Speed - "In the last 5m of braking you wipe off half your speed." - Page 3

# Thread: Speed - "In the last 5m of braking you wipe off half your speed."

1. Makes me want to look for a video that compares braking distances between car and motorcycle.

2.

Makes me want to look for a video that compares braking distances between car and motorcycle.
I think, from what I have read in the past, it's almost no contest, ie, the average person, driving a car, equipped with ABS, will be much shorter than a bike.

The motorcycle takes so much more skill to implement a high speed emergency stop, effectively, to use all it can, in the shortest distance....a car, not so much.

I'm sure, if you had a very seasoned racer, doing emergency braking exercises, on a test track, you could get some hugely improved (shorter) distances, but in the real world, where reaction time and skill, and panic come into play, good luck out-braking the average car.

Here is some info to chew on:

http://www.begin-motorcycling.co.uk/elc2.htm

4. Originally Posted by CHIA
I'm sure, if you had a very seasoned racer, doing emergency braking exercises, on a test track, you could get some hugely improved (shorter) distances, but in the real world, where reaction time and skill, and panic come into play, good luck out-braking the average car.
If someone can find a good video or other supporting data on this, it would deserve to be another sticky. I was very surprised to hear that, as I always assumed a bike would stop much faster due to the low weight. I believe it now, but I bet a lot of people still think they can stop quicker on their bikes.

5.

6. Thanks for posting this video. I have a loving wife and two little girls that expect me to come home every day. A message like this helps keep things in perspective. We all need to be careful out there.

7. ## For The Disbelievers

KE=mv^2/2

That is the equation for kinetic energy, and as you can see, KE is proportional to the square of velocity. KE is what your brakes are turning into heat when you make each and every stop.

SO, plugging in some numbers for a 1000 Kg object:

v= 100, KE = 5000000
v= 90, KE = 4050000, 81% of original KE
v= 80, KE = 3200000, 64% of original KE
v= 70, KE = 2450000, 49% of original KE -just 30 M/s slower, but only half KE!
v= 60, KE = 1800000, 36% of original KE
v= 50, KE = 1250000, 25% of original KE -half the speed, a quarter of top KE!
v= 40, KE = 800000
v= 30, KE = 450000
v= 20, KE = 200000
v= 10, KE = 50000
v= 5, KE = 12500
v= 2.5, KE = 3125
v= 1, KE = 500
v= 0, KE = 0

If this is not making sense to you, read it from the bottom up and see how much KE you accumulate with each 10 units of speed.

You can see your brakes have a much bigger job to do with each 10 units of speed.

8. Originally Posted by made Man
situational awareness does a lot more than going 5kph slower.
thank you.

every time i see these dramatic "speed kills" videos/ads, i wanna puke. where do they suggest to PAY ATTENTION while you drive down the road at 60 mph???

as mentioned above, the kinetic energy of an object is directly proportional to the square of its speed. the amount of kinetic energy in your vehicle between the speeds of 60 and 65 is MUCH greater that between 0 and 5. basic physics.

speed doesn't kill, stupid does.

9. Originally Posted by avocet
thank you.

every time i see these dramatic "speed kills" videos/ads, i wanna puke. where do they suggest to PAY ATTENTION while you drive down the road at 60 mph??? as mentioned above, the kinetic energy of an object is directly proportional to the square of its speed. the amount of kinetic energy in your vehicle between the speeds of 60 and 65 is MUCH greater that between 0 and 5. basic physics.

speed doesn't kill, stupid does.

Somewhat contradictory statements there. You state that "speed kills" statements make you puke, then go on to say that you understand the physics. I'm sure you understand the numbers, but how it relates to real life... I dunno. Obviously paying attention is critical, and we all think we ride safe (and most don't IMO), but when something truly unexpected happens - ie. merely paying attention is no longer going to save your ass - having physics on your side rather than against you is kind of important.

My

10. Very interesting.

11. Here's some actual and average data for
1. Motorcycle stopping distance
http://www.msf-usa.org/imsc/proceedi...ngdistance.pdf

2. Vehicle stopping distance
http://www.passmytheory.co.uk/learni...gdistance.aspx

For motorcycles, the finding was that ABS helped in terms of consistency between stops, but the shorter braking distance was consistently w/o ABS, at the lower speed (30mph), at 80 mph the ABS equipped model consistently had a shorter stopping distance. In most cases it was only <5% difference either way, except for the heavy bikes.

Still, best braking distance of the 4 bikes tested came from the FJR 1300,
30 mph - 10.40m
80 mph - 67.46m

Comparison to the *average* distances in the second link
30 mph - 14m
70 mph - 75m

According to car and driver's 2008 stopping distance test, a 911s they tested had a stopping distance of 93m from 70mph, it was the best of the bunch.

So based on that I would say from real-world testing data, your average motorcycle will be able to out-stop your average car. If the rider screws up and bins it, well....

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