smaller piston is 6.777 square inch
larger piston is 7.284 square inch
The ratio is 0.866
How are you going to be using the truck? If it is unloaded most of the time I'd say go with the smaller caliper. In a panic braking situation if the rear brakes apply too hard, the rear end will come around. That's why the first ABS in trucks was on the rear axle.
What do newer trucks with your configuration use on their rear disk brakes? Figure out the area of the piston(s).
R.
I'm tired of the rear brakes locking up when it rains. Even though this truck has RWAL the shoes, cylinders and drums need to be replaced. It's a real PITA on these trucks to do that work and it doesn't make sense not to upgrade to the discs when the cost and work involved is pretty close.
So yeah, it's empty or loaded light 90% of the time. I've heard from others that used the larger piston caliper and they say the RWAL works fine with it. Still I'm over sliding down the highway sideways in the rain.
I have no access to a newer truck so I can't compare.
