Do you use parking brake?

I think he is thinking of cars that have a hand operated parking brake and manual transmission that is used every time you stop on a hill since you don't have three feet to operate the clutch, brake and gas pedal at the same time. Eventually the cable stretches and needs to be adjusted. One question: When we get our 5K or 10K dealer service, will they lubricate the parking brake mechanism?

 

I don't think there's any need, there's nothing readily accessible that needs lube.

 

You have to be very tall to step on it.

 

I've had those on my manual-transmission cars. I don't think I ever had to pull on them hard enough to reach the steel cable's elastic limit; I only pulled hard enough to keep the car from rolling while I worked the clutch.

In my experience, a gradual increase in parking brake travel more often indicates an issue with adjustment of the rear brake clearances than stretch of the cable; get the brakes adjusted right and the parking travel comes right back to the specified number of clicks. Unless you've had Sasquatch yanking on the lever or stomping the pedal.

-Chap

p.s.: interestingly, I had an old Ford that came with built-in Sasquatchproofing. If 'quatch ever stomped on the parking pedal, the "cinch strap" (more like a solid steel rod 5 or 6 mm thick) would just unwrap around the "U" portion. It would leave the parking brake nicely adjusted to proper tension at maximum stomp, and the rest of the cable would be fine, because the tension to unbend the steel "U" was below the elastic limit of the cable.

 

I never once applied it on my 2004 in 13 years and 150,000 miles. The brakes were inspected at 140,000 and had 80% of the original pad remaining.

Fatigue is a normal property of most solids, including metals. It's basically a way of doing statistics about crack propagation (i.e. Miner's rule).

 

I never used the hand-brake for starting on a hill in my manual cars. Not necessary if you learn decent technique. I can start on my driveway (10% grade) while rolling back less than 1/2", zero if I feel it's important.

 

I am thinking about going up a steep, rain slick brick street in Seattle with traffic stopped and an SUV about six inches behind my rear bumper. I may be possible, as you say, but I will admit that I was not clever enough to do it without using the hand brake.

 

I think that the "moosh" is the key here!!
Just moosh it to ratchet up the puppy and set brake. Moosh again to release.
I'll pass it on to my friends with European "caws" so they'll be prepped to moosh when they finally succumb to Prius envy!!

.

 

That's not surprising in light of how the adjusters work; they could still have had the same 80% remaining at 280,000, especially if no helpful shop tech ever had the rears apart at a periodic maintenance and said "weird, these star wheels have never advanced, I'll give 'em a few clicks manually".

Right, if there was anything in controversy here, I don't think it was whether 'fatigue' exists as a concept, but just whether Toyota so under-engineers their parking brakes as to invite fatigue failure under their normal, intended use.

-Chap

 

Both the fronts and rears were at 80%.

I don't buy that their intended use is for parking, despite what the manual says. That's just a bunch of CYA lawyer-speak. You shut the car off and it automatically goes into park. That's how the car is restrained when you aren't moving. The only reason to use the emergency brake for parking is if you are on a steep slope and expect the road to freeze under the tires while you are parked there, and thus want the traction of all four tires restraining the car.

 

Okay, so after some research, the brakes being discussed are "emergency brakes", but they are most commonly used as "parking brakes" because the regular service brakes are so reliable.

How Emergency Brakes Work | HowStuffWorks

"Because most modern braking systems have failsafe measures and warning systems, such as on-dash brake-warning lights and low-fluid sensors, the emergency brake is most often used as a parking brake device. But the e-brake is called an emergency brake for a reason -- using it can save your life."

"The most common use of the emergency brake is as a parking brake. Those who drive manual transmission vehicles, or stick shifts, usually engage the emergency brake every time they exit the car. If not engaged, the car might just roll away all on its own. Automatic transmission drivers tend to use the emergency brake far less, if at all."

"But if you're ever in the highly unlikely but extremely serious situation of having your service brakes fail to function, try to stay calm and pull the emergency brake lever up slow and steady, bringing the vehicle to a longer but more controlled stop."

 

I think there is a problem:

My emergency/parking brake is foot pedal operated, not a "lever." Still it suggests an interesting experiment:

• Achieve a high rate of speed.
• Apply the parking brake hard and steer the car in a new direction.
• Release the parking brake and apply full accelerator.

Bob Wilson

 

I assume that the Prius emergency brake is only effective on two wheels. If I am correct, if, at a high rate of speed you brake two wheels and turn the steering wheel, you can expect to go sideways and off the road or into another car. So what is the purpose of this experiment?

