There is certainly "chatter" when you brake hard on the front and drag the rear brake a touch or dont match RPM to down shift. It could easily be mistaken for a "rattling". Backing it in will cause chatter. Not that he's backing it in anywhere but the same applies in a straight line.

 

i didnt read what everyone else posted but by what u would say i would just advise u not to slam on the rear brake if ur in a panic it will probably just lock up and the back tire will slip out from under u once u try to turn with it locked up, so id probably just say be careful using the rear brake

 

It sounds like your rear tire just lost traction between you slowing down with breaks and downshifting. When I first got my bike I was all excited speeding everywhere...then slowing down really fast. This happened more than once to me while I was downshifting and not matching my RPMs. Did you drop the clutch to engine break? Sometimes if you accidently shift slightly before pulling in the clutch...it may cause your wheel to lose traction. just my 2 cents...

 

Like everyone else practicing braking will help you out. Prob shifting too cause i still think the rattling part was you not catching ur gears correctly.

 

My guess is, like a few others said, you were stuck between gears. I've done it a few times -usually cuzI let the clutch out a little too soon before fully shifting.

In regards to braking techniques: I think the guy is better off stomping on the rear than pulling too hard on the front. In a panic, I will take my chances at sliding the rear versus going over the windscreen then getting run over by my own bike!!!!! My $0.02.