Nick:
All 300/300K except ram came standard with 11x2.5 rear brakes with standard suspension. Standard suspension had 5-leaf rear springs and no front sway bar. Heavy duty suspension was optional on all 300/300K and standard on ram cars. The heavy duty suspension included 11x3 rear brakes, 7-lear rear springs and front sway bar. On a side note, heavy duty suspension was not available on Newport/New Yorker.
On a car with 11x3 rear brakes, the backing plates have a 1/2 inch offset towards the centerline of the car, use the same 11x3 shoes and used on the front. The drum is deeper and has an interior machined surface that is 3.5 inches deep. The standard 11x2.5 drums have a machined surface only 3 inches deep. That's how you tell the difference between the two drums.
Some people who don's know better have installed 11x2.5 brake shoes into an 11x3 brake system. When this is done, the inside edge of the brake lining protrudes 1/4 inch outside the drum when installed. I know this because someone installed 11x2.5 linings in my K with 11x3 inch rear brakes.
Chris the KMANIAC
-----Original Message-----
From: Nick Taylor <nicksgaragesd@xxxxxxxxx>
To: Chrysler 300 Club International <chrysler-300-club-international@xxxxxxxxxxxxxxxx>
Sent: Fri, Sep 9, 2022 7:36 pm
Subject: {Chrysler 300} 300K Rear Brake Size