corroded seatpost - got it out, what should i do to the inside of the tube?
 

the seatpost
http://img.photobucket.com/albums/v7...2/DSCF0811.jpg

the tube
http://img.photobucket.com/albums/v7...2/DSCF0820.jpg

the post is obviously trashed. what should i do to remedy any problems with the inside of the tube?


note:it was greased, obviously not enough. this was after 2 months. could storing the bike indoors during winter have contributed?

It's not that bad. Sand the seatpost lightly with oil and wet-n-dry sandpaper, 600-grit should even out that corrosion. On the seattube of the bike, spray some WD40 down there and run a brake-cylinder hone through for about 10-20 seconds:

http://www.naparts.com/Images/Produc...s/ph_11216.jpg

Wipe everything off with clean rags. Re-grease seatpost and re-install. :)

Storing the bike indoors may have been a contributing factor, but I doubt that it played a major role in your troubles. I would guess that water was thrown up from the rear wheel and entered the rear-facing slit of the seat collar, and was drawn down the seat tube. This type of water infiltration can generally be prevented by filling the slit with grease when you grease the seatpost.

It's a bit tough to tell from the picture, but the corrosion within the frame doesn't look like it will compromise the strength of the frame. It just looks like slight surface corrosion. It can likely be cleaned up with a rag and a wire coat hanger. Just cut and straighten the coat hanger, form a loop in one end, and then securely knot a small rag through though the loop of the coat hanger.

Some WD40 will help things along and allow the dislodged particles to stick to the rag for removal. Don't go crazy with the WD40, or you may thin the grease in your bottom bracket bearings.

The seatpost looks like it can still be used if you clean it up. A scotchbrite pad (like you may use on grungy dishes) might work better than sandpaper, but use whatever you've got. It's really not that bad. At least you caught it after two months. :)

If grease didn't stop the rust, spray a load of dedicated rust inhibitor down the seat tube and over the seatpost.

http://www.es-international.nl/TOOLS/SPECS/waxoyl.jpg

TBH, I wouldn't stick WD40 down the seatpost at all, it's about 90% solvent with the tiniest bit of light oil thrown in. I don't why it gets so much mention as a lubricant, it's pretty pathetic even as a "jack of all trades".

Great idea! When I wrenched at a bike shop, we used an adjustable reamer, but the hone looks like a winner.

I have used a bore brush for a shotgun with some steelwool wrapped around the 12 gauge brush to clean out seat tubes. Remember, you don't need a mirror smooth surafce. I think a few pits in the surface will even help hold the grease a bit better.

Some fine grit sandpaper on a dowel ought to clear off the corrosion. Use plenty of grease when installing the new post.

will cleaning off the corrosion on the post (as suggested above) be alright? should i worry about scratching off the anodization and having steel-aluminum contact? (hopefully with grease in between, but it seems like it would be a little easier for the corrosion without the anodization)

It's also possible, after all this junk is cleaned up, that there may be some nasty stuff down in the BB area. It depends upon whether the BB is bored through or not. Many are. You might be able to see that from the top of the seat post with a flash light. If it is, I would encourage you to pull the BB and clean it up, too. OHB

whoa. really dumb idea. Danno, I wish you would stop making thes types of suggestions without knowing what you are talking about.

You want to remove only the corrosion, not ream out the tube, that will weaken the tube and make proper seatpost fit impossible, ruining the frame.

LIGHT abrasive to remove any rust, then you can try a light coat of clear laquer to seal, make sure it dries for days, then a new seatpost with lots of grease.

A Brake cylinder hone will work fine if you stroke it right.It will leave a nice "cross hatch" pattern & hardly remove any tubing material.Just remember to keep the stones lubed.

I agree, and the seat post is clamped on the upper inch or so...

? :o

Right, reaming is a bad idea, but he suggested honing. That is a good idea.
Dan

So I take it you've never ever used the hone before and yet you pass judgement on my 10-years of using it a shop, eh? Blanket, all-or-nothing, black & white statements can't really compare to actual numbers. Here's what a brake-cylinder hone is used for:

1. master-cylinders in cars have piston pushing inside a bore with 0.0010-0.0015" clearance.
2. this gap is sealed with a rubber O-ring that's riding in a groove at the end of the piston
3. brake-fluid is anhydrous and absorbs moisture from the air.
4. over time, a year or two, the brake-fluid absorbs enough moisture that it actually starts to percipitate out of the fluid under cold-temperatures
5. these droplets of water eventually corrodes and rusts the walls of the master-cylinder
6. the corrosion and rust chews up the rubber O-ring and you end up with soft brakes, the pedal may even go all the way to the floor in extreme cases
7. So... you repair the master-cylinder by disassembling and using the brake-cylinder hone on the corrosion and rust present in the cylinder.
8. with WD40 or cutting-oil, 30-seconds with the hone typically removes 0.0002" of material (at minimal spring-tension setting). Usually a good idea to measure the cylinder and piston beforehand to ensure maximum-clearance of 0.0030" is not exceeded in the process of honing (reduce honing time if clearances are close to the limit already).
9. replace O-ring on end of piston with new one,
10. reassemble brake master-cylinder, pour in new fluid and you've got new brakes! :)

Note that the surface created by the hone is smooth enough to seal against 1300psi of hydraulic fluid with just a rubber O-ring!

With a seattube and cutting-oil, 10-20 seconds of the hone typically won't even remove the primer-paint that's sprayed down there! But it really does a nice job on the soft porous rust and other corrosion. It's much safer than reamers. You have to be careful with those and adjust them to the minimum since just 1/4-1/2 of a turn can take off 0.0020" of material instantly.

Next you're gonna tell me that programming the mill to take off 0.0005" from the surface of a corroded seat-post in my lathe is a dumb idea too right? After all you've probably done it a thousand times...

http://www.gururacing.com/imagesmisc/CNCmill.jpg

We use a doodad like this at our shop:

http://img202.imageshack.us/img202/7...tazione1qi.jpg

where can one purchase a brake cylinder hone, how much does it cost, and do you need a drill press for it or what?

never mind-- $10-15, attach to electric drill, available online & prob. auto parts stores.

To clarify....

The actual clamping surface on a seat tube, where it clamps the seat post is only a few centimeters long (an inch or even less). That's what secures the seat post from slipping or turning, unless the post is corroded tight further down the tube. My point is; if in the area below the clamp zone, the seat post is just a smidge oversized, the seat post clamp can still secure the post. Obviously, if it's way oversized, the post could shift some inside the tube, but a little clearance, like from a hone, shouldn't hurt. Follow?

Take a dowel, put it in a drill, then wrap some steel wool on it and apply some light oil and spin away. Try to get a good size dowel and enough steel wool to be snug not tight this has worked for me on a couple of times on similar problems.

Yes :)

WAIT!
That's a HONE! :D

OOOOOOO!!!
Look at all the pretty buttons to push & twist! :eek: