So, you're building a hot-rod with a Mustang II front end, or you're trying to maintain your awesome, quirky Mustang II or Pinto, and you get around to changing the Front brakes.
When you have the rotors off, the Parts monkey will ask you which rear end you have in your car. 6-3/4" or 8". This is an ERROR in their listing for inner wheel bearings.
Regardless of their suggestions or advice use the BR13 and BR12 bearings - Not the B5 bearing. here's why.
All rotors are listed as D4FZ 1102-A. This is the only rotor listed by Ford in their 73-79 Ford Passenger Car parts book)
All 74-78 Mustang/Mustang II (F) and all 74-79 Pinto (L) use rotor D4FZ 1102-A see the black triangle note in the book? This means the bearing cups installed on the rotor are D0AZ 1202-A and D0AZ 1217-A.
Flip the parts book back to the bearings..
So, the error clearly started somewhere in the Ford Motor company.
A quick bit of Google-Fu shows you pictures like these.
OUTER BEARING: D0AZ 1217-A : LM-12700 and LM-12710 use with 7/8 ID bearing.
This Outer bearing cup LM12710 is used with bearing cone LM12710 to make up BR12.
This Outer bearing cup has an OD of 1.781
INNER BEARING D0AZ 1202-A : RB D0AZ 1202-B LM68110
This Inner bearing cup L68110 is used with bearing cone L68149 to make up BR13.
This Inner bearing cup has an OD of 2.328
The ID of the BR13 bearing assembly is 1.377"
Here's the punch line:
BR5 has an OD of 2.563" - IT WILL NOT FIT THE PINTO/MUSTANG II ROTOR
BR5 has an ID of 1.375" - it is too small to fit the mustang II spindle.
Check this with a 2" micrometer.
So, maybe there is a fictional rotor that existed that was replaced by our rotor D4FZ 1102-A
well... fortunately for me I found the 'Change up book' online
So, that seems to be the only rotor.
I believe the origin of the error comes from misreading a spindle change date..
The date in the parts book for the spindle change for the Mustang II is 6/3/74 which, may have been misread in another department as 6-3/4. There is only ONE version of front wheel spindle used from 6/3/74 (JUNE 3, 1974) until the end of 1978 production. They carry part numbers D5FZ 3105-A (RH : ID#D52W 3107-AA) and D5FZ 3106-A (LH : ID#D52W 3108-AA) There is no evidence of a different spindle or light duty spindle with a different ID on it's inner wheel bearing.
If you happen to have a Mustang II or Pinto Rotor that has the BR5 Inner Bearing. Or if the early spindle Measures under 1.375 (sliding fit) please take pics and show me.
My journey is one of information and if I am in error, I would like to be informed of it as such and to make changes to my post accordingly.