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NY State inspection guidelines call for a parking brake test similar to this: "Car must hold in Drive under moderate acceleration. Parking brake must lock in place and be released independently from service brake" An auto release parking brake is given a cursory hardware check (nothing seized) but not tested in motion.

Many of the quick lube places that do inspection here interpret moderate acceleration as a 1500 RPM. They aren't really able to do any repairs so they look for a reason to fail people. I guess if you have a smaller engine with rear drum brakes that should be no problem.

I have a V8 car with rear disc brakes (caliper parking brakes) and it usually fails there (but has no problem passing at a Ford Dealer). The dealer said moderate acceleration is a tap of the gas pedal and the quick lube places are wrong. I used to be a mechanic and I agree. Even with new pads and cables the car creeps at 1500RPM. The parking brake will definitely stop the car but not lock the wheels.

Is a parking brake supposed to hold at such a high RPM?

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There are two kinds of friction, static and dynamic (kinetic). Static is always higher than dynamic, and I think that's why you can't test the brakes at a sustained higher RPM, as once you passed the static point, it drops a bit. This makes the car easier to move under load. So your assessment is right, and a sustained 1500 RPM will likely get your car moving. We used to inspect them for tightness, and to ensure like you said, a slight increase and release.

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    Bob are you a pilot? I have a similar headset, but I was a maintainer in a previous life.
    – FossilizedCarlos
    Commented Dec 10, 2011 at 3:40
  • no, I was riding in the port-side gunner seat on that trip. Those headsets are tremendous, though.
    – Bob Cross ♦
    Commented Dec 10, 2011 at 6:58
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The quick lube place isn't thinking quite right. 1500 RPM means different amounts of power with different engines.

Most American V8 engines tend to have a lot of low-end torque. On my 2.5L V4 car, cruising speed is ~2,700 RPM. On a former 5.7L V8 pickup, it was 1500 rpm -- enough power to move a loaded truck and 16 foot trailer at highway speed. Parking brake at 1500 RPM? I'd bet it wouldn't hold that kind of power even if it were new.

RPM to power output is very engine dependent. If you've got a V8 Ford, it probably has rear wheel drive. Your brakes don't stand a chance of ever holding back the throttle.

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  • Thanks for the answer, yes its a RWD V8 Thunderbird.
    – Len
    Commented Dec 14, 2011 at 1:11

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