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Comparing Free Backing and Duo Servo Hydraulic Brake Assemblies


whats better free backing or regular?Also if you have free backing and trailer unfortunately happens to disengage with the brakes activate by the break away?


Expert Reply:

Good questions. The difference between free backing brakes like the # AKFBBRK-35-D and regular hydraulic drum brakes like # DMSB18794M-93M (referred to as duo or duel servo) is that the wheel brake cylinder has pistons on both sides of the regular/duo servo brakes instead of just the one side on the single servo free backing assemblies. The amount of braking doesn't change much between them, they just function differently yet under the same amount of hydraulic pressure. The duo servo will give more of a even pressure to both shoes, but both types will apply appropriate braking/stopping pressure.

If you will be using reverse with a surge brake actuator, most people prefer the free-backing because they don't need to add the reverse wire function or hit the manual lockout to back up. With electrical going to an EOH system or a brake actuator with electric lockout solenoid, the free backing aren't needed but also aren't a problem.

Both types of brake assemblies will engage the brakes when a breakaway is activated. You will want to make sure you get the correct size brake assemblies for your hubs and this is easy to do by measuring the back plate on your current brake assembly or the inside diameter of your hubs.

I've attached a link to each type of assembly for you to see your options. Let me know if you have further questions.

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