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Bicycle Stopping Distances



 
 
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  #11  
Old November 2nd 09, 04:15 AM posted to rec.bicycles.racing
DirtRoadie
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Posts: 2,915
Default Bicycle Stopping Distances

On Nov 1, 5:50*pm, Anton Berlin wrote:

However as we all know it's more prudent to run over cyclists from
behind if you want to avoid the legal tangles.

In fact it might be one of the easiest ways on the planet to kill
someone without consequences.


I respectfully disagree. My impression, based upon an experience I
had, is that it would be easy for the driver of a motorized vehicle to
do insure damage by pulling closely in front of a paceline or similar
group of cyclists, hitting the brakes and causing the front riders to
also hit their brakes. This causes the following riders to plow into
the leading riders and if done properly, causes them all to crash in a
nice pileup. If executed by a skilled perpetrator there need not be
any contact between the car and riders and the driver can depart with
no physical evidence of any involvement. After all, a broken rear
window and/or blood is far too messy.

In the LA road rage trial, relative braking distances and/or
capabilities of bikes vs. cars is a red herring thrown in by sleazy
defense counsel trying to divert the jury's attention from the fact
that the dear doctor performed a deliberate and illegal act which
caused exactly the illegal results which might have been expected.

DR



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  #12  
Old November 2nd 09, 04:19 AM posted to rec.bicycles.racing
DirtRoadie
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Posts: 2,915
Default Bicycle Stopping Distances

On Nov 1, 5:50*pm, "Tom Kunich" wrote:

The reaction time for both the driver and the rider are the same and so can
be ignored when discussing stopping distances at equal speeds.


Huh? How can the driver's "reaction time" be relevant what he has
nothing to react to?


  #13  
Old November 2nd 09, 04:25 AM posted to rec.bicycles.racing
RicodJour
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Posts: 3,142
Default Bicycle Stopping Distances

On Nov 1, 10:19*pm, DirtRoadie wrote:
On Nov 1, 5:50*pm, "Tom Kunich" wrote:

The reaction time for both the driver and the rider are the same and so can
be ignored when discussing stopping distances at equal speeds.


Huh? How can the driver's "reaction time" be relevant what he has
nothing to react to?


TK is talking absolute/objective, your are talking relative/
subjective.
You are both right, but, as usual, I am more right.

R
  #14  
Old November 2nd 09, 04:44 AM posted to rec.bicycles.racing
Tom Kunich
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Posts: 892
Default Bicycle Stopping Distances

"DirtRoadie" wrote in message
...
On Nov 1, 5:50 pm, "Tom Kunich" wrote:

The reaction time for both the driver and the rider are the same and so
can
be ignored when discussing stopping distances at equal speeds.


Huh? How can the driver's "reaction time" be relevant what he has
nothing to react to?


I'm speaking purely of stopping ability as on a test course.

In the case of the relevant assault, since it takes between .7 and 1.5
seconds or so to react, and if the driver cut in close enough there wouldn't
be sufficient time to react and hence no way whatsoever to avoid running
into the back of the car.


  #15  
Old November 2nd 09, 12:39 PM posted to rec.bicycles.racing
Joe
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Posts: 37
Default Bicycle Stopping Distances


"Tom Kunich" wrote in message
m...
"Ryan Cousineau" wrote in message
]...
In article
,
Anton Berlin wrote:

In a head to head test and in normal conditions a bike should be able
to stop faster than a car.

But that includes that the rider has both hands on the bars (and
brakes) which is hard to do when you're flipping someone off.

At 50 kmh

http://www.exploratorium.edu/cycling/brakes2.html

Bike stops in 10 meters

http://www.forensicdynamics.com/stopdistcalc

Car stops in 14 meters.

I hate proving Kunich wrong (again) at the expense of proving Magilla
right.

But Kunich may be right on an empirical basis. It make take several
hundred meters to slow his fat ass to a stop.

Besides this is all theory as we know Kunich has never gone 30 mph on
a bike.


The missing factor is essentially reaction time, which probably explains
how Dr. Evil managed to whomp two riders with his trunk.

Here's a claim that reaction times vary around 0.7-1.5 s for drivers in
braking situations.

That suggests that if the Doctor swerved and braked fast enough, the
riders would not have had time to react before hitting the car. He's
effectively got about a 1-second head start on braking, and at 50 km/h,
that's about 14 meters.

In other words, the car could be at zero km/h before the riders got to
their brakes, and the rest depends on how closely in front of them he
cut.

Considering he seems to have been trying to injure them, I'm going to
guess really close, like 5m.

I figure that scenario as being 14 metres of stopping distance but about
24 metres of rt+ideal stopping. In other words, physics says those
cyclists were gonna hit the car no matter how good their brakes, as long
as their reaction times were within human norms.

