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Niebor
Ex-Member

Posted - 07/26/2009 :  8:18 PM                       Like
Three of us met today in Colorado Springs, intent on working a braking skills challenge. This challenge had a little twist. Instead of trying to see how fast we could stop, the focus was keeping peak braking level below given thresholds. We made some very interesting observations. Among them was that our practical limit with no lockup was about .7g. We worked out in the range of 2.5 to just over .7gs. All three of us were very comfortable at .5gs. When we neared .7 each of us either had a lockup or felt lockup was impending. Indeed, one each; front, rear, lockup impending. The front lockup appeared to be induced by a roughly 3/8 crack in the pavement.

What I rode off with: It seems far more important we focus on early recognition and slow braking, rather than personal best for braking threshold. By challenging myself to average under .3, and to consider .5g utter failure, I give myself a much greater margin.

Thoughts?

rayg50
Male Moderator
2082 Posts
[Mentor]


NYC, NY
USA

Honda

Shadow Spirit 750DC

Posted - 07/26/2009 :  8:55 PM
quote:
Originally posted by Niebor

... We worked out in the range of 2.5 to just over .7gs...

Thoughts?




Thoughts no, questions yes. Above did you mean .25?

Never having seen a challenge, I can't quite picture the challenge. Did you pick a stopping point and then begin to apply the lower degree of pressure to stop before that point? In other words were you trying to figure out at what point (how far from the target) you needed to begin .3g in order to stop in time. If it turned out that you needed .5 then you failed to judge the distance?

I guess if you could give me the mechanics of the challenge I might have some thoughts. What the heck I will throw in a thought based upon my version of the challenge.

If I were comfortable with .3 and I had a good measure of the distance it required to stop then I could use that as a following distance or a scanning distance rather than the 2-4-12 second "rule". Anything at or beyond that distance (and it would vary based on mph and road conditions) would be a threat avoidable by braking with no fear of locking my brakes. Not to say that anything within it would be unavoidable.

Ray

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Niebor
Ex-Member

Posted - 07/26/2009 :  9:24 PM
quote:

Thoughts no, questions yes. Above did you mean .25?


Indeed, that was a typo. I did mean .25, and I should have stated .2 as our goal
quote:

Did you pick a stopping point and then begin to apply the lower degree of pressure to stop before that point? In other words were you trying to figure out at what point (how far from the target) you needed to begin .3g in order to stop in time. If it turned out that you needed .5 then you failed to judge the distance?


Yes, We estimated at .2g we would stop in 66'. We set a cone at 66' and stopped at the .2g threshold according to the g-meter. As it turned out, it was very close to 66'. We did the same for .3 through .5 distances.

quote:

If I were comfortable with .3 and I had a good measure of the distance it required to stop then I could use that as a following distance or a scanning distance rather than the 2-4-12 second "rule". Anything at or beyond that distance (and it would vary based on mph and road conditions) would be a threat avoidable by braking with no fear of locking my brakes. Not to say that anything within it would be unavoidable.



No, not .3, .2 is our goal in traffic. And no, your still forced to scan ahead at least 12 seconds, greater yet if you intend to remain under .2.
Lee
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rayg50
Male Moderator
2082 Posts
[Mentor]


NYC, NY
USA

Honda

Shadow Spirit 750DC

Posted - 07/26/2009 :  10:34 PM
I may have to chew on this one a bit. I am still not quite getting it. What was your speed at the time you started braking?

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Niebor
Ex-Member

Posted - 07/26/2009 :  11:23 PM
Ahh, good call. Sorry for leaving it out. In all cases our speed was about 20 mph, on a standard MSF range braking strip. Any faster and things get spooky in a hurry.

One thing seemed key. If we were very smooth in brake application, many of our .5g peak distances were considerably less than our .7+ attempts, especially those that were less than perfect, as most were. Indeed, the front wheel lockup attempt distance exceeded the measurement range.
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bridwell52
Male Senior Member
377 Posts


Pensacola, FL
USA

BMW

KGT

Posted - 07/27/2009 :  5:05 AM
Did you find that different bikes had different stopping distances under the same conditions?
Why I ask is that my new to me V-strom with good pads has such poor brakes it is unacceptable to me.

