Tight Seatpost Installation I'm having a bit of a problem installing my seatpost.  

I have a 31.6mm carbon-wrapped aluminum seatpost which fit perfectly fine in my previous aluminum frame.  Unfortunately, that frame cracked, but I found the exact make, model, and size frame on eBay to replace it.  The only problem is that the seatpost doesn't fit into the seat tube very well.  It is a very tight fit, and I can only get it down 1 1/4" before it gets really difficult, even with a bit of grease. 

The top of the seat tube doesn't appear to be crimped, so I'm not sure what the problem is.  I'm a bit gun-shy since I've already broke a frame this year.  So, I'm not sure whether to force it down, use a rubber mallet, or buy a new seatpost.  

How do I determine if it's possible to fit this seatpost in this frame safely? Is it possible there's something else interfering with the installation, or will I need to buy a new seatpost?
Never use a hammer.

In order to check the inside of the frame, visual inspection most times FAIL, because the problem is caused by tiny bumps or misalignments that are not easily seen with naked eye and even felt with fingertips.

I would recommend that you take another seatpost (an old one you can take/borrow on a local bike shop) and try to insert more aggressively. You should polish the seatpost first someway (steel wool, for example).

You force it inside a bit, then take it out. Probably, there would be some marks on the seatpost surface, suggesting if there is some irregularity inside the frame. Most common are bending around the vertical cut around the clamping nut, or deformation caused by welding the tubes around that region too deep (to the point of almost melting the inside of the tube.

The seatpost tube of the frame might be not-straight, which would be a manufacturing defect.

In the end, you could polish/sand/grind inside the frame to make the seatpost go down easier, but since seatposts that don't go down so easy come out very hard afterwards, and your post has a carbon surface, taking the frame to the bike shop to check if it needs replacement or special service (with machining tools to improve surface quality and alignment) could be necessary.