We Test 'Braking Distance' In A BMW M3 [Video]

The time it takes your car to come to a complete stop after slamming on the brakes can be the difference between life and death. But how much "braking distance" does all that extra speed actually add? In a bid to find out, we tested BMW's anti-lock braking system (ABS) on an M3 sports car while travelling at 80km/h and 100km/h. Check out the video to see how many car lengths were added -- the result may surprise you.

This week, we attended the BMW Driving Experience at Eastern Creek Raceway. The event provides hands-on driving techniques and safety skills in a range of BMW sports cars with an emphasis on high-speed maneuvering. (Stay tuned for an in-depth feature coming soon.)

One of the more straightforward tests involved slamming down the brakes in an M3 while driving at high speed on a wet tarmac. The braking test was conducted twice -- once at 80 kilometres an hour and again at 100 kilometres an hour. Here's how the car handled in both tests:

As you can see, adding 20km to your overall speed can make a hell a lot of difference if you need to brake suddenly -- and this was in a $100,000+ BMW with brand new tyres and a state-of-the-art ABS system. You can imagine that the average car would fare considerably worse.

Our BMW Driving Experience instructor said that all drivers should be required to experience this braking demonstration as part of their provisional training. We're inclined to agree.


    Who would have thought that if you are going faster it will take longer to stop... that sounds crazy

      The point of the video is to show how much longer,

        There was an advert on Australian TVs going back to the introduction of the 50km/h standard that spoke on the same sort of issue. Taking the same facts from that, the NSW RTA issued a fact sheet with the same info contained, namely this quote;

        "Two cars of equal weight and braking ability are travelling along the same road. Car 1, travelling at 60 km/h, is overtaking Car 2, which is travelling at 50 km/h. A child on a bicycle – let's call him Sam – emerges from a driveway 29 metres away just as the two cars are side-by-side. The drivers both see Sam at the same time and both take 1.2 seconds before they fully apply their brakes.

        In the few moments it takes to react and stop, Car 2 would have had enough space in which to stop without hitting Sam. Car 1, on the other hand, would be travelling at 44 km/h when it hits Sam and at this speed, it is highly likely that Car 1 would have seriously injured or even killed Sam."

        Enough said.

        Edit for source: http://www.rms.nsw.gov.au/saferroadsnsw/speeding_and_crashes.pdf

        Last edited 13/05/14 7:42 pm

      The point is that 25% more speed didn't add 25% longer braking distance, it added 56% more. People always seem to think a little bit more speed just requires a little bit more braking when in fact braking distance is exponentially proportional to speed.

      The principal is clearly demonstrated with the Veyron. At 400kmph it takes just over 500 metres for that car to come to a standstill even with its amazing aero-braking, much wider tires, bigger brakes etc. 4 times the speed and yet it still takes a car that costs US$6.25 million 5 times as long to come to a stop.

    To save you time watching the vid; the braking distance is seven car lengths longer at 100km/h compared to 80km/hr. Or about 31m further.

      Or to back it up with some science. Your Kinetic energy is your (mass multiplied by your speed) squared.

      So every time you double your speed, you have four times the kinetic energy. This means you take four times longer to stop, plus the distance you travel during your reaction time.

      At 100km/h you have 1.56 times the kinetic energy as you do at 80km/h. Therefore, you will take about 1.56 times the distance to stop.

      It's called physics. It's fun to learn.

      The comment " and this was in a $100,000+ BMW with brand new tyres and a state-of-the-art ABS system. " is utter crap, unless new tyres and ABS is more effective at high speed than at low speed, since the increase in stopping distance is purely a function of the amount of energy you need to wipe off.

      Sure, the BMW is 'only' 31m further than it's original stopping distance of about 60 meters.

      I bet A 1956 Ford Victoria Lead Sled would take in roughly 1.56 times the distance to stop at 100km/h as it would to stop at 80km/h. Just as this BMW has.

        So you're saying brake effectiveness and tyre tread have zero influence on stopping distance? Really?

          @chrisjager: I'm saying that brake effectiveness and tire tread have the same influence on the stopping distance at 80km/h as it does at 100km/h.

          In absolute terms, a car with terrible breaks and tires is going to take longer to stop than one with fantastic breaks and tires; but both cars will take more than one and a half times the distance to stop at 100 kmh than they do at 80kmh.

          The critical factor at play is the amount of kinetic energy that the brakes and tires need to dissipate, and that is influenced by the speed and mass of the vehicle, not is stopping capability.

          The assumption I am making is that the breaks on the car have a generally liner ability to wipe off energy. This assumption would be invalid if you overheat your beaks, but you're unlikely to do that stoppping from 100km/h, even in an old car.

    I am so glad LifeHacker tested this for me, otherwise I might never have cared.

    Perhaps what should really be tested as part of provisional training is the ability to pay attention while driving and to drive defensively (which isn't the same as driving slower).

    I don't understand why there isn't a day of actual driver training required to get a car licence, like a motorbike licence?

    Doesn't change the story, but you weren't driving an M3 in the video! :)

    The car is not an M3, its the new 4 series coupe.

    the thing i would like, is to get an EL falcon on old tires and a brand new VE commodore and do the test.

    just to show the public that the commercials that the TAC uses are soo out of date its not funny.

    what about, showing what happens when the child has a proper parent and it doesn't cross onto the road?

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