Had a think about this a bit more after looking at the above discussion of reaming seat-tubes, Ti or not. Also took
some measurements from my own fleet and did some calculations.
While I can't be 100% sure, because of the absence of a factory fitted AL shim, I'm guessing the GT (being cheaper and Asian made) uses a straight gauge vanilla flavoured seat-tube with no fancy internal or external butts or spiral ribs and whatnots.
OD let's say 31.7mm. Minus ID 27.4mm gives a theoretical wall thickness of 4.3mm / 2 = 2.15mm. Let's say 2.1mm then.
Compare this whopping 2.1mm to these ..... which are about 0.9mm thickness and must have an AL shim:
DEDACCIAI K-19 3/2.5 Ti Gr9 31.7MM DIAMETER SEAT TUBE COMES WITH ALUMINUM 27.2 SLEEVE INSERT OR CAN USE A WELD INSERT COLLAR SKU -TBEK-MTV317T101 CLICK HERE FOR SPEC SHEET 31.7 Ø X .9 X 620MM 245 GRAMS 3/2.5V Gr 9 SEAMLESS TITANIUM BKS STATE (DRAWN
www.bikefabsupply.com
BT 122
www.ticycles.com
I think you could safely follow pete_mcc advice back on page 3. Taking off
only 2.5% material from the wall thickness
represents an internal diameter increase of about 0.1mm which would probably help enough to remove the bind point.
Somebody more into framebuilding would be able to make a proper judgement call. It's a tricky one, because while seatposts can be filled down more easily it doesn't actually repair the frame that is at fault. It feels like messing around with seat-posts is trying to get two wrongs to become a right. Beer can shimming with a 27.2 post would work too, but this frame may be a bit too good for that and deserve a more permanent fix.