Gerbils or monkeys may have better reaction times than humans, though.


As usual, those who fail to think do the most talking.

The brakes on a modern car will stop the car at a rate of about one gee.
Race cars commonly brake well above one gee. Moreover, car tires, which
cover a large portion of the road and put more square inches of rubber on
the road per lb. of load, are less susceptible to road conditions, gravel
etc. on the road and other traction problems.

Because of the high center of gravity a bicycle has, the braking force you
can apply while sitting normally on the saddle is about 1/2 gee. Got that?
HALF the braking force of a car. You can increase your braking force to
perhaps .85 gees by sliding backwards and putting your stomach on the
saddle. This unfortunately greatly decreases your control of the bicycle
while increasing your ability to brake by lowering your center of gravity.
Note that normally the time to slide back like that would take more
time/distance than the slightly improved braking would justify.

The reaction time for both the driver and the rider are the same and so
can be ignored when discussing stopping distances at equal speeds.


gee whiz


  #16  
Old November 2nd 09, 03:53 PM posted to rec.bicycles.racing
Anton Berlin
external usenet poster
 
Posts: 3,381
Default Bicycle Stopping Distances

On Nov 2, 5:39*am, "Joe" wrote:
"Tom Kunich" wrote in message

m...



"Ryan Cousineau" wrote in message
]...
In article
,
Anton Berlin wrote:


In a head to head test and in normal conditions a bike should be able
to stop faster than a car.


But that includes that the rider has both hands on the bars (and
brakes) which is hard to do when you're flipping someone off.


At 50 kmh


http://www.exploratorium.edu/cycling/brakes2.html


Bike stops in 10 meters


http://www.forensicdynamics.com/stopdistcalc


Car stops in 14 meters.


I hate proving Kunich wrong (again) at the expense of proving Magilla
right.


But Kunich may be right on an empirical basis. *It make take several
hundred meters to slow his fat ass to a stop.


Besides this is all theory as we know Kunich has never gone 30 mph on
a bike.


The missing factor is essentially reaction time, which probably explains
how Dr. Evil managed to whomp two riders with his trunk.


Here's a claim that reaction times vary around 0.7-1.5 s for drivers in
braking situations.


That suggests that if the Doctor swerved and braked fast enough, the
riders would not have had time to react before hitting the car. He's
effectively got about a 1-second head start on braking, and at 50 km/h,
that's about 14 meters.


In other words, the car could be at zero km/h before the riders got to
their brakes, and the rest depends on how closely in front of them he
cut.


Considering he seems to have been trying to injure them, I'm going to
guess really close, like 5m.


I figure that scenario as being 14 metres of stopping distance but about
24 metres of rt+ideal stopping. In other words, physics says those
cyclists were gonna hit the car no matter how good their brakes, as long
as their reaction times were within human norms.


Gerbils or monkeys may have better reaction times than humans, though.


As usual, those who fail to think do the most talking.


The brakes on a modern car will stop the car at a rate of about one gee..
Race cars commonly brake well above one gee. Moreover, car tires, which
cover a large portion of the road and put more square inches of rubber on
the road per lb. of load, are less susceptible to road conditions, gravel
etc. on the road and other traction problems.


Because of the high center of gravity a bicycle has, the braking force you
can apply while sitting normally on the saddle is about 1/2 gee. Got that?
HALF the braking force of a car. You can increase your braking force to
perhaps .85 gees by sliding backwards and putting your stomach on the
saddle. This unfortunately greatly decreases your control of the bicycle
while increasing your ability to brake by lowering your center of gravity.
Note that normally the time to slide back like that would take more
time/distance than the slightly improved braking would justify.


The reaction time for both the driver and the rider are the same and so
can be ignored when discussing stopping distances at equal speeds.


gee whiz- Hide quoted text -

- Show quoted text -


A gee-nius?
  #17  
Old November 2nd 09, 06:27 PM posted to rec.bicycles.racing
z
external usenet poster
 
Posts: 761
Default Bicycle Stopping Distances

Anton Berlin wrote:
On Nov 2, 5:39 am, "Joe" wrote:
"Tom Kunich" wrote in message

m...



