Hello this last week i've had a weird noise. The curious thing is that it only sounds in the middle of my commute. It only sounds when I pedal with a certain force and it is like a toc toc toc, the faster I pedal the faster it sounds, and i tell you it is pretty loud. I can also feel it on the pedals, like if ther was a little hammer tocking the rear wheel. Ive checked de breaks, the cassete, chain...The bike has 600 kilometres(370 miles) and I have it since christmas.