Rear Brake Shims?

I am putting new rear brake pads on the bike and noticed that I don't have No.9 in the illustration on either side. Are these absolutely needed? They weren't on the bike before and they ran it.

The shims reduce chatter between the piston and the pad, pad and rotor. They are used to lessen the chance of having brake noise particularly in the mornings/cooler temps when the metal is most contracted.

They are there for a reason, however you aren't going to wreck or anything because they are gone. It is pretty common place for people to get aftermarket pads that do not fit witht he shims, so the shims get thrown in the garbage. If you are doing OEM pads, I would replace them, just to know that it is right. If you are using aftermarket pads, check the back of the pad carefully, it may have raised areas, rivets etc that prohibit the shim from fitting anyway.

They are anti squeal shims. The brakes should work fine without them, but may howl as you apply the brake. Worst in cold weather.