when i use my rear brake it sqeaks like hell and practicly new whats the deal
Stop using it...duh...j/k
Its a common problem with the GS, in fact its on of the problems with my bike.
Solutions:
Swap the postion of the shims
Swap the postion of the shims and put on some anti-squak stuff
Swap the postion of the pads
Lube up everything in there that moves(expect the friction surface)
ANd my personal favorite
Put some cotton balls in your ear :)
Ohh yeah, pop the little plastic cover off the top of the rear caliper, and take a look at your pads, they simply could be worn down to far..
Get used to it, I just rolled over 3000 miles and mine still squeak. You could try some of the following old threads though, I haven't bothered to try and fix it, it squeals so loud everyone turns to look at me. I figure as long as they see me it's a good thing.
http://www.gstwins.com/forum/viewtopic.php?t=3428&highlight=rear+brake+squeak
http://www.gstwins.com/forum/viewtopic.php?t=10865&highlight=rear+brake+squeak