PREPARING THE SEAT TUBE CAVITY

The first thing one should do when preparing the seat cavity is carefully clean out the inside of the seat tube.  Clean the inside of the tube at least as far down the tube as you can reach.  The purpose here is to ensure that the seat post will slide freely into the tube.  The use of a soft brass wire brush will really help with this task.  BE CAREFUL:  You will be sticking one or more of your fingers into the opening when attempting to clean out the tube.  There just might be sharp metal burrs in there, that will cut flesh in a wink of an eye.

The best tool to use for this task is a small brass wire brush.  These brushes are available in most hardware stores and do not cost an arm and a leg.  This small brush will prove to be very useful in a variety of tasks related to restoring or maintaining a vintage road bicycle.  The brush is great for cleaning chrome surfaces and even polishing alloy components once the brush becomes well broken in.

With most of the heavy gunk wire brush removed, apply a bit of WD-40 to the inside of the tube and then begin the process of wiping it clean.  You don't have to soak everything is sight.  WD40 is a solvent and, even though it is a great product, using it is bad enough.  Over using it is even worse.  A rag, balled up and then forced/twisted, with the assistance of a screwdriver, into the opening will be a great benefit to help dry and wipe out the cavity.  Do not push the rag so far into the tube that you cannot get it out again.  It is helpful if you secure the rag to a straightened out wire clothes hanger and use the combination to clean out the seat tube.

After this initial cleaning, take a look and a CAREFUL feel to see if there are any obvious burrs.  If so, remove them using an assortment of small metal files.  I use a three point, a round and a half round, all six inches in length, or so, will do the job nicely.  Once filed smooth, clean sparingly WD and check to see how the opening has improved.

It is a good idea to round off all internal edges in the seat tube opening.  The vertical slot that allows the seat lug to squeeze together often time has rough edges.  These need to be smoothed off.  So to do the edges of the opening itself.  As you work, continue to feel for rough or sharp edges.  You want to make sure that they are all gone when the task is complete.

Once satisfied that things are as clean as you can get them, a very light sanding with very fine emery cloth will remove slight high spots that might remain.  Once lightly sanded with the emery, a final wipe with a clean rag completes the task and while completing this phase of the exercise, push the rag all the way into the bottom bracket cavity.  Doing so will remove all debris that could be in the seat tube.  Debris that will fall into the bottom bracket cavity and bottom bracket bearing later on if not cleaned out now.

There is good reason to ensure that the seat post cavity is as clean and smooth as you can get it.  Once prepared properly, the chances of damaging your, sometimes expensive, seat post with burr scars is dramatically reduced.  And of equal importance, not just to the seat post but also to your frame, is the fact that the seat post clamp bolt will not have to be over-tightened, to achieve adequate clamping support.  Less torque on the seat post bolt, will result in less strain on, and possible distortion of, the seat tube lug.

NEXT - REPAIRING THE SEAT POST LUG