My bike ('83 Bianchi Nuovo converted into a fixed gear) has been making an ominous creaking noise on the downstroke of both sides. It's been getting progressively worse and I think I've felt something slip a couple of times (though I can't be 100% sure about the slip).
It's a really low pitched creak and it's definitely coming from that bottom portion of the frame. I've popped my chainring off, adjusted the chainline and put it back on. This seems to reduce the noise for a while, but then it just picks right back up after 10-15 miles. None of my chainring bolts are loose at this point. I've also re-tightened my pedals, thinking that might be related.
My bottom bracket probably hasn't been taken apart since the bike was put together initially and it doesn't sound too great (gritty, needs lube) if you spin it without the chain attached, but it spins just fine. I've not been able to remove the bottom bracket in the past, so I may just need to break down and take it to the coop and use a vice.
Anyone have any thoughts as to what might be creaking? This is my primary means of transportation and I'm afraid that something is going to snap at some point and I'll end up a stain on the road.