David
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bachman1961
Male Advanced Member
2260 Posts
[Mentor]


colorado springs, co
USA

Honda

CB750 NightHawk

Posted - 07/27/2009 :  5:47 AM

Working on smooth braking and stopping in that 66 foot distance was not automatic for me. I had to fight the urge to compete with my earlier runs in tightening up the stopping distance. The object was NOT to upset the travel of the bike in a full on emergency stop. After thinking through some of the benefits of this skill (keeping to .25 on the g meter), it became much easier and muscle memory kicked in. My first few runs had me looking for the end cone in my periphery and soon, the 'feel' of my bike and braking force became much more consistent to the point that I ignored the end cone, yet braked to that same point in those following runs.

We talked about many factors of this skill and points of interest to me were getting to know my bike better, creating the habit of scanning / following distance to allow for safe braking forces, avoiding the surprise reaction to following traffic and keeping within the mid point of the suspension, where traction is at it's best.

The thought here is that if I'm scrubbing the brakes at .3 or more, I've failed the due diligence of proper scanning, following distance or threat recognition. Certainly, there is no discounting the potentials that exist for the small varmints darting out of the shadows or even the large varmints .... from larger shadows.

bridwell52

In my opinion, at these light to moderate forces, these did not, and most bikes will not see appreciable differences in distance. Splitting hairs, the reaction time of the rider, size or compound of the tires / contact patch etc.... sure, there would likely be some variations. As you say, knowing your bike and how if performs is critical.
Did you post your symptoms in the tech / maint thread here to get some input?

~brian

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OB
Male Advanced Member
528 Posts


Houston, TX
USA

Buell

1125CR and others

Posted - 08/01/2009 :  6:05 PM
Lee (Niebor),

I have to admit, your approximation skills are great. I had to calculate the distance for a 0.2 deceleration. From my High School Physics book (no calculus however, they do use the concepts of small increments to approximate sometimes), the following formula applies at a constant acceleration.

distance travelled = d
initial velocity = v
a = acceleration
t = time traveled

d = v*t + 1/2 * a * t^2

using your example of 0.2 g deceleration we get

32.174 ft/sec^2 * 0.2 = 6.4348 ft/sec^2 at 0.2 g

Initial velocity = 20 mph * 88 fps / 60 mph = 29.333 fps

time to decelerate from 20 mph to 0 mph at 0.2 g's shown below:

(29.333 fps) / (6.4348 ft/sec^2) = 4.5585 seconds

Plugging in to first formula to find distance to stop from 20 mph at 0.2 g is as follows:

d (in ft.) = 29.333 * 4.5585 + 1/2 * -6.4348 * 4.5585 * 4.5585
d=66.85 ft (approximately)

Like I said Lee you are a good approximater. I had to calculate it.

So, you got me thinking about what the MSF expects for a standard deceleration on the BRC braking test.

I calculated that to be between 0.51 - 0.61 g for their speed range of 11.86 mph to 18.94 mph

Thanks for the post. It was fun.

// OB

fixed intial speed 20 mpg to 20 mph

Edited by - OB on 08/02/2009 7:01 AM
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bachman1961
Male Advanced Member
2260 Posts
[Mentor]


colorado springs, co
USA

Honda

CB750 NightHawk

Posted - 08/03/2009 :  4:03 AM
quote:
Originally posted by Niebor


...the focus was keeping peak braking level below given thresholds.

Indeed, one each; front, rear, lockup impending. The front lockup appeared to be induced by a roughly 3/8 crack in the pavement.

What I rode off with: It seems far more important we focus on early recognition and slow braking, challenging myself to average under .3, and to consider .5g utter failure, I give myself a much greater margin.

Thoughts?



