I've experienced complete loss of brakes with a single circuit MC, it is no fun at all. A rear drum broke off and wobbled around which allowed the wheel cylinder to blow out. Really didn't even start as a hydraulic problem, sure ended with one though.

If there is even a slight chance that a dual circuit MC can reduce the pucker factor it has to be worth it.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-