Hey guys, I'm pretty new to biking so i'm not sure if this is something simple or more complex. When I ride there's a kind of scraping noise of some sort. Something is definitely rubbing on something and it causes me to slow down and stop moving. I noticed it happens when I have to ride uphill, and sometimes after I stop and have to start up again. When i flip my bike over and run the pedals everything seems fine, so kind of clueless here. I'd appreciate any help.