"Ryan Cousineau" wrote in message
]...
In article
,
Anton Berlin wrote:
In a head to head test and in normal conditions a bike should be able
to stop faster than a car.
But that includes that the rider has both hands on the bars (and
brakes) which is hard to do when you're flipping someone off.
At 50 kmh
http://www.exploratorium.edu/cycling/brakes2.html
Bike stops in 10 meters
http://www.forensicdynamics.com/stopdistcalc
Car stops in 14 meters.
I hate proving Kunich wrong (again) at the expense of proving Magilla
right.
But Kunich may be right on an empirical basis. It make take several
hundred meters to slow his fat ass to a stop.
Besides this is all theory as we know Kunich has never gone 30 mph on
a bike.
The missing factor is essentially reaction time, which probably explains
how Dr. Evil managed to whomp two riders with his trunk.
Here's a claim that reaction times vary around 0.7-1.5 s for drivers in
braking situations.
That suggests that if the Doctor swerved and braked fast enough, the
riders would not have had time to react before hitting the car. He's
effectively got about a 1-second head start on braking, and at 50 km/h,
that's about 14 meters.
In other words, the car could be at zero km/h before the riders got to
their brakes, and the rest depends on how closely in front of them he
cut.
Considering he seems to have been trying to injure them, I'm going to
guess really close, like 5m.
I figure that scenario as being 14 metres of stopping distance but about
24 metres of rt+ideal stopping. In other words, physics says those
cyclists were gonna hit the car no matter how good their brakes, as long
as their reaction times were within human norms.
Gerbils or monkeys may have better reaction times than humans, though.
As usual, those who fail to think do the most talking.
The brakes on a modern car will stop the car at a rate of about one gee.
Race cars commonly brake well above one gee. Moreover, car tires, which
cover a large portion of the road and put more square inches of rubber on
the road per lb. of load, are less susceptible to road conditions, gravel
etc. on the road and other traction problems.
Because of the high center of gravity a bicycle has, the braking force you
can apply while sitting normally on the saddle is about 1/2 gee. Got that?
HALF the braking force of a car. You can increase your braking force to
perhaps .85 gees by sliding backwards and putting your stomach on the
saddle. This unfortunately greatly decreases your control of the bicycle
while increasing your ability to brake by lowering your center of gravity.
Note that normally the time to slide back like that would take more
time/distance than the slightly improved braking would justify.
The reaction time for both the driver and the rider are the same and so
can be ignored when discussing stopping distances at equal speeds.

gee whiz- Hide quoted text -

- Show quoted text -


A gee-nius?


The proper rbr term is gee-nus
  #18  
Old November 2nd 09, 06:44 PM posted to rec.bicycles.racing
Paul B. Anders
external usenet poster
 
Posts: 363
Default Bicycle Stopping Distances

On Nov 1, 10:09*am, Anton Berlin wrote:
In a head to head test and in normal conditions a bike should be able
to stop faster than a car.

But that includes that the rider has both hands on the bars (and
brakes) which is hard to do when you're flipping someone off.

At 50 kmh

http://www.exploratorium.edu/cycling/brakes2.html

Bike stops in 10 meters

http://www.forensicdynamics.com/stopdistcalc

Car stops in 14 meters.

I hate proving Kunich wrong (again) at the expense of proving Magilla
right.

But Kunich may be right on an empirical basis. *It make take several
hundred meters to slow his fat ass to a stop.

Besides this is all theory as we know Kunich has never gone 30 mph on
a bike.


Plug in 50 mph. Anyone who has done any high-speed descending who
believes a bike can stop from 50 mph in under 100 feet is smoking
weed. It's laughable. Go descend Carson or Monitor passes in the
Sierra's, where you can hit 50 mph easily, and do a full-on panic stop
and see if you can do this.

Brad
  #19  
Old November 2nd 09, 08:04 PM posted to rec.bicycles.racing
Diablo Scott[_2_]
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Posts: 22
Default Bicycle Stopping Distances

On Nov 2, 9:44*am, "Paul B. Anders" wrote:

Plug in 50 mph. Anyone who has done any high-speed descending who
believes a bike can stop from 50 mph in under 100 feet is smoking
weed. It's laughable. Go descend Carson or Monitor passes in the
Sierra's, where you can hit 50 mph easily, and do a full-on panic stop
and see if you can do this.

Brad


The calculator assumes a flat road; stopping distance on a 10%
downhill is obviously quite a bit longer.
They had to assume some total mass also, but weren't specific there.
  #20  
Old November 2nd 09, 09:47 PM posted to rec.bicycles.racing
Joe
external usenet poster
 
Posts: 37
Default Bicycle Stopping Distances


"Diablo Scott" wrote in message
...
On Nov 2, 9:44 am, "Paul B. Anders" wrote:

Plug in 50 mph. Anyone who has done any high-speed descending who
believes a bike can stop from 50 mph in under 100 feet is smoking
weed. It's laughable. Go descend Carson or Monitor passes in the
Sierra's, where you can hit 50 mph easily, and do a full-on panic stop
and see if you can do this.

Brad


The calculator assumes a flat road; stopping distance on a 10%
downhill is obviously quite a bit longer.
They had to assume some total mass also, but weren't specific there.

If I'm *ever* able to hit 50mph on a flat road, the absolute *last* thing on
my mind will be stopping.

LOL


 




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