Totte86

Hello!

I have heartbrokenly damaged the seat tube of my newly acquired frame with reynolds 531ST tubing .

Please see pictures in this album:
bikeforums.net/g/album/23836293

I was thinking to repair this by running a greased up 26.9mm steel pipe(seat tube inside diameter is 27mm) with the end of it sloped to be as gentle to the seat tube as possible. Also with a notch cut out in the pipe for the bottle cage hole, the hole It has a slight protrusion inside the tube.

Would this be ok or are the dents too deep? Would I make it even weaker by pushing it out even if the repair goes well, is the tube stronger if I just leave the dent and try to live with it? I don't want to try to roll it out with frame blocks cause of the bottle cage protrusion on the outside and I don't want to mess up the paint. I obviously don't know how weak and thin bicycle tubing is or I would not have managed to damage it in the first place so I'm asking for help from the experts .

Thank you for any help!

Nessism

That dent looks pretty deep. I think your approach is good. 26.9 may be too large though.

unterhausen

That bottle cage boss is going to make dent removal difficult
I have a tool that's like a stem wedge that works great. There is nothing wrong with pushing it out, if you can.

Totte86

Sorry, I just remembered I actually measured the seatpost stem and not the seat tube. The seatpost is 27mm and the seat tube inner diameter is around 27.35mm. What size pipe/seat stem would you suggest to use?

When you say "if I can" do you mean cause it will be difficult because of the bottle cage boss or just the size of the dents?

Would I be taking a sizeable risk to the integrity of the seat tube with trying?

Thank you for your input!

Tusk

This may not work, but I would give it a try if it were mine:
Remove the bottle cage bolts. Take an old tube and cut it in half with the cut 10-12 inches away from the valve. Trim the long end of the tube so it will extend past the dent. Tie a knot as close as you can to the valve and on the other end. Partially inflate to give the tube some structure and wrap it in kraft paper to protect it. Insert into the seat tube with the valve as close to the seat tube as possible and inflate. With a small soft faced hammer, lightly tap the edges of the dents. They might come out. They might not.

Rage

I actually just did this on a trick track/fgfs bike. Ran a well greased and rounded at the end rod through there.
Popped the dent right out with just a tiny mark left behind.

It worked pretty well. And was easy peasy 1-2-3. I doubt anyone will even be able to notice after a re-paint.
Same spot, too, but I didn’t have to deal with the bottle cage bosses which helped a lot.

The wedge idea mentioned above sounds like it would work even better, although the proximity of the dent to the bosses complicates this approach as well.

Andrew R Stewart 

One might have to sculpt the end of whatever mandrel/expanding tool to go around the bottle boss best possible.

Not important is how the dent was caused. A U lock? Andy

Totte86

I feel convinced , just ordered the pipe.

I feel almost too ashamed to say but I was attempting to adjust the rear fork cause the frame was slightly out of alignment.
Never done it before and I was way overestimating how tough the seat tube would be to be used as the levering point. I used the sturdiest piece of wood that I had lying around that would be long enough. It didn't occur to me that a *round* piece would just dent the seat tube quite quickly without moving the rear fork all that much.

duanedr 

I have an '80s Columbine that was packaged insufficiently to deal with the rough handling of an airline. The seattube has a similar dent from the rear cogset banging against it as it made a trip many years ago. I considered turning a bar to the required diameter and then cutting a keyway on the mill to clear the bottle bosses. I think putting a brass nose on the bar and rounding it would make sure a sharp edge didn't dig into the dent and cause more deformation. I had also considered filling it with putty and painting it and never speaking about it again. And, proving that actions speak louder than words, I have just ignored it.

curbtender

You might try an automotive paintless dent removal. I've watched those guys get dents out in pretty tight places. Seattube may have enough room to work with.

dabac

But the wall thickness of the average seat tube is a lot more than the skin thickness of the average car door or fender panel.

kraftwerk 

Your idea to fix it sounds interesting....tempting... Let us know how it goes.
I would 'heat' it up a bit w/hot water... makes it more pliable. Double check on that advice.

I have a similar dent in one of my frames, it is very thinned walled tubing.
Showed it to a frame builder and he said best to leave it, since moving the metal again will weaken it. He went on to say:
Metal is a 'crystal structure' & it can't move so many times before failing, like when you bend a paper clip back and forth..eventually on the 3rd or 4th bend, it snaps.

Moe Zhoost

Just thinking about the above quote: If you know a woodworker with a lathe (or maybe you are one), you could use a very hard wood to make a cylinder of the right diameter, drill a hole down the middle, cut it into 2 wedges. Epoxy a nut into the bottom of one wedge, lock the other to a piece of all-thread with 2 nuts, and then after positioning the "tool", tighten the all-thread shaft to expand against the dent. The wood will compress a bit, but that's not a bad thing here.

Bummer. I've done this procedure many times without really thinking about the wood lever and thankfully have avoided damage. Since I always seem to have plenty of scrap 2-by lumber around, that's what I usually grab for.

kraftwerk 

Moe Zhoost I like the cut of your jib. Making a tool for the specific damage sounds like a great idea..

Moe Zhoost

Thanks, though my yawl has no jib. Just the main and a small mizzen.

Totte86

I had a couple of bikes that needed attention first so it took a while to get going on the pipe.

First a mtb from a friend of mine that has quite a bad economic situation and the bike was pretty much ruined in the drivetrain and the in wheel hubs. Did the best I could and I'm sure he will not spend a dime on the bike anyway so no replacing worn out parts. 🎼 Polishing a turd 🎶

Then my older brothers very unmaintained Bianchi. Waiting for a shimano crank and bottom bracket to replace the very nice looking but broken campagnolo setup. What do you call a bike with both campagnolo and shimano parts, shimagnolo? ^^

I did finish the pipe today and also I managed to push out the dents some. There is still some indentation and looking down the inside of the seat tube I can see there are still some small bumps. But its a big improvement. If the pipe would have been a smidge wider or If I could expand it somehow at the right place it could possibly be even better.

These small white cracks, is this just the paint or is this structural damage? :S

bikeforums.net/g/album/23919537

Thanks for all the help!

unterhausen

steel doesn't turn white when you crack it, it's probably the primer

I'll post a picture of my dent outner someday.

Rage

Glad it worked out okay.
And, yeah, looks like primer/paint cracks on there.

Intrigued by this “dent outner” of unterhausen’s.
That and Moe Zhoost’s suggestion both sound like great ideas.

smontanaro 

I realize you've already done your dent repair, but I thought it worthwhile to relate how I tackled a similar problem on a Trek 770 several years ago.

I constructed something like a Cinelli-style wedge expander from a piece of broomstick. I made four crosscuts near the bottom and a hole the length of it. A bit of all-thread and some nuts completed the "tool." It worked well to remove most of the dent. I didn't have a water bottle boss to contend with, but I think you could finesse that by grinding away enough of the broomstick/dowel to clear the boss.

Totte86

I'm actually not quite satisfied with my repair. The dents are still quite visible so I might try something else in the future, the expanding wooden stick sounds promising. If I feel like Im ok messing up the paint I'll also make wooden frame blocks and roll it at the same time as I use an expanding tool inside. There are ridges at the edges of the dents that are wider than the diameter of the pipe, I would like to get rid of those as well so thats why Im thinking frame blocks. If I leave these ridges, would they becomes cracks with a lifetime of use or is it in such a place on the frame that it won't have enough stress on it?