: 86' FWB 307 - Brake Drum Size??

03-27-11, 11:00 PM
I'm getting ready to take my 86 FWB (307) in to have all 4 of my shocks replaced (Fronts: ACDelco 530-9; Rears: ACDelco 504-511). I figured since the tires are going to be off that I might as well get some work done on my rear brakes.

I'm planning on purchasing new wheel cylinders and brake shoes for both rear ends. But they offer two sizes for my car, an 11inch and a 12inch...

Is there a way to tell which size drum I have currently on my car without taking more than the tires off?

Also just the make sure I'm getting it right.., if the drum is 11 inches, then it can only have an 11 inch wheel cylinder and 11 inch shoe correct?...and respectively with a 12inch drum (12" cylinder/shoe)?


03-28-11, 01:50 AM
My understanding is that certain Cadillacs of that year had beefier suspension and brakes if it had the "VIN 9" motor versus the standard "VIN Y" motor. Those were the trailering package and commercial service cars. I'm not certain, but I would reason the standard is the 11" and the VIN 9 has the 12" drums.

To see which your car is, check the vin number. I believe the 8th character is the Y/9 position. The dealer would be able to tell you all of this for certain.

Best of luck,

03-29-11, 04:27 PM
Thanks for the reply My_favorite_Brougham.
I just checked, and I do have the more common vin Y model.

Anyone have a recommendations on the rear brakes, if I should get stock AC Delcos or if anyother brand would do just fine?

I guess I should take off one of the rear tires to check, but does anyone know if it'll show the brake size (11" or 12") imprinted somewhere on the outer rim of the drum?

cadillac kevin
03-29-11, 06:59 PM
I had AC DELCO parts installed when I had my drums overhauled. the car stops quick, firm, level, and in a straight line. I can't complain. I think my drums are 11's.