He measured wrong. I had the wheels off my 3500 HO SRW yesterday and measured edge to center. They are 14.09" (358mm), same as every HD ram since 2009. Not 14.37.
IMHO, the dually rotors are probably only larger due to the larger bolt pattern that's due to the large axle tube. The SRW axle tube is necked down to fit the SRW setup. They likely have the same swept area as the slightly smaller rotors, but someone would have to measure hat to rotor edge (I didn't think of that at the time) and do the math.
I went back into my archives when i was able to get with a technician at ram at what criteria had to be met to get the 365mm rear brakes, this is the email.
Rich,
Thank you for contacting FCA US LLC.
VIN: 3C63RRJL9!!!!!!!!
Our records indicate this vehicle was equipped from the factory with the following:
DF2 6-Spd Auto Aisin AS69RC HD Trans
DMF 4.10 Axle Ratio
DRC 12.0 Dual Wheel Rear Axle
ETM 6.7L I6 Cummins HO Turbo Diesel Eng
According to available information, this vehicle should be equipped with the following brake rotor sizes:
Front Brake Rotor Size: 360 x 39.0 mm (14.17 x 1.535 in.)
Rear Brake Rotor Size: 365 x 38 mm (14.37 x 1.50 in)
Sincerely,
Joe
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I honestly wouldn't think that the 410 gear would have anything to do with it over the 373, they both haul a $#/+ load of lbs