Argonaut

2 piece rotors are composed of the "hat" the center part that mounts to the hub and the "ring" which is the friction surface. So yes, it is the outer part.

Lil_Chef

is it smart to replace only 1 ring? i guess it shouldnt matter much since they are relatively new...but they have been resurfaced...

even so i still dont think that will address the fact that the pads are really loose. i guess only time can tell.

Argonaut

Chef - I have some more info here that might be of help to you:

I have mentioned in a few posts that I installed a set of 4-piston, radial mount, AP Racing calipers with full floating, 2-piece rotors recently. I haven't used them much and am still getting a feel for them. This past weekend I took the car for a couple long drives thru the country side. As best I can tell, I have the same issue you are describing. Specifically the brakes are noisy, as in NVH type noise. For example - when moving slowly across a parking lot or when leaving a stop sign I can here a 'knock, knock, knock' sound (not when the brake is pressed...rather when the brake pedal is not being pressed and the car moving). I have since talked with a couple of experts on this, one of them being a guy who builds race car brake systems for a living. What they are telling me is - this is completely normal. My rotors have J-hook slots in them and whats happening is the pads are catching on the slots and jiggling around. As mentioned, the rotors are full floating, this means I can reach my hand thru the spokes of the wheel, grab the rotor and jiggle it, by design. So the combo of the slots and floating rotors allows this to happen. One temporary solution that was suggested is to put a chamfer on the edge of the pads so that they don't get grabbed by the slots.

You have two piece rotors but haven't said if they are a floating design or not. At any rate, you should try this chamfer idea and see if the noise goes away. Let me know what you find.

Lil_Chef

well i will first just install the new rotor ring whenever that comes in and i get the free time. i suspect my front passenger rotor has "re-warped" because when rotating the wheel while it is in the air there is a section on the rotor that catches so badly it actually requires effort to spin it. The pad may be catching on the high spot, causing it to make the knocking noise.

however i will definitely try out your suggestion if the new ring doesnt work. thanks.

Lil_Chef

Problem solved! i got my new rotor ring on and ready just in time for the track weekend. my old ring looked like utter crap. you could visually see the unevenness in the width of the ring.
i now have the new ring on and the pad is no longer moving within the caliper (audibly at least).