warren said:In article said:warren wrote:
Quoted message said:Quoted message said:Quoted message said:You'd have more control and reduce speed quicker with some braking applied to the rear wheel
than none.
That defies the laws of physics.
Read what I said. "You'd have more control..."
Not necessarily. In many situations, using the just the front brake gives both better control
(decreases the chance of rear wheel skid) _and_ potential for faster deceleration.
Quoted message said:Quoted message said:At least when riding in a straight line, using both brakes can not produce maximum stopping force.
Ridiculous!
No, it is a fact. At the limit of braking, so much weight has been shifted to the front wheel, that
there is not enough traction at the rear tire to provide any significant stopping. What is
ridiculous is your apparent refutation of the realities of physics.
Quoted message said:Quoted message said:Quoted message said:#1) Tell us then, in a straight line like Beloki was in, how do you get
your rear wheel to go out to the side if the rear wheel is braked too much and the front is not
braked enough? That would be a straight skid.
Because as the brakes are applied, the weight balance is moved forward (regardless of which brake
is used). This means the front wheel gains traction while the rear wheel losses traction. With
reduced traction available at the rear, excessive rear braking can result in a skid, whereas with
more front wheel braking, it may not.
You didn't answer the question. "How do you get the rear wheel to go to the side...?" And you are
forgetting the all important ability to steer predictably.
Yes, I did answer the question. Beloki wasn't going in a completely straight line, he was turning
slightly. At a given braking deceleration, weight will be shifted forward to a certain degree,
decreasing rear traction. This rear traction can be used for some combination of lateral force
(turning) or longitudinal force (braking). If you use up too much of the remaining traction in
braking force, then the tire can slip out under lateral force.
Quoted message said:Quoted message said:Quoted message said:#3) And to clarify, are you saying we should not use any rear brake at
all when we want to reduce speed rapidly in a straight line?
There is strong argument that the rear brake is not required at all when stopping in a straight
line on clean dry pavement.
Sure. Tell that to the guys who race for a living.
Someone has already be beaten me to it. Keith Code has made his living teaching bike handling skills
to motorcycle and bicycle racers. He has also written a book about bicycle racing technique called,
"A Gear Higher: The Bicycle Racer's Handbook of Techniques". A chapter of this book is devoted to
braking. Here are a few excerpts from that chapter about the use of the rear brake in road racing:
"Weight Factor: The single most important factor to be aware of in braking is the weight transfer
that occurs when the brakes are applied. Let's say you are a 160-pound rider and you have a 20
pound bike. During neutral acceleration with even pedal speed and flat surface conditions, weight
distribution at the wheels is roughly forty-five percent front and fifty-five percent rear. A
routine non-aggressive, brake application transfers about seventy-five percent to the front
wheel, leaving around twenty-five percent on the rear. The front end now weighs three times what
the rear does.
"At racing speeds, weight transfer from the increased stopping force is greater still: ninety
percent or more of the weight can transfer to the front, leaving ten percent or less remaining on
the rear. The rear tire, at the ground, now weighs eighteen pounds or less! Obviously, the rear
brake can only slow or stop eighteen pounds worth of you and your bicycle. The lion's share of the
braking (162 pounds) can only be done with the front binder.
"Rear Brake Overuse: Overusing the rear brake is so common as to be almost a fact of life. On the
road, many riders have essentially given up using it for really hard braking. It requires maximum
attention, especially when it causes the rear end to hop or slide.
"On the road, both sliding and hopping render the bike out of control. You can't feel good about
leaning into a turn if you are basically out of control with one of the two points of contact with
earth gone. Even on dirt, a locked rear can be and often is overused as a tool for slowing and
positioning the bike for a turn. Basically, you are stuck on a sliding mass of meat and metal that
only wants to go straight - probably straight into what the rider didn't want to hit! The front is
where the weight and the stopping are
- not the rear."
So the expert, Keith Code, is saying that the front brake is the primary brake all the time, and
that under the heaviest braking, the rear probably shouldn't be used at all. If you truly believe
otherwise, perhaps you should open your own school of performance riding and write your own book.
