place I got the packadge and they are saying it's something to do with the truck. Thanks alot!