My bike is a 2004 Trek 5200. Full Ultegra, double crankset up front.
I have a moderate "creaking" noise that sounds to me like it's coming from the bottom bracket. Seems to only happen on the upstroke of the left pedal, whether mashing or just riding. I've done the troubleshooting stuff listed on the Park Tools website (check crank arms, chainrings, pedals), but it's still noisy.
Could this be/is it the bottom bracket itself going bad?
I bought the bike used from feeBay, and know nothing of its history...
Please and thanks!