Brakes unable to stop runaway Lexus in California?
in [Toyota]
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From: Ray O on 16 Nov 2009 16:28 "hls" <hls(a)nospam.nix> wrote in message news:sJWdnfF9FOHXI5zWnZ2dnUVZ_oKdnZ2d(a)giganews.com... > > "Ray O" <rokigawa(a)NOSPAMtristarassociates.com> wrote in message Before > power assisted brakes were introduced, people >> routinely stopped vehicles by stepping hard on the brake pedal. > > That is true, Ray, but also in those days we had front and rear drums, for > the most part. > Discs required a lot more pressure than drums, hence the power assist > brakes became > a necessity rather than just a luxury convenience. > > Among other things, pedal effort is a function of the design of the master cylinder, difference in size between the master cylinder and wheel cylinders (disc or drum), and pedal travel distance. The larger surface area of the piston in a disc brake caliper relative to the surface area of the piston in the master cylinder gives a mechanical advantage over the smaller surface area of a drum brake wheel cylinder. IMO, the biggest reason that it takes more pedal effort to brake on a vehicle that was designed with power brakes and that has lost power assist is that if the vehicle were designed to take minimal pedal effort without power assist and then you add power assist, the brakes become very touchy and difficult for most drivers to modulate. My dad's '67 Ambassador had very touchy brakes, and in a panic stop, the passengers all got tossed forward against their seat belts. -- Ray O (correct punctuation to reply)
From: C. E. White on 17 Nov 2009 07:51 "Scott in Florida" <MoveOn(a)outa.here> wrote in message news:r7c3g559oa5iv291r66gij86peej7djlrb(a)4ax.com... > On Mon, 16 Nov 2009 09:22:03 -0800 (PST), Mark <makolber(a)yahoo.com> > wrote: > >> >>> >>> It may be possible to make a throttle stick, but here are the laws >>> of >>> physics: >>> No car can overpower its brakes. From any speed. If your foot is >>> on >>> the brake pedal the car will come to a stop. From 10, 20, 80, 120 >>> MPH. >>> I have personally done this on a closed track. When people say the >>> car >>> continues to accelerate despite "pressing with all their might" on >>> the >>> brakes, their foot wasn't on the brake pedal. >>> >>> Simple. End of story.- Hide quoted text - >>> >>> - Show quoted text - >> >>you are wrong, it is not that simple, >> >>at full throttle, there is little vacumm for the brake power >>booster, >>once the storage vacumm is used up you loose the power boost to >>your >>brakes,, >> >>do you think you can over come a full throttle engine with power >>brakes that have lost their power boost... >> >>Mark > > I do.... It seems to me the problem comes in if the driver of a runaway car doesn't brake hard enough soon enough. If you go at it in a timid manner you can overheat the brakes and they will fade out. Once this happens you are in real trouble. I have actually cooked a set of brakes by not doing the right things when coming down a long grade. It is not a pleasant feeling. Still this whole thing is unbelieveable. I can't imagine that they didn't just put the car in neutral. Ed
From: hls on 17 Nov 2009 09:37 "dsi1" <dsi1(a)spamnet.com> wrote in message news:5eqMm.20048 > I doubt there's much validity that vacuum assisted brakes were required > because of the advent of disk brakes. My first car, a 67 Barracuda had > drums and vac boost, as did most cars of the time. That one had a tiny > V8 - a 273! Of course, today that would be a large engine - 4.5L. :-) Power assist brakes, as I said, became luxury items. They were not absolutely necessary on drum brake cars, but certainly made braking effortless. Finally they found their way onto almost every car. Disc brakes on large American cars, without power assist, can be monsters. It is just the way things evolved.
From: Jules on 17 Nov 2009 14:03 On Mon, 16 Nov 2009 13:06:08 -1000, dsi1 wrote: > The Alfa I had was a little weird too. It had a SPICA mechanical fuel > injection that was like a analog/mechanical computer whose workings > scared me to death. The transmission and clutch was in the rear end > which means the driveshaft spun at engine speeds which means the > driveshaft had to be balanced to a high degree but it never was. It also > had nifty inboard disk brakes and a DeDion rear suspension. Urgh, memories of that disk / suspension setup on Rover P6's - it was a real pig to work on because it was so inaccessible :-(
From: dsi1 on 17 Nov 2009 14:44
Jules wrote: > On Mon, 16 Nov 2009 13:06:08 -1000, dsi1 wrote: >> The Alfa I had was a little weird too. It had a SPICA mechanical fuel >> injection that was like a analog/mechanical computer whose workings >> scared me to death. The transmission and clutch was in the rear end >> which means the driveshaft spun at engine speeds which means the >> driveshaft had to be balanced to a high degree but it never was. It also >> had nifty inboard disk brakes and a DeDion rear suspension. > > Urgh, memories of that disk / suspension setup on Rover P6's - it was a > real pig to work on because it was so inaccessible :-( > > My condolences on your Rover. I would have liked to have owned a Jag but after studying the manual, I got scared. :-) |