Motorcycle braking

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Polokid69
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Motorcycle braking

Post by Polokid69 » Tue Jun 21, 2016 9:09 am

Current Bike:
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Previous Bikes:
2007 Kawasaki ZZR600
2012 Kawasaki Ninja 250R
2002 Kawasaki Ninja ZX6
2000 Kawasaki Ninja EX250
1983 Kawasaki GPZ550
1980 Yamaha RD400
1978 Yamaha DT 125
1978 Yamaha YZ 125
1975 Yamaha DT 100

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DarcShadow
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Re: Motorcycle braking

Post by DarcShadow » Tue Jun 21, 2016 10:07 am

While I accept the science as presented they fail to mention weight and momentum. It's a hell of a lot easier to slow down and stop a 500lb motorcycle than it is to slow down and stop a 2000lb car. If they really wanted to prove that a bike can not stop as fast as a car why didn't they show a car's stopping distance from the various speeds.

Gravity = mass * acceleration, in this case deceleration. If both the bike and the car slow at 1G and the car is say 4 times as heavy as the bike it's deceleration is going to be 1/4 of that of the bike.
Acceleration = distance * time, so either the car is going to travel 4 times further than the bike, or take 4 times longer, or some combination there of.

Even at 0.5G brake on the bike, the car is still going to have a deceleration of 1/2 that of the bike.
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JeffStrom
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Re: Motorcycle braking

Post by JeffStrom » Tue Jun 21, 2016 11:41 am

DarcShadow wrote:Gravity = mass * acceleration, in this case deceleration. If both the bike and the car slow at 1G and the car is say 4 times as heavy as the bike it's deceleration is going to be 1/4 of that of the bike.
Acceleration = distance * time, so either the car is going to travel 4 times further than the bike, or take 4 times longer, or some combination there of.

Even at 0.5G brake on the bike, the car is still going to have a deceleration of 1/2 that of the bike.
I think there may be a terminology mismatch, or maybe I completely misunderstand what you are trying to say.
Gravitational force is relative to the mass of the two objects and the distance between them, so gravitational force is not constant. This is convenient because as the mass of the object increases inertia and gravitational force increase together, resulting in a constant acceleration independent of mass. That acceleration being 9.8m/s^2. g-force is not an actual force but is the apparent (felt) reaction to mechanical acceleration relative to the constant 9.8m/s^2. g-force is independent of mass. So, any object accelerating at 1g (9.8m/s^2) will be changing speed at the same rate as any other object. If two objects start at the same speed and decelerate at the same rate, they will stop in the same distance and time. However, the force required to bring the two objects to accelerate/decelerate at the same rate will differ according to the mass of each object.
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Re: Motorcycle braking

Post by DarcShadow » Tue Jun 21, 2016 12:10 pm

Yes, I was mistaking force and gravity. Please ignore my initial post. :)
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Re: Motorcycle braking

Post by JTChiTown » Tue Jun 21, 2016 10:21 pm

Interesting video. I don't like their cuts of motorcycles rear ending vehicles, as all cases were not a question of stopping distance, but rather of safe following distance for proper reaction times.

I think the point they are making is not whether the machine is capable, but whether the average rider exhibits an advantage to stopping relative to an average driver.

In which case, I would agree that this is a resounding NO. Any 15 year old with a leaner permit can stop within 10 feet of a pro in a car (just mash the pedal). How many riders do you know can max out the braking performance of their machines?
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Re: Motorcycle braking

Post by DarcShadow » Tue Jun 21, 2016 11:00 pm

Just like the car, depends on the bike. Bike with ABS, any fool can stop it just as in a car.

This did get me looking though and I did find a video of someone doing a test comparing a car with abs and a bike with abs and they were close enough to each other to be testing error, with the bike stopping just slightly shorter on average.
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