Threshold braking?
 

Can somebody explain what threshold braking is, and what causes brake fade? Did a search but didn’t find anything.

Sometimes, just searching the forum isn't enough:



http://en.wikipedia.org/wiki/Threshold_braking



http://en.wikipedia.org/wiki/Brake_fade



Threshold braking: braking at the very limit of tire traction, so if you braked ANY harder, your tires would slip and you would start to slide. It's the fastest way to stop a car, if you can ride that edge.



Brake fade: you've used the brakes too hard and too often and the pad & rotor are too hot. Brakes have an optimal use temperature and if they're outside that temperature (too hot in the case of brake fade, but too cold applies as well) they won't work as well as they're supposed to.

Nothing to add besides nice answer. and a +1 to rep. :)

Brake fade is more caused by the brake fluid boiling. This can be because the fluid is old and has absorbed water which really lowers the boiling point. Anyone going out on a track that requires the use of brakes at 100% should have new fluid in the system. It;s a good idea any way to flush the old stuff out every two years regardless. This is assuming you don't have the $20 special pads on the car but good quality pads.

This is becomming a lost art with the advent of ABS. For maximum braking, you step on the pedal as hard as you can really lol, the ABS does the work for you, alternating between the threshold, from lock to unlock way faster and more efficient than you can maximizing traction.

I find threshold braking very simple in my LC accent, because it has the stock 70 series tires. You get lots of warning and feel prior to lockup. My mate's civic has something like 35 series tires and the brake pedal feel is leaden and provides little warning for lockup; you end up 'pulse' braking which is not an effective way to stop.



Keeping everything bled doesn't hurt either.

If you have ABS it's a breeze. Just stab the brakes hard until the rears start to skip from the ABS.

that isn't threshold.. that is ABS. Someone who can master threshold should be able to outstop an ABS system unless its awesome and actually doing threshold braking itself instead of just pulsing.



On that.. because no one really made a point of it. If the car has ABS DO NOT ATTEMPT TO THRESHOLD, like what I quotes said. Put the pedal through the firewall. Any attempts to threshold will result in you hitting whatever you are trying to avoid.. because its dumb.

Do you have any proof of this? I don't know if any human could outstop an ABS.

http://www.drivingfast.net/images/ca...comparison.png

1. Threshold braking



2. ABS braking



3. Locked wheels



4. Cadence braking





I submit this excellent image as proof. :thumbup:



http://www.drivingfast.net/car-contr...#axzz1js1h8nC7 and this highly official looking site... yeah.. lol. I had a better test pdf thing, but I can't find the link and its not worth searching any longer for because 99% of the people driving will screw up threshold braking in an emergency so ABS will normally win.



In that pdf study thing it showed in some situations just locking the freaking tires actually stopped you faster in a very straight line. (I think that was packed snow and gravel, both loose surface situations)



However, the idea that ABS is a magic system that is better than any human and makes you stop faster than the limits of your available traction and ability to convert forward motion into heat (that would be what threshold braking is) is what scares me about adding more safety features. Proof, watch morons in AWD go hauling ass over ice.





edit:

If I remember right the mazda I had would attempt to threshold brake BEFORE it started the ABS pulsing thing. Ill have to do the research into what that car had, but it wasn't just normal ABS if I remember right. Its been a few years. I know it could stop pretty damn fast and I would only feel the "ABS Pulse" in very slick conditions. Normally it was just sort of painful to stop fast with no tires screaming at me. I could be remembering that all wrong... That type of system would be the best because it can do whatever is best at the time.