I feel like a broken record sometimes, but consider an ugly/cheap bicycle if you have to leave it outside a lot in theft prone areas. It can ride every bit as good as a fancy expensive bike without looking the part. Winter road conditions and the nature of daily commuting wreck my commuter bikes enough that I see no point in starting out with something new and shiny, even if they never get stolen.
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.
I actually own a large steel drift that would work. No idea where it came from, but there must be others online in the $10-20 range. You would want to be sure you could draw it out again, so pre-greasing is important.
Bad advice. Bend it once, and it might be ok. Try to bend it twice (back into the original shape) and it will only make things worse, with zero benefit.