Braking Distances - Which car determined the 'standard'?
Discussion
Kozy said:
As above, the only thing that increased energy does in increase the heat generated. The force can remain constant regardless.
Yeah, I shouldn't be allowed to think about physics in the morning.What I meant to express was that the amount of energy that the brakes effectively absorb at a given pedal input might be roughly linear over time (rather than the braking force), but I don't think that's the case either.
p1esk said:
My feeling has always been that when driving in wet weather, the discs will constantly throw all the water off, apart from a very thin film, and as soon as the brakes are applied that bit of moisture will dry off immediately
If I pressure wash my car and go for a drive, the brakes don't work for a good few seconds at 20mph or so, enough to be a risk. I can't say I've ever experienced the same after going through standing water or whatever, because presumably less accumulates, but the 'try your brakes' signs after fords certainly make sense.trashbat said:
p1esk said:
My feeling has always been that when driving in wet weather, the discs will constantly throw all the water off, apart from a very thin film, and as soon as the brakes are applied that bit of moisture will dry off immediately
If I pressure wash my car and go for a drive, the brakes don't work for a good few seconds at 20mph or so, enough to be a risk. I can't say I've ever experienced the same after going through standing water or whatever, because presumably less accumulates, but the 'try your brakes' signs after fords certainly make sense.p1esk said:
OK, so it can be a problem with very low speed driving, but at all normal speeds I would expect even large quantities of water to be thrown off very quickly. I may or may not be right about that.
I remember merrily going down a 30mph road for some distance, and upon needing to brake, discovering that it took a couple of car lengths extra to stop. It only seems to happen after pressure washing, so is perhaps related to how well water penetrates certain areas, but I don't think it's shed as easily as you think. Whether the same thing can happen in ordinary road driving is less obvious.
trashbat said:
...but the 'try your brakes' signs after fords certainly make sense.
Definitely a good idea to pump your brakes a few times after a ford, or you might not be able to stop before the next one! Been there done that, not a good feeling coming over a blind crest after a ford to see another one and finding the brake pedal makes no difference...
GravelBen said:
trashbat said:
...but the 'try your brakes' signs after fords certainly make sense.
Definitely a good idea to pump your brakes a few times after a ford, or you might not be able to stop before the next one! Been there done that, not a good feeling coming over a blind crest after a ford to see another one and finding the brake pedal makes no difference...
Vipers said:
GravelBen said:
trashbat said:
...but the 'try your brakes' signs after fords certainly make sense.
Definitely a good idea to pump your brakes a few times after a ford, or you might not be able to stop before the next one! Been there done that, not a good feeling coming over a blind crest after a ford to see another one and finding the brake pedal makes no difference...
Hello "Vipers"
In reply to your earlier post about "have I tried stopping from 30 mph with learners?".....yes frequently.
I have now switched to a BMW MINI and the brakes are much better than the Corsa I used to teach in. The BMW/MINI has disc's all round, where as the corsa had drums on the back. The Mini brakes are brilliant, but for the learner to "learn" what "gebtly braking" means does take some getting used to (hence learner cars often have words simular to "Keep your distance" on the back of them)
The mini can stop from 30 in a little over a car length in the dry....that spanks the HWC figures, but getting back to the original question.....there are still cars on the road that may well need about 6 car lengths to stop from 30. The HWC is also a "guide" to way we should use the roads, and on stopping distances it clearly states the word "Typical" not "These are the.."
every car is different, every road surface is different, the weather, your health/alertness, your brakes, your tyres, your pressure in each car tyre maybe different, your ability at times may not be what you think it is, all these factors contribute to how well your car does/does not stop in an emergency situation. Some of the comments above are not really helping. Drive to the conditions, the within cars ability, your ability and being able to stop safely in the distance you can see to be clear in front of you....allowing for the turnip driving behind you too closely should hopefully mean none of us ever have to do an emergency stop.......if your ABS kicks in, or you skid (non ABS car......then the first thing we should do is question ourselves as to why we braked too hard? why didn't we brake earlier and more gently? We should never have to use our ABS....simples
In reply to your earlier post about "have I tried stopping from 30 mph with learners?".....yes frequently.
I have now switched to a BMW MINI and the brakes are much better than the Corsa I used to teach in. The BMW/MINI has disc's all round, where as the corsa had drums on the back. The Mini brakes are brilliant, but for the learner to "learn" what "gebtly braking" means does take some getting used to (hence learner cars often have words simular to "Keep your distance" on the back of them)
The mini can stop from 30 in a little over a car length in the dry....that spanks the HWC figures, but getting back to the original question.....there are still cars on the road that may well need about 6 car lengths to stop from 30. The HWC is also a "guide" to way we should use the roads, and on stopping distances it clearly states the word "Typical" not "These are the.."
every car is different, every road surface is different, the weather, your health/alertness, your brakes, your tyres, your pressure in each car tyre maybe different, your ability at times may not be what you think it is, all these factors contribute to how well your car does/does not stop in an emergency situation. Some of the comments above are not really helping. Drive to the conditions, the within cars ability, your ability and being able to stop safely in the distance you can see to be clear in front of you....allowing for the turnip driving behind you too closely should hopefully mean none of us ever have to do an emergency stop.......if your ABS kicks in, or you skid (non ABS car......then the first thing we should do is question ourselves as to why we braked too hard? why didn't we brake earlier and more gently? We should never have to use our ABS....simples
watchnut said:
the HWC figures
HWC figues aren't relevant in the real world, because reaction time counts for more when something truly unexpected happens. It's been shown to take your brain anything up to 2 seconds to start braking when something wholly unexpected happens. For example, see what's written about inattentional blindness and road safety. The HWC braking distances use an extremely optimistic 0.67 second reaction time. A 17 year-old with twenty years driving experience might manage that
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