How Powerful the Brakes Really are...

...and the Lexus owner himself said he "had no brakes". I'm not sure how one can separate out "brake damage" that resulted from the brakes being applied, to "brake damage" from a car fire? That said, I'm not believing anything NHTSA has to say at this point. They've had way too many inconsistencies in prior findings, or no findings in some instances, to give me much faith that they know what they're doing.

But sure, if the owner pumped the brakes many times, while trying to stop a high speed run away vehicle, you will get some brake fade damage that results because of excessive frictional heat build-up. Remember, it's all about the heat build-up time that causes the heat related fading damage to the pads. If one applies the brakes in a steady and continuous fashion, the car will come to a stop in a matter of a few seconds and there is not enough time for fading to occur. However, if one pumps the brakes on and off for long periods of time, the heat-build up can cause fading. The pumping action does not allow the brakes enough time to cool, and the brake pad temperature continues to rise as the entire process continues. The sooner, the quicker you bring the car to a stop, the chances are that brake fade will not come into play.

Simplistically - Conservation of energy applies, so the car's kinetic energy is converted into heat (primarily) when braking. Since this is a dynamic system, that is, the velocity is decreasing as you apply the brakes, the total amount of heat that is generated in the braking process is the integral (or summation) of the kinetic energy at any given instanace, over the entire interval of time taken to bring the car to a stop. So, the upshot of this is - the quicker the rate of decerlation, the less total heat that is generated. The easist way to visualize is make a graph. On the vertical axis is KE. On the horizontal axis is time. At zero time you have an initial value for the cars KE. As you apply the brakes, the KE drops and eventually goes to zero as the velocity goes to zero. For the sake of discussion, say the decrease in the KE is linear with time...draw a line that goes from some initial KE to zero in 10 seconds (for example). Now do the same thing, but lets assume the car takes longer to stop, say, 20 seconds. Draw that line. The total amount of heat generated from converting kinetic to thermal energy (heat) is the total area under each curve. You now should be able to visualize that the longer it takes, the more heat build-up you have. While the relationship between heat and the temperature rise at the pads is a complicated formula, suffice it to say that the temperature rise scales with the amount of heat generated. The hotter the pads become, their coeficient of friction is reduced...which, turn, then takes it longer to stop, and thus generating more heat, which raises the temperature even more...and so on.

But my point still remains - Had the brakes been working properly on this Lexus (I don't know that they were?), and had the owner firmly and continually applied the brakes...the car would have stopped. I have zero doubt about that. None. However, you are free to believe what you want. My main point with this thread was to inform some people on this site to the FACT that the brakes are the most powerful system on your car (the caveat is - when working properly).

I guess Prius owners should feel a bit better that we have a "B" setting for the transmission, and is used to help "brake" the car when going down a long inclines, and will minimize the use of your brake pads, and thus avoid the possibility of brake fade caused by excessive frictional heat build-up THAT CAN OCCUR over long decents if one continually applies the brakes.

 

Highly recommend that everyone try this when conditions allow. Not to get over confident by performing such experiements, but everyone should know what their car is capable of doing when all systems are working as designed.

If I were to try this on any of my vehicles, and could not bring it to a dead stop...it would be in the shop the next day, as it would indicate to me the brakes need some attention.

 

"Silly debate"? "Hilarious"? LMAO. Go contribute to such threads as, "what color Prius should I buy?" Or any number of other truely "silly" threads. After all, if you find it so "silly", then don't read. Simple concept.

The discussion has zero to do with blame, or Toyota. Many brands, many makes of automobiles have had reports of unintended acceleration through the years....so this is not unique to toyota, by any means. It's meant to be educational. You would be surprised that most Americans have no idea how to bring their car to a hault in the event of unintended acceleration - no matter who made the car. I aksed 5 co-workers (all male and all college educated) whether they thought their brakes would stop their cars (non-Toyota's) in the event of an open throttle. Only one got the answer right. Americans are simply uninformed when it comes to cars.

Clearly, you missed the entire point of this thread. :noidea:

 

Really, that's all you got? Very informative.

But pretty much as I thought - you got nothing worth saying.