Quoted message said:You should do the comedy circuit because you've got some hilarious mateerial here!
Not nearly as comedic as your continual scoffing despite not having evidence to support your
position, in addition to continuing insistence that you can brake beyond the physical limits of
a bicycle.
Quoted message said:Quoted message said:If you're rear wheel was skidding, you were over-braking the rear, and should have let up on the
rear brake and increased the front brake. Then perhaps you wouldn't have crashed at all.
Any more front brake and I wouldn't be able to steer and I would probably have gone over the bars
sooner. I was going to hit one of the guys but I slowed as much as possible before doing so. There
was no harm in skidding the rear wheel except for the tire damage. You really don't understand
what's most important in that situation.
Why couldn't you steer with more front brake? The harm in skidding the rear wheel is that you
decrease steering control if the rear wheel is skidding instead of rolling, while at the same
time adding no significant braking with that wheel. After all, wasn't it a skidding rear wheel
that brought Beloki down? Perhaps you wouldn't have crashed at all if you had relied more on your
front brake.
Quoted message said:
Quoted message said:Your braking example is interesting one (28mph to 5mph in 30 feet). Not because it shows your
mastery of braking, but because it shows your poor estimation of your braking capacity. Going from
28mph to 5mph in 30 feet on a standard upright bicycle is essentially impossible. It would require
a uniform deceleration rate of 0.85 g, impossible to achieve on an upright racing bike.
Deceleration from 28 mph to 5 mph would take a minimum of 50 feet at the limit of braking
(1/2g).
There was a very slight uphill, and perhaps I was still going 6.2 mph when I made impact.
A deceleration from 28mph to 6.2mph in 30 feet still takes a deceleration of 0.83 g. Even going up a
5% grade only increases your stopping limit to about 0.57 g - so you still can not have done what
you claim.
Quoted message said:My computer showed 28-5. And how can you calculate my stopping time or distance if you don't know
what tire compound I use, the inflation of the tires, the size of the contact patch, my amount of
weight shift, the road surface or grade, etc.? You don't even know what you don't know.
You gave your initial and final speeds plus distance (28mph to 5mph in 30 feet) which is all that is
required to determine deceleration rate:
Accel. = [(End Speed)^2 - (Start Speed)^2]/[2*(distance)]
This relationship holds whether it is a bicycle, an airplane, or the lunar lander. Tire compound,
inflation, etc. are not only not required to determine the deceleration rate to change velocity
within a given distance, they don't even determine a bicycle's maximum stopping power on clean dry
pavement. Since you are such a great bicycle rider, I'm sure you know that it is impossible to skid
a front tire while braking in a straight line on clean dry pavement. In those situations, the front
tire has far more traction than you can use for braking.
Quoted message said:Quoted message said:Quoted message said:#4) One more question "BikeRacer". How many road or criterium races
have you done Cat 3 or higher?
An interesting question, but completely irrelevant to the discussion.
No it's not. It's guys just like you with all their theories who do not fully understand the real
world application of those theories simply because you lack enough real world experience to make
an accurate assessment.
Just how do you know how much real world experience I may or may not have? Do you naturally assume
that the more one understands about science, the less then understand about practical applications?
If so, you are very, very mistaken. I, and others who understand braking, have plenty of real world
experience, both in races, and actual "real-world" situations such as mountain descents and
emergency traffic avoidance.
Quoted message said:Mark, how many criteriums have you done Cat 3 or better?
As I mentioned before, this question is irrelevant. But since you continue to insist in asking - I'm
afraid that I have lost count of the number of criteriums I have raced with cat. 2 & 3 riders, but I
have done my share. Enough to know that such races are primarily won on the strength of a
competitors legs, hearts and lungs, and to a much lesser extent on bike handling skills; and enough
to know that achieving cat. 2 or 3 status is far from a guarantee of good handling skills.
So far your argument has been mostly ad hominen attack, and little actual evidence to back up your
position (other than your criterium emergency braking example of questionable accuracy, where you
ended up crashing anyway.). It seems you are trying to win this argument with pure bluster. If so,
you are doing a rather poor job.
Mark McMaster [email hidden]
