Originally Posted by
habilis
Yet another option: If you can find a steel pipe or rod of a diameter close to the inside diameter of the seat tube, you could pre-lube it and gently tap it down to where the dent is. Carefully push out the dent and check for cracks. If the tube is slightly bent, this method could even straighten it. You have little to lose. Aluminum is more malleable than some people think.
Or the lower half of a long aluminium seatpost. Pound it in, and leave it. Of course, if you don't get it positioned right, you might not get it out again and might make the frame unusable. If you could get it in (maybe lube with epoxy???) then it could permanently reinforce the frame. Perhaps first use a long steel rod to reshape the frame, then pound and epoxy the seatpost in place.
Originally Posted by
rrkm
A thief... managed to bend the seat tube on the aluminium frame.
Originally Posted by
asmac
Which frame tubes are most critical for failure or likely to fail catastrophically?
I ask because I have a steel frame with a dent in the middle of the downtube along its length (1-1/2" long, maybe 1/8" deep) caused when my car was rear-ended and the bike was pushed into the bike rack.
Originally Posted by
FBinNY
This is a steel frame, with an impact dent in one of the least consequential places possible.
Were you responding to the OP's question (aluminum frame), or
asmac's question (steel frame)?
Different tubes, different materials.
In
asmac's case, the downtube is under tension (some framebuilders simply use a cable rather than a tube), although it will experience some lateral torsion. Assuming a rather mild dent, and not bent tube, then
FBinNY's advice to leave alone would be appropriate. Perhaps check the frame alignment before investing a lot of money in the project.