AP Racing BBK front rotor bell to rotor noise

[1DarkChaos]

Hey guys
Not sure how to explain this but im running out of ideas
The front rotor is making metal to metal sound when going over bumps. Upon inspection, between the bell and the rotor there is a little gap (due to it having shims). I thought it was installed wrong but it is correct, and I also tightened the screws and still no fix.

Is this normal?
If anyone can chime in that would be awesome
The design.of the rotor is here, any help.would be awesome
Thank you!
https://www.apracing.com/drawings/P12.283.Iss.2pdf.pdf

[M3SQRD]

Are you sure it's not the pads moving inside the caliper?

[dparm]

jritt@essex might be able to shed some light.

[1DarkChaos]

no its not the pads banging on the rotor or caliper. i had the caliper removed with the rotor bolted on, when i hit the rotor, it still makes that metal on metal sound.

[roastbeef]

Maybe some of your hardware is loose and the disk is sliding on the hat too freely?

[1DarkChaos]

thats what i thought initially but 100% its not loose. do anyone have this same rotor? with the 3 shims between the hat and the rotor?

[SpartaEvolution]

How many miles have you put on these rotors? What number in the drawing are you referring to about the shims? Is this happening on both rotors or just one?

Two-piece floating rotors have a little spacing between the rotor and hat to account for the different thermal expansion rates of the two materials. Typically, belleville washers are used to allow this spacing but prevent excessive movement / noise, but if the rotor/hardware is getting old, extreme heat cycling can cause the washers take 'set', which will allow movement. After speaking to my rotor engineer, he doesn't want to comment on potential failure modes for these specific rotor/hat designs, as he has not had a chance to inspect/test them in person, but he recommended re-torquing all your rotor bolts (~10 ft/lb according to the .pdf you linked), which it sounds like you have already done.

If these rotors are new and you've experienced this noise since install, you might just have to live with it. If they are old, you might need to replace the rotor ring or hardware. Either way, I would recommend getting in touch with AP.

[M3 Number 86]

you might have a full floating caliper system. go to 2:50

[M3SQRD]

Originally Posted by M3 Number 86

you might have a full floating caliper system.

This kit uses a strap-drive system to mount the rotor to the hat so it’s not a true floating rotor design. The straps have to rotate to allow relative motion between the rotor and hat.

[M3 Number 86]

Originally Posted by M3SQRD

This kit uses a strap-drive system to mount the rotor to the hat so it’s not a true floating rotor design. The straps have to rotate to allow relative motion between the rotor and hat.

In the diagram it doesn't look that way. I thought only Pfc uses the strap style connection?

[1DarkChaos]

i studied the design and it seem like its the nature of the design. The sound is just like the youtube video posted. Man i guess i have to get used to it, im just not sure if the instructor will feel comfortable riding in my car with the sound.

[M3SQRD]

Originally Posted by M3 Number 86

In the diagram it doesn't look that way. I thought only Pfc uses the strap style connection?

Item #16 on the drawing are the straps (links) that go between the rotor and hat. No bobbins are used in this AP design. This is different from PFC’s design.

[Ervin87]

I have this kit, and I don't have any noise going over bumps. I do have what sounds like metal to metal noise when driving at really low speeds (less than 3mph), but that is the pad against the rotor. It can be annoying, and loud at time. Softer pads and new pad retraction pins helped quite a bit.

[mlhj83]

Originally Posted by 1DarkChaos

Hey guys
Not sure how to explain this but im running out of ideas
The front rotor is making metal to metal sound when going over bumps. Upon inspection, between the bell and the rotor there is a little gap (due to it having shims). I thought it was installed wrong but it is correct, and I also tightened the screws and still no fix.

Is this normal?
If anyone can chime in that would be awesome
The design.of the rotor is here, any help.would be awesome
Thank you!
https://www.apracing.com/drawings/P12.283.Iss.2pdf.pdf

I have the full AP BBK, and understand the entire system. There should be nothing there that is loose enough to make that much metallic knocking as you describe. There is sufficient rigidity in the strap drive floating mechanism to prevent excessive axial and radial movement. Excessive radial and axial movement of the rotor will result in the rotor hitting the hat/bell with sufficient force to create the knocking noise. Are you sure the strap drive bolt, disc mounting bolt, and the associated washers, nuts etc, are all in their intended positions? Is the anti rattle pad clip installed correctly to prevent the pads from rattling?

If you aren't able to inspect and perform measurements to identify the problem, have your install inspected professionally by a proper racing garage that understands these setups.