Quote:
Originally Posted by leegreen
So what is the difference between a parking brake and an emergency brake and how could you justify not having an emergency brake?
'never needed one so far' would be a weak justification for omitting a safety feature every vehicle built since the '30s has had.
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That's a
great question. It's been that way since at least 1981.
https://www.ecfr.gov/current/title-4...ection-571.105
FMVSS105 describes braking standards for most road vehicles. Most of the rules are built around stopping a vehicle within a given weight class, travelling at a specific speed, within a specific distance. S5.2 is titled "Parking Brake" and it's slightly different than the service brake standard. For most of us, the park brake standard is this: "Except as provided in § 5.2.2, the parking brake system on a passenger car and on a school bus with a GVWR of 10,000 pounds or less shall be capable of holding the vehicle stationary (to the limit of traction on the braked wheels) for 5 minutes in both a forward and reverse direction on a 30 percent grade." Vehicles less than 10,000 lbs are considered passenger cars.
For 11 months in 1981 the grade was decreased from 30% to 20%, but in December '81 the grade was changed back to 30%.
In a document dated 6-30-05 a representative of the NHTSA speaking in regard to changes to FMVSS105 stated "...the service brake system is required to function with a variety of failed components. The parking brake system on hydraulically-braked vehicles has never been required to provide an emergency brake function." I have not yet researched the accuracy of this claim, but here's the document with the claim.
https://www.federalregister.gov/docu...-brake-systems
I grew up with vehicles equipped with an "emergency brake" and I was taught to always think about how I would apply that brake if I needed it. I also think about how changing my rear brakes on my '99 Suburban to disc would reduce the effectiveness of the park brake when loading a car trailer. With the experience I have with inoperative and minimally effective rear disc/drum park brakes, I have to vote for larger drums on the 'Burban instead of discs.