to answer your question yes you should take it down to raw metal because the jb weld will be able to better bond your seatpost and frame use a fine grit sandpaper something above 110 should be good
For something like this I would think that a low grit sandpaper would make more sense. Those scratches would give the epoxy a little more bite.
All I can say about this idea is, don't be surprised when the JB Weld breaks and you're left with a mess to clean to up.
personally i thing that either doing something like this or getting a macneil nub post would be a much more effective way of getting your seat just as slammed.
How can you know tig and mig welding but have never heard of JB Weld?
I see no reason at all to do this, pointless endeavor. You are just going to screw it up and destroy your frame... and for what?
dude who the f*ck said im screwing up my frame, have faith im not a retard
You will screw it up... do you know happens when you bond dissimilar metals together? Galvanic corrosion. Could be a problem. But hey, your bike, your money, your disaster.
It will not cause Galvanic corrosion, but I do agree that it is one of the most ignorant mods I have heard of to date.
If you really want to weld the post to the seatube, sand it down to the bare metal (I suggest like 80 grit(gets it down to metal faster)). And I suggest either a tig or mig weld, it would hold up a lot better than what this JB stuff sounds like.
And it will more than likely void the warranty.
And DK you could easily change the post I already know 2 ways.
1- Plasma cut the weld between the post and tube, then file it down smooth.
2- Hack it off with a saw, and file it down smooth.
EDIT: Please don't cut your seat tube, it will viod the warranty on the frame, and it will make the seat tube weaker (because you will probably cut it down to near the welds) and that takes a decent amount of stress.
thats what you want. It saves you the effort, and destroying your frame. You can cut your frame seattube at the top completely off, then u just stick this in, tighten the wedge, screw on your seat and its uber slammed. It also allows you to potentially adjust your seat in the future or get a new one. Think about it. IF you glue your seat post to your frame, and then your post bends... now what?