I picked up a used GT STS (I believe an STS 1500 DS although the stickers are missing). The bike rides nice and I'm looking forward to taking it on the trails.

One problem is that when I bought it a damaged post was jammed in the seat tube. A 31.6 mm non-OEM post had been overtightened causing it to bulge and then the bulged area was pushed forcefully into the seat tube causing it to jam.

Now that I got the post out, a new post doesn't go in and out easily. The inside of the seat tube is a little buggered up from removal of the jammed post.

  1. What can be done to clean up the inside of the seat tube? ( on a cro-mo bike, my LBS has a reamer thingy for a drill that will clean out the inside but for aluminum lugged carbon fiber probably not the ticket)
  2. Is using a shim (say a 31.6 to 27.2 shim) a viable option, provided the shim meets the required 4.5 inches of insertion?
  3. Is 31.6 mm the correct diameter? My research on google indicates that for a 1998 GT STS 1500 DS it is correct.


Thanks for any help you can provide a new GT owner.