I picked up my beautiful black Prius yesterday and am overloaded with new information on how to drive and operate all the features. One instruction keeps popping up and that is to set the emergency brake each time you stop and are finished driving. What is the purpose of that? I have never done that before on any car. I just put it in Park and leave.


Allen.

Its better for the park gear, and in the odd chance it fails the car isnt going anywere

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You should ALWAYS set the parking (emergency) brake!
There are two reasons:
1 - the park claw does not always fully engage, if the car is on level ground or not moving. Then, if something begins to move the car rapidly, it can skip over the retention holes for the claw and just keep on moving. Then, if the car does damage, you will be responsible if the parking brake was not set. This may sound silly, but has happened not that infrequently.
2 - on many cars that have drum brakes (including sadly the North American version of the Prius, in the rear) these brakes are self-adjusting through the parking brake action. Every time you set the parking brake, the pads are adjusted. If you fail to do that, the brakes pads will wear (they alwasy do) and brake pedal travel will increase.

Good information on claw not always engaging. As to rear drums, what I understand happens is that as the brakes shoes wear, they become farther from the drum so that eventually, they do not make contact. The emergency brake setting keeps that distance adjusted. I experienced this on my other car, a Dodge van RV conversion. I never set the brake and when inspected, the rear wheel turned freely as the shoes were not making contact with the drum. After a manual adjustment, the emergency pedal was higher and braking was better. I was hoping that the Prius would work differently but I guess not so I will set the E brake from now on.

I don't know if things have changed from when I studied mechanics, but from what I learned the rear drum brakes are actually (or used to be) adjusted when you apply the normal brakes going in reverse at a reasonable speed. This was the procedure for adjusting new brakes on cars that didn't allow you to get at the adjustment sprocket. The Prius may be different because the mechanical brakes are heavily subsidized by the regenerative brakes.

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That's what I thought too which is why I never set the E brake. I found out differently when I had them checked on my van during a recent trip through BC at Canadian Tires. Because of the design of the van, they had to pull the rear wheel/axle assemble to do this, so they said. Cost around $100. Thanks for feedback.
Allen

Schwa, in the US NHW11 Prius (2001 model year in my case), drum brake adjustment is just as you describe. Indeed with the brake drums off everything looks entirely conventional in there.

An owner of the NHW20 (new model) has told me that the parking brake/emergency brake in that model uses a second set of brake shoes. I am not sure whether this is actually the case.

European Prius (some or all) have rear disk brakes, so it is a different beast.

DAS