I had some 'eyes wide open' revelations on that day. One in particular keeps haunting me and that is the paved surface I ride on. This braking drill was a lesson (for me), illustrating the trivial imperfections of pavement and it's potential consequence causing the wheel to go from traction / braking to (skipping over a tiny gap) the wheel lock-up.
The simple solution was the theme for that day on the lot; focusing on lower g force to (as Niebor might say) " give greater margin ".
As I think about those effects and the number of quick stops I see in everyday traffic, I think of the occasional crash where a bike had locked up into a skid ... wondering if it was over input or a nearly invisible imperfection that transferred a heavier g force from traction to the skid. In that event and in either cause, their margin got all used up.
My rides are more relaxed and I find I am more often rolling up to cars and not having to generate much braking force at all.
The braking forces are there beyond what I've been using but the road surface may not cooperate (and I'm not much of a gambler).

~brian
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dhalen32
Male Moderator
842 Posts
[Mentor]


Omaha, NE
USA

BMW

R1200RT

Posted - 08/03/2009 :  6:05 AM
Bachman:
I'll bet that your "eyes wide open" experience with pavement variation probably makes you want to consider ABS on your next motorcycle. It is a feature I look for now when I am shopping for that next bike. Thanks for sharing your thoughts and experiences with us.
Dave
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bachman1961
Male Advanced Member
2260 Posts
[Mentor]


colorado springs, co
USA

Honda

CB750 NightHawk

Posted - 08/03/2009 :  6:26 AM
quote:
Originally posted by dhalen32

Bachman:
I'll bet that your "eyes wide open" experience with pavement variation probably makes you want to consider ABS on your next motorcycle. It is a feature I look for now when I am shopping for that next bike. Thanks for sharing your thoughts and experiences with us.
Dave



Excellent and applicable thought ! I hadn't even considered it until your mention. For the most part, I hope to stay well aware of the difference between .2 g's and something above .5 but things can go awry for sure. This exercise we worked on really hit it home for me ... don't put myself in a position to use up that difference. Too many variables exist to squash the space I think I have. There really are so many things I CAN control and it's my personal responsibility to save myself (often times) from myself. Sure, we hear the other driver in the cage being called all sorts of names but I can't put all my cards in someones else's hand ... it just ain't me and I've learned too many other people can do so without ever looking at it that way.

ABS really sounds like a great tool but by the time (if ever), I get a different bike , I've got lots surviving to do .. with the help my new habits.

~brian

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rtbain
Ex-Member

Posted - 09/02/2009 :  8:41 AM
Braking is very much affected by environment, motorbike and rider skills.

First my philosophy.

Braking is a perishable skill so maximum braking drill should be done at least once a month. When you are learning a new technique or improving an old one work on it every week until satisfied.

Dont worry about G forces. Work on stopping distances. While 20mph is a good place to begin ease the speed up until you are working at real world speeds. Incremental steps are the key here.

Practice
Find a good place to practice. Dont bother asking permission. If the owner of the property is asked they usually say no for liability reasons. Its much easier to get forgiveness than permission. Take a leaf blower along, its a great way to remove debris.

Rather than use cones cut tennis balls in half for markers. You can run over them without incident and they are much easier to carry, cheaper too.

MSF teaches four finger braking. I believe it is a good place to start and for many a good place to remain. Personally I prefer two or three finger braking. If you use two fingers its easy to ride with the brakes covered at all times, granted this takes some getting used to. Try it for a while and see what feels best for you.

In braking exercises smooth is where its at. If you are a shooter think of the break lever as a trigger. You squeeze it. The difference is the rate at which you squeeze. With practice you will soon learn the feel of applying max break pressure in a smooth even pull. Just as important is brake release. Smooth release is important.

So why all the talk about smooth? Well a lot of stuff happens to the motorbike as you apply the brakes. If the brakes are applied abruptly the changes to the motorbikes attitude will be abrupt. Such abrupt changes tend to upset the motorcycle and can cause problems.
-continued-
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rtbain
Ex-Member

Posted - 09/02/2009 :  9:02 AM
So lets begin by setting a speed of 20mph and marking a point where you will begin to apply brakes and a desired stopping point. At this speed you want to work on being smooth and being accurate. In short order you will be able to consistently be able to hit your mark.

An important item here is target fixation. Do not look at your markers. Keep your head and eyes level and use you peripheral vision to note the markers. Using peripheral vision is a learned skill so be patient with yourself. If anyone is interested I have learned some easy drills for increasing peripheral vision.

