Rattling coming from rear with street wheels

Hey guys, I rode with the street setup for the first time over the weekend. I noticed a good bit of a rattling noise coming from the rear. Any idea what it's from and how to reduce it?

Could it be the spacer in the wheels? The motor? Any tips would be appreciated.

 

Most likely the motor covers, my Carbon GT does the same thing and annoys the hell out of me. Its only quiet on smooth pavement.

 

We have an ongoing thread about this already guys here: Snake 'Rattle' and Roll

 

My Bamboo GT did the same thing, until I switched to AT wheels