If you have big performance brakes maybe. But in a normal car the brakes won't stop the engine on full throttle from high speed, they will just overheat and be useless.
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If you have big performance brakes maybe. But in a normal car the brakes won't stop the engine on full throttle from high speed, they will just overheat and be useless.
This story in the OP is about a 458, the very definition of big performance brakes.
In a normal car you'd have even more chance of stopping, the brakes are considerably more powerful than the engine. How easily can a 150bhp car get to 70mph? How quickly can the same car stop from 70? Both the links I posted have examples of normal cars stopping at full throttle.
A hedge and bins apparently.
Don't forget the slowing effect of hitting the kerb and bollards
Ugh you still ignore the fact that this all went pear shaped when the guy had to brake for a roundabout and there is no way the brakes would stop him in the distance he had, this is not just testing on an airfield/long straight road like that article, it is real world. Yes they would EVENTUALLY win assuming they don't overheat first, but the crash is inevitable in a real world scenario unless you pull both paddles and put it in neutral.
I am assuming all those tests were also conducted at speed in a high gear, in this case he had 562bhp pushing in probably second gear which gives the engine a much greater mechanical advantage over those tests you quoted!
Soldato
Had it happen once to me where the peddle got stuck under the mat, luckily it was on a dual carriageway with parking on the side, knocked into neutral and braked with the engine screaming. Did have a slight delay of panic before I stopped mind.
That was in a manual car, is it easy enough to knock into neutral with flappy paddles?
That was in a manual car, is it easy enough to knock into neutral with flappy paddles?
I'm not ignoring that at all, because I don't believe for one second that his car was accelerating by itself when he binned it!
Soldato
Pull both paddles together I believe for some/most, certainly for car in OP.
I'm not ignoring that at all, because I don't believe for one second that his car was accelerating by itself when he binned it!
Fair enough, but the same applies to most scenarios, you won't realise the throttle is stuck until you need to brake
Actually the brakes on "normal" cars are usually much weaker in relation to the engine. So it would be even more difficult to stop, maybe not even possible before the brakes fade. There's still some cheap cars out there which don't even have disks on the rear.
Absolutely! Seriously, I know I've banged on about it, but the podcast I linked to is a very interesting essay on the subject and addresses all the points in the thread. Worth the 40 minutes if you can spare it.Fair enough, but the same applies to most scenarios, you won't realise the throttle is stuck until you need to brake
So the hypothetical "normal car" can speed up faster than it can slow down?
It's nothing to do with speeding up. At high speed if you press the throttle in and the brakes, the brakes on most road cars will overheat, the braking power will fade and they may not be able to stop the car.
With big ceramic or race spec brakes you might be ok. But your not going to have those on 99% of cars and the stopping distance will still be huge.
With big ceramic or race spec brakes you might be ok. But your not going to have those on 99% of cars and the stopping distance will still be huge.
It's everything to do with speeding up. You are saying that the acceleration force applied by the engine is greater than the deceleration force applied by the brakes. For that to be true then the car would be able to accelerate faster at high speed than it can decelerate.
Soldato
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at high speed in high gear the engine's going to have significantly less wheel torque, and this gives the brakes a real advantage. ever try accelerating a car from a standstill in 5th? no because it doesn't have the power.
perfect example: take a burnout, that's the brakes holding the car still while the engine tries to move it forward, and it can't do that even in low gears and high revs with the maximum possible wheel torque.
the stopping distance will be longer sure, but whats just as important is time- it will give you more time than you'd otherwise have to do other things, like kick it into neutral or turn off the engine. now the approaching the roundabout argument only has legs if your standard method of approaching roundabouts is to pull an emergency stop at the last minute leaving no brake overhead, which means the driver is still a tool and would likely crash into something eventually anyway.
Yes it's a lot of energy, but the brakes can easily overcome it.
Let's say your normal car can accelerate to 70mph in 10 seconds, and come to a stop from 70 in 5 seconds. It can decelerate twice as fast as it can accelerate right?
So for simplicity's sake let's say it can speed up at a value of 1 and slow down at -2. What's 1 + -2?
Not to mention that at 70mph the acceleration value is going to be closer to 0.1.
Because I'm certainly not clever enough to calculate the braking forces involved, here's a link to someone else's:
https://sciencing.com/calculate-brake-torque-6076252.html
They say that to stop a 2000kg car from 45mph in 5 seconds would require the brakes to apply 2000Nm of torque to the wheels. How much torque is our normal car applying in top gear at high speed? Probably a tenth of that?
https://sciencing.com/calculate-brake-torque-6076252.html
They say that to stop a 2000kg car from 45mph in 5 seconds would require the brakes to apply 2000Nm of torque to the wheels. How much torque is our normal car applying in top gear at high speed? Probably a tenth of that?
Soldato
I am sure my last car when MOTd had a report on the back that gave the braking effect in kgs, sounded a funny measurment at the time but I think it was to ensure the breaking effect was a certain ratio to vehicle weight.
I believe an engine can be rated into the same system (its basically BHP by a different measure) so should be pretty easy to see the theoretical difference.
There is probably a VOSA guide somewhere
The thing is that brakes only work while they have the capacity to convert kinetic energy into heat, once they reach their capacity of heat generation they simply don't work. The engine alone is gonna generate 419Kw and another 126Kw in Kinetic energy at 50mph assuming around 3 seconds to stop without the engine?
Soldato
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Man of Honour
I agree completely