From: DanKMTB on
On Jul 9, 12:23 pm, Brent P <tetraethylleadREMOVET...(a)yahoo.com>
wrote:
> On 2008-07-09, Jim Yanik <jya...(a)abuse.gov> wrote:
>
> > unless you're on a sandy,dirty,oily,or icy road,bikes can stop in very
> > short distances. Without tossing yourself over the handlebars....
>
> Um... bicycles take longer to stop than most cars from the same
> speed.

Do you really think so? I can stop my bikes pretty darn quick. In
approximately one bike length if I don't mind tumbling over the
handlebars, but even without the tumble I can stop very shortly. All
the weight back, but over the rear tire, and grab the front brakes.
Pull until rear wheel is airborne and approaching flipover point,
modulate as necessary. How long do you figure it takes the average
car to stop from 25mph? I'd bet I could stop shorter on a bicycle.
Very high performance cars may give me a run for my money.

> Basic physics of contact patch and swept braking area are in
> play. A road bicycle has very little of each.

You forgot mass you're bringing to a stop. Since the bicycle also has
very little mass in motion, it needs much less of a contact patch.
From: Matthew T. Russotto on
In article <c157c134-8158-44f7-9fd5-dc462835bff2(a)t54g2000hsg.googlegroups.com>,
DanKMTB(a)gmail.com <DanKMTB(a)gmail.com> wrote:
>On Jul 9, 12:23 pm, Brent P <tetraethylleadREMOVET...(a)yahoo.com>
>wrote:
>> On 2008-07-09, Jim Yanik <jya...(a)abuse.gov> wrote:
>>
>> > unless you're on a sandy,dirty,oily,or icy road,bikes can stop in very
>> > short distances. Without tossing yourself over the handlebars....
>>
>> Um... bicycles take longer to stop than most cars from the same
>> speed.
>
>Do you really think so? I can stop my bikes pretty darn quick. In
>approximately one bike length if I don't mind tumbling over the
>handlebars, but even without the tumble I can stop very shortly. All
>the weight back, but over the rear tire, and grab the front brakes.
>Pull until rear wheel is airborne and approaching flipover point,
>modulate as necessary. How long do you figure it takes the average
>car to stop from 25mph? I'd bet I could stop shorter on a bicycle.
>Very high performance cars may give me a run for my money.

A car with 1g coefficient of friction between its tires and asphalt
can stop from 25mph in about 21 feet. A bicycle with 1g coefficient
of friction between its tires and asphalt cannot, because the rider
will be thrown from the bike before he stops. That is why a bicycle
takes longer than a car to stop.

>> Basic physics of contact patch and swept braking area are in
>> play. A road bicycle has very little of each.
>
>You forgot mass you're bringing to a stop. Since the bicycle also has
>very little mass in motion, it needs much less of a contact patch.

At low speed, to first order, mass is not a factor. Nor is the
contact patch or the swept braking area; they come into play for
a higher-speed stop however, or for braking multiple times in succession.
--
There's no such thing as a free lunch, but certain accounting practices can
result in a fully-depreciated one.
From: Brent P on
On 2008-07-09, DanKMTB(a)gmail.com <DanKMTB(a)gmail.com> wrote:

> Do you really think so? I can stop my bikes pretty darn quick. In
> approximately one bike length if I don't mind tumbling over the
> handlebars, but even without the tumble I can stop very shortly. All
> the weight back, but over the rear tire, and grab the front brakes.
> Pull until rear wheel is airborne and approaching flipover point,
> modulate as necessary. How long do you figure it takes the average
> car to stop from 25mph? I'd bet I could stop shorter on a bicycle.
> Very high performance cars may give me a run for my money.

Sorry, not from 30+mph on a downhill you aren't. Or 30mph period. I am
not talking normal car braking vs. full out bicycle braking. I am
talking full decel possible of both from the same speed.

Remember, I ride and drive. I know full well the limitations of the
bicycle brakes.

>> Basic physics of contact patch and swept braking area are in
>> play. A road bicycle has very little of each.

> You forgot mass you're bringing to a stop. Since the bicycle also has
> very little mass in motion, it needs much less of a contact patch.

I didn't forget it. I live it.




From: DanKMTB on
On Jul 9, 5:49 pm, Brent P <tetraethylleadREMOVET...(a)yahoo.com> wrote:
> On 2008-07-09, DanK...(a)gmail.com <DanK...(a)gmail.com> wrote:
>
> > Do you really think so?  I can stop my bikes pretty darn quick.  In
> > approximately one bike length if I don't mind tumbling over the
> > handlebars, but even without the tumble I can stop very shortly.  All
> > the weight back, but over the rear tire, and grab the front brakes.
> > Pull until rear wheel is airborne and approaching flipover point,
> > modulate as necessary.  How long do you figure it takes the average
> > car to stop from 25mph?  I'd bet I could stop shorter on a bicycle.
> > Very high performance cars may give me a run for my money.
>
> Sorry, not from 30+mph on a downhill you aren't. Or 30mph period. I am
> not talking normal car braking vs. full out bicycle braking. I am
> talking full decel possible of both from the same speed.  

I agree. I'm sure the edmunds distances are max stopping in deal
conditions. I am thining of the same on my bike.


> Remember, I ride and drive.

I know. That's one of the reasons I responded to you.


> I know full well the limitations of the
> bicycle brakes.

If you wouldn't mind, describe your max braking technique for your
bike. How much of the lever(s) you pull in, which levers, body
position, does the rear wheel unweight or lift?


> >> Basic physics of contact patch and swept braking area are in
> >> play. A road bicycle has very little of each.
> > You forgot mass you're bringing to a stop.  Since the bicycle also has
> > very little mass in motion, it needs much less of a contact patch.
>
> I didn't forget it.  I live it.

From: Brent P on
On 2008-07-10, Jim Yanik <jyanik(a)abuse.gov> wrote:

> in wet/slick conditions,one gives themselves more braking distance.
> if your bike has such lousy braking characteristics,then you have no
> business GOING 30mph,or even being on a public road.
> It certainly is not 'cricket' to blame others for that shortcoming of your
> choice of vehicle. it's called "going too fast for conditions";the
> conditions being your equipment.

With a bicycle you can change directions easily. This is what you use in
emergencies. You don't panic brake like some idiot driving a car. You
do that you're gonna meet the pavement.

> I doubt Brent was actually going "30MPH" when that woman moved in front of
> him and braked.

I was going about 17mph. Perfectly acceptable when you have two and
half car lengths of space remaining in front of you. I certainly
wouldn't have been driving faster in the same location and nobody has
ever pulled that move on me when I've been driving. Only when biking.