creaking sound
 

So my bike started creaking, I'm guessing it's somewhere around the bottom bracket.
I did a one leg drill just to identify the culprit and somehow the noise only started when I pedal with my left leg.
It has a constant ticking/creaking sound when the pedal is on a certain position.
I've twice changed the GXP threaded BB to a new one and yet it's still creaking.
I've swapped the QR, pedal, cleat, saddle, seatpost from my other bike, and it still making the same noise.

I'm using a steel frame that I bought around 2012, it never crashed, so I'm kinda hoping it's not the frame.
I've built around 3 bikes so I kinda know my way around it but this one frustrates me. Any symptoms that I might have missed?

My bike started creaking when I got it back from a tune up. Same problem as yours. It seems to be an epidemic. Left side, out of the saddle. I thought mine might be coming from the fork, headset, wheel(?). You can't ever tell.

Chainring bolts?

I chased a creak that sounded like it was coming from the crank area and it turned out to be the the "saddle tuner" in the nose of my Fizik Kurve. It's hard to chase there noises down as you've already replaced most of the likely causes. Good luck.

It's possible that the noise is because of assembly and not from a bad component. This would explain why repeated replacement doesn't fix the problem. Is the OP using good assembly practices? Lube between threaded fittings? Proper tightening torque? Proper checking and possible correction of factory assembled components?

There are many times when a creak has been fixed with proper removal and reinstall of the same component but now using good assembly methods. Remember any contact between two parts can be the cause of creaks. Chainring bolts, pedal cages onto their body, cleat clasping parts onto pedal bodies being some that many don't look at or take cars of. Andy.

I get this creaking a lot myself as well. For me its usually after I ride the bike in the rain once or twice. It usually means that you need to pull out the bottom bracket, clean and reinstall it. I also had to do the same for the seatpost. I don't have fenders, so a fair amount of road grime from wet roads can go up into the seatpost binding bolts. I have stopped the old school mentality of "grease all of the bolts/threads". That can hurt in some situations that really need light thread lock. For example, I greased the 8mm bolt on older Shimano Octalink V1 cranks. I ended up stripping the right crank arm a bit since the bolt came loose a few times. So should have cleaned and just used thread lock on that bolt. Lesson learned...

last year I had a creak I just couldn't locate, eventually turned out to be the headset. Clean/lube took care of it. Had another tough one to find here a couple weeks ago. It sounded like the BB which I had just replaced, and occurred only out of the saddle. Turned out to be the back wheel skewer was not tight enough.