so on my SS bike, the bottom bracket makes a creaking sound (kind of like an old wooden boat) whenever i start pedaling, and continues until i get up to about 15 mph. it seems to only happen when i put force on the left pedal.

i've recently converted this bike to a ss/fixed, andi made sure the chain had absolutely no slack when i installed the wheels. so, should i give the chain some slack? or is something else wrong with bottom bracket?

any help is appreciated, thanks much!