In the stable there resides an '04 Oldsmobile Bravada and '12 Mazda CX9. After having new pads and rotors installed on the CX9 recently, I've noticed an appreciable difference in the front/rear rotor diameters (larger in the rear). So, I eyeballed the Bravada and sure enough the same setup exists there also. What braking engineering dynamic am I witnessing , always of the mindset that the BIG ones went up front. Does anti-lock(vehicle weight) contribute to this arrangement?
TL;dr: it depends.
Long answer: Brake output is a function of piston area, distance from piston center to hub center, pad friction behavior across operating range, and available hydraulic pressure.
brakes convert kinetic energy to heat. The rotor temporarily stores most of that heat, and transfers that heat to the atmosphere as a function of airflow and temperature difference between the rotor and the atmosphere.
the performance targets for a specific application will drive the range of components from which a system can be configured. selection of specific components for an application is influenced by availability, cost, manufacturability, ease of assembly, serviceability, and durability (warranty).
I'll stop there.
Do they have internal drum parking brakes? I imagine a tiny caliper with a larger rotor would give similar braking torque to a larger caliper with smaller diameter rotor. But with the internal drum design you have to have a larger rotor to fit over it. Couple that with the lack of need for big front brakes and you might see that disparity.
Just a wildassguess.
Also, if they have small drums in the rear for the emergency brake, the rotors can be larger in diameter to accommodate this.
Vehicles with RWD/AWD and traction control/e-diffs can also use larger rotors due to the extra load placed on the system.
Could also be parts bin engineering. We have this rotor that fits this hub, and this caliper.
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