Bicycle Mechanics - Is my frame cracked?

Did a pretty hard ride on my 16 year old mtb (steel frame) earlier last week...probably the hardest I have ridden it in years. A couple of days later, I take the same bike out on the road for some steep road climbs. On the climbs, as I'm really pushing the pedals and putting pressure on the handlebars, I hear a random creaking noise coming from somewhere on the bike. For some reason, I decided to grab the top tube...and the noise stops. I can feel the top tube shaking as I ride, and when I let go, the creaking noise comes back.

Is my top tube cracked? I looked it over and see a place that looks simply like a scratch in the paint, but I suppose could be a crack...

Probably not cracked. There are lots of reasons for a bike to creak. Pedals that need to be tightened on the crank, headsets, seat posts, bottom brackets... Tighten all bolts and adjust all bearings to make sure nothing is loose as a start.

How's the audio world going? I haven't been involved much lately.

hey zacster!

I checked the headset and fork, and both appear to be as they should be. Bike had a full tune-up about 3 months ago, so I'd be surprised if it was anything else. The fact that the creaking stops when I grab the top-tube firmly (and the fact that I can feel it vibrating/shaking) is what makes me think it is cracked (can't imagine that grabbing the top tube would stop a creak caused by a loose bottom bracket)...

Audio has been slow...might get out of the biz soon. Am very satisfied with my system these days, tho!

Ah, full tune up. That's the death of any bike :) You are probably dampening the creak when you grab the top tube. Try some of Herbie's tube dampers on it! Creaks are the hardest things to diagnose, as they usually only happen under load.

I haven't turned on my tube amp all summer, the last thing I want is something running at 200 degrees in my living room in this heat.