I just got through reading the Insider segment of the November issue where SSBC president Michael Jonas claims that rear disc brakes improve stopping distance 25 to 35 percent over drum brakes. I don't see how that is possible. In this magazine some time ago Tim Moore won a challenge partly by stopping in the shortest distance in a 68 or so Nova equipped with rear drum brakes. Although they were larger units from Master Power Brakes, he stopped shorter than any other car, including a late model Corvette. Please tell me how can Mr. Jonas can justify his claim.  

Discs do provide better stopping power than drums.

Where Michael's coming from, rear discs will help reduce stopping distance, when the bias between the front and rear brakes is set up properly. On stock front disc/rear drum systems, most of your stopping is being handled by the front brakes. When you convert to rear discs, you can adjust the bias so the rear brakes will work more to help stop the car.

Look at road racing. All road racers have four-wheel disc brakes, because they offer superior braking performance over front discs with rear drums.

When Tim Moore won the challenge, how big were his FRONT brakes? Large front discs can be the equivalent of smaller four-wheel discs.  

I dont think discs will stop any better than drums in normal driving. If i am driving and stand on the brakes both will lock up the rear tires. The reason road racers use disc is because they are doing repeated hard braking. The drum will fade more that the disc in repeated hard braking because they wont cool as fast as the disc. If in your normal driving you are having to hit the brakes hard 3 or more times a minute you would benefit from a disc conversion. They way I drive I only hit the brakes hard enough to lock the tires about once a year. I dont drag race so I dont need to stop hard at the end of the strip.  

Thats some great info to know about. One question I have is for a everyday commuter what would last longer. Drums or Discs?