As I said, don't read and move on to other things less "silly"...whatever those might be? I don't know...mmm...maybe you can answer some more "car wash questions". Now that's pretty serious stuff. LMAO.

 

Still does not change the fact that someone in the vehicle said, "have no brakes". The 911 call lasted for approximately 1 minute. IMO, that's adequate time to convey detailed information.

But the fact still remains - Even if the brakes had only been partially working, he should have been able to slow the vehicle to some degree. From all accounts that I have read, the vehicle NEVER slowed, but continued to accelerate. Now that sure seems consistent with the statement, 'have no brakes", now doesn't it?

Anything else?

Who said I didn't read it? Nice assumption, but again, wrong.

It said the rotors from the torn off section look "similar" to those that were in the fire. Note, in making a comparison, he did not say anything about the pads, or the rest of the brake system. He only said, "other rotors (ie those that went through the fire) on the vehicle exhibited similar conditions (to those in the torn out section)". I did not read in this report where he made a similar statement regarding the pads and the rest of the braking system. try reading carefiully before acussing me of anything...JA.

All this aside, I have already conceded that the brake pads can, and will over-heat and ultimately fade, if one brakes hard, lets up, brakes hard and continues this process for some extended period. The brakes do not have enough time to cool in this mode. Read my post about energy and heating, and you might learn something.

So what's your point?

"Concerns brought up before I joined this forum"? Wth. Are you serious.

What other concerns might those be? If you think I read every thread on this site, every post, you are a bigger JA than I thought. Get real, my man. :flame:

This thread, which I started, has to do with the brakes being more powerful than the engine. They are. This is FACT. Not in dispute. But, if the brakes have been compromised in some way, then yes, they will not be as affectinve in stopping the car. In addition, and as I already mentioned multiple times - If one pumps the brakes while trying to stop a run away car, you face the real possibility that the brake pads will over-heat and fade, and will not be able to stop the car. This is not in dispute.

But in the final analysis, since this person was not able to even SLOW the vehicle down (it contiunued to accelerate), it's very clear to this engineer that there was something seriously wrong with his brakes...or something else (unexplained) was happening. Even faded pads will slow the vehicle down to some degree...they may not be able to stop it completely, but the speed will decrease.

That works for me! Really, please don't read.

...and who said that it wasn't?

 

The brakes aside, I'm still amazed that a state trooper, or an individual who should have good familiarity with cars, and someone trained in dealing with panic/pressure situations....did not know how to:

(1) turn the vehicle off

and/ or

(2) put the car in neutral


I realize we all react differently, but IMO, if there was enough time to make a 911 call, and stay on the line for nearly a minute, there should have been enough time for someone with his training and skills, to have found a solution. If this had happened to my mother, my dad...yeah, I can understand they would not know how to handle the situation. This entire thing puzzels me. There are a number of inconsitencies that make me wonder...

 

Now I'm curious, so I went to Google Maps/Strret View to get a better feel for the topography where this incident happened. Unless I am at the wrong location, the terrain near Hwy 125 (turns into Hwy 52?) & Mission Gorge Rd in Santee, Ca is graded, to be sure, but not what i would call very steep (at least from the pictures I see). Further, along his route, there were a number of gradual embankments that he could have turned up and let gravity slow/stop him.

This whole thing smacks of a primetime TV investigation, like 48 Hours. Anybody from SD Union report whether this guy had enemies, or was having marital problems, etc? Hey, I'm not a conspiracy guy, but this sort of stuff does happen... Not saying the Lexus didn't have problems...but there's just a lot of inconsistencies here. Too many systems all would have had to fail for a trained highway patrol officer not to have been able to stop, or at least slow the vehicle down....had he wanted to and the systems had not already been compromised by a 3rd party.

I'm just sayin' it's all rather odd.

 

It's not flat. But the street view images I saw showed that is wasn't that steep, either. i'm guessing, maybe a 5-10% grade? Bay in Santee? I'm from SD, and no bay around there. From the street view of Google earth, I say no water/ponds, either...but then again, I wasn't looking for any water. According to the police report, the car caught on fire, so it couldn't have rolled into water. The car was pretty burnt up.

Anyway, not an investigator, but do enjoy a good mystery.