 

'Research' would be so easy if it meant "googling until I find a side-gig-for-freelance-writers web site that bought a piece from a guy named Simon Shadow who seems to agree with me." (Secondary research question: what are the qualifications for a writer to get a side gig with HowStuffWorks?)

There's a lot you can learn about Toyota (and Lexus) brake systems from the Lexus Technical Training coursework on brakes. You can find it on techinfo, of course (sometimes research involves finding info that isn't free, $15 ain't bad), but you don't usually have to because copies of that have shown a tendency to escape onto the web. A google search on the phrase "The parking brake system is a secondary braking system used to hold a parked car in position" is specific enough to find escaped copies of that book, without finding a lot of other unrelated things. (The quoted passage goes on to say "Since there is no inertia to overcome, less braking power is required to hold the vehicle stationary and less force is required to apply. The application of only two of the four brake assemblies are required to hold the vehicle.") The authors of that didn't get a check from HowStuffWorks, but then they did work for Toyota and demonstrate deep knowledge of their brake system details.

Wikipedia is another place to look; it is community written and edited, with editorial policies that are clearly stated, and you can even follow the history of the article's coverage of the terminology question.

But as long as Simon Shadow's HowStuffWorks article is on the table (whoever he is, at least he knows Shakespeare), why not explore a little more of it?

(here Simon is relying on wiseGEEK).

Simon also mentioned the existence of pushbutton electric versions (my mom has one, in her Volt):

(He got that information from an article written by Paul Zangari for Motor Age.) It would be fun to research how to use that to stop a moving car without loss of control—assuming the electric system will even apply it with the car in motion.

And, to his credit, Simon did track down the actual requirement for the secondary system to be there at all, correctly, to the federal motor vehicle safety standard FMVSS 105 (which calls it a parking brake).

You can scroll down to section S5.2 to see what the performance requirements for the Parking Brake System are. (In brief, hold a passenger car stationary for 5 minutes, subject to tire traction, forward and backward on a 30% grade—relaxed to 20% if it is used together with a parking pawl that won't break in a 2½ mph front or rear impact.)

So, you can get a lot of good information even from the source you selected; Simon's persistence with the term "emergency brake" seems to be the only part he argues contrary to his sources and support.

-Chap

 

Actually, I read the federal regulations first, and then found a summary article about it that's easier to read.

 

"Easier" in the sense of agreeing with your claim about terminology, since the federal regulations actually didn't?

-Chap

 

No, the regulations are hard to read because they are in many pieces and the vehicle types are mixed together (light, truck, trailer) in the regulations. That makes them hard to read. They do agree with both what I said and what the article said.

 

You mean except for the fact that they consistently use the term "parking brake", and specify its performance at holding a stationary vehicle on a grade, contrary to both what you said and what Simon's article said?

Dude. PriusChat is a pretty great community. Generally interested in getting to the truth of technical matters about our cars, and pretty friendly about it most of the time, but what do you take us for? I did include a link to the FMVSS upthread, so your latest claim here is tantamount to betting that nobody else on PC can click a link and read.

-Chap

 

Did you read the NHTS comments about that? The updates later for heavy vehicles? Yes, the government calls these things "parking brakes" but they are primarily on the vehicles, and arranged the way they are (mechanical only) specifically to work when the hydraulic braking system fails.

Request Rejected

"Why use a cable arrangement? The emergency or parking brake system is completely mechanical and, by design, effectively bypasses the entire hydraulic system. In the event of a total brake failure (for example, a ruptured hydraulic line), the car or truck can still be brought to a safe stop."

That's the reality of the brakes. They can also be used to prevent roll-aways in highly unusual situations, but the main reason they are on the car is to give the drive the ability to stop the car if the hydraulic brakes fail.

Parking brake - Wikipedia

"The hand brake was originally intended for use in case of mechanical failure where the regular footbrake was inoperable or compromised (hence the emergency brake name)."

The last time I used a parking brake when I was stopped somewhere other than my steep driveway was right around 1990. This is because there's generally no need since most parking surfaces are flat and either leaving a manual transmission car in first gear or an automatic in park is more than sufficient to prevent rollaway accidents.

On the other hand, a friend of mine used his hand-brake to save his life (or at least a major crash) when his service braking system completely failed. Further, we were both taught and tested in driver's education on the use of the mechanical brake for this purpose.

 

The other thing we were taught in driver's ed was not to get used to using the emergency brake when we were parked. This is because we get a lot of rain and snow in Colorado when the temperature is right around freezing. This can cause such a brake to freeze in the locked position thus disabling the car. I've seen this happen to other drivers on several occasions. The thought was, if you get used to using it all summer, it will be hard to break the habit in the winter, so it's better to not get in the habit at all.