re: What to do in case of a brake failure! I agree with most of what traveller said. Here's my two cents anyways.
1. A lot of cars come with drums at the rear. And since the handbrake is connected to the rear wheels, and drums are really not that effective, i wouldn't rely on them entirely. On a M800, that might work because of it's light weight but i shudder to think of how useless it would be on a toyota fortuner. It's rather useless on my vista as it is. So, i recommend that you familiarize yourself with how your handbrake behaves on an empty road at progressively higher speeds if your car comes with rear brakes.
2. If your comes with rear discs, yes, do exactly what traveller said, pull it slowly. It's entirely possible to lock both rear wheels by pulling too hard on your handbrake too hard. The loss of traction leading to loss of control can be catastrophic. Again, familiarize yourself with how your handbrake behaves.
3. About downshifting- the whole point of downshifting is to use engine braking. Engine braking is higher at higher engine rpms and hence, you downshift.
So, how fast are you supposed to downshift? It all depends on how much you are willing to damage your mechanicals in order to stop the car. Supposing you have a free road in front of you, then i'd recommend switching into the gear whose max speed in gear is just higher than the speed you are at. Supposing you are at 70km/hr in 5th, 2nd tops out at 80 and 3rd at 120, 2nd is the right gear to go two. If you are unsure about these values/ can't think of them in the heat of the moment, two gears down is a good rule of thumb (unless you are redlining your engine, in which case i'm pretty sure you'll be very familiar with where your gears top out).
3. What about the brake?
It all depends on what type of brake failure it is.
If it's brake fade, then stand on the brake like traveller said and apply all the above steps.
If it's catastrophic brake failure, and you are pumping the brake with no effect whatsoever, do it anyway, just in case.
4. So, what of switching off the engine? Don't do it if you are travelling at high speeds. Since most of our cars are front wheel drive, that could cause the *front* wheels to lock. Your steering wheels getting locked is a very very BAD THING. Once you get locked into that kind of slide, with your engine switched off, regaining control in time is improbable. It's either crash or you get lucky and you stop.
Also, a slide itself might just be getting lucky. If you were traveling at a high speed, and your car has a high center of gravity, that's just the perfect recipe for a casino royale style crash (rolling over).
5. Also remember that the common reflex of pressing the clutch in emergency situations is usually a bad thing if your brakes fail.
Signs of brake failure.
1. AFAIK there's no good sign to predict a catastrophic failure. If your brake pedal loses all resistance suddenly, this is the likely cause. Keep your car serviced, make sure you don't use worn out, retreaded tires and keep your head level.
2. Loss of brake assistance. As traveller mentioned, modern cars come with servo assisted brakes. If your brake suddenly becomes wooden, this is the likely cause. Just go stand on your brake pedal as hard as you can and apply any other techniques as necessary.
3. Brake fade. This occurs if you have been riding your brake pedal over a long slope. The brake seems to have normal resistance but the brake doesn't seem to have the usual effect and it gets progressively worse. If you detect this happening, stop riding on your brake, use your engine braking to slow your car down and stop at a safe spot for (not sure here, i've never let this progress too far when i tried to artificially create this, is half hour ok?). Then continue, make sure to use your engine braking afterwards to avoid a repeat.
This all might be a little haphazard, but i just put down everything that came to my head without much organization. Any corrections would be welcome.
Disclaimer-
I'm in no way an expert on this topic. This is all just research and personal opinion |