I am relatively new to bikes so I am not sure how the tires are supposed to wear. I just replaced my back tire , and just noticed my front tire is showing belt on the left side of the front only. The other side looks to have decent tread left still. I could've swore there was enough lots of tread just a few weeks back. I had the rear installed by the dealer (because I really know dick all so far) but somebody told me there is an alignment to the bike that needs to be adjusted correctly when replacing tires. Is this tire wear normal on just one side?