Yet another "Mystery Noise" thread

[Turkle]

Hello. So, back in September I was riding in a fast paceline and someone neglected to call out a pothole. I hit that thing going full gas, straight on.

Immediately afterwards, my bike developed a strange noise, and I'm having trouble determining what it might be. I took it to the LBS and they couldn't locate it.

The strange thing is, it doesn't occur when I first start pedaling on the bike. Maybe 15-20 minutes into my ride, it will start. It definitely is part of the pedal stroke, because when I'm coasting, it doesn't make the noise. It happens when I'm pedaling hard enough to be going at least 19-20mph on the flats.

It sounds like a creaky rocking chair, is how I would describe it. You know that kind of crunchy noise an old wooden chair makes? I get a short one of those every pedal stroke. It happens when my right leg (drive side) is just coming through the lowest part of the pedal stroke.

I have checked my wheels, my rotors, and those are all completely true. The noise sounds like it's coming from the bottom bracket area, but I can't be sure as I'm riding fast and I can't get the noise to happen in the stand. It's really hard to try to take a video because it only happens under load when I'm going too fast to comfortably operate my cell phone camera.

Busted bearing in the bottom bracket?? Loose chainring bolt?? The bike is fatally compromised and might explode under me at any moment??? What could it be??

Any ideas on what I should check here??

Thank you!