So practice, practice, practice. Take breaks often, stay hydrated. Have fun. At first I feel its best to work on either the front or the rear brakes. This gives you the opportunity to concentrate on one skill. So lets begin with the rear brake.

In the MSF you are taught to never lock the rear and if you do keep it locked until you come to a complete stop. This is excellent advice for the new rider. But as your skills and experience grow there are exceptions to this rule.

If you are upright and traveling in a straight line you can ease off a locked rear brake. Ease off is the key term here. Remember that sudden moves make the motorcycle angry. If you find yourself with a locked rear tire and are upright and traveling in a straight line eeeease the rear brake off. The rear tire will begin rolling again and you are good.

Turing greatly magnifies the hazards in this maneuver. Regaining traction suddenly while leaned over can lead to a highside. This is where the motorbike regains traction at the rear and throws the rider off the motorbike. Its an ugly, painful way to dismount and should be avoided at all costs. Rear traction can be regained in a turn by easing off the rear brake but it can only be successfully performed by a highly skilled rider who is well practiced. In short its better to ride out the lock up to a complete stop.

Whichever approach you decide is right for you practice. Lock the rear in the practice area and get used to how your bike reacts.
-continued-
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James R. Davis
Male Administrator
17295 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 09/02/2009 :  9:04 AM Follow poster on Twitter  Join poster on Facebook as Friend  
quote:
Dont worry about G forces. Work on stopping distances. While 20mph is a good place to begin ease the speed up until you are working at real world speeds. Incremental steps are the key here.


That may be your philosophy, but it fails to consider safety while practicing. Surely you don't mean that you should practice emergency braking from time to time at 60 or 70 mph (real world)?

The reason you pay attention to G forces while practicing is that you ONLY have 'feel' to gauge your performance when it counts. The 'feel' of decelerating at threshold rates is exactly the same whether you do it at 20 mph or 40 mph or 70 mph. Once you learn what good braking performance is at 20 mph, you know what good braking performance feels like at any speed. While practicing at about 20 mph you have a HUGE margin of safety because if you overdo it and actually lock that front tire (or rear tire) you will already have slowed down (from 20 mph) before the threat of hitting the ground. Indeed, it is possible that you have already come to virtually a complete stop before the bike kisses the ground. That is NOT an available safety margin should you overdo it during practice at, say, 40 mph.

quote:
Lock the rear in the practice area and get used to how your bike reacts.

This is also advice that I cannot support. Indeed, it's my opinion that it NEVER - not once in your lifetime - makes sense to aggressively use your rear brake so that advising someone to deliberately lock their rear brake simply makes no sense to me. When the MSF had an exercise that had students lock their rear brakes and skid to a stop so that the students could 'see that locking the rear brake is not necessarily going to cause a crash' (I know that they claimed it was part of a set of exercises designed to prove that use of the rear brake, only, was less effective than using the front or both, but I was told by more than one instructor that they wanted to show it wasn't all that dangerous as well), they made it OPTIONAL because they knew that that exercise, even at parking lot speeds, was DANGEROUS. They subsequently eliminated that class exercise after some heavy prodding from people like me.
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rtbain
Ex-Member

Posted - 09/02/2009 :  1:54 PM
I most surely do advocate practicing emergency stopping procedures at normal road speeds. I am coming to that point in the next few posts. Still having difficulties with post size.

Unless you have an onboard accelerometer (which by the way my race bike has) you can only use a calculated g-force. Since practice is done in the real world, not on a spreadsheet I feel using calculated g-forces with many unknowns is, well, optimistic. Shoot the differences in motorcycles are enough to skew the calculations. Throw in rider weight, fuel load, tire manufacture, tire pressure, pavement type, condition, temperature and weather and youve got one complicated equation.

Dont get me wrong, I use my accelerometer for tuning purposes. As for estimating g-force, well its asking a bit much of a student. They should be aware of what g-forces are in general, but calculating actual vales with so many variables is unnecessary.

Braking from 60 is a LOT different than braking from 20. ONCE A RIDER SKILLS have passed the newbie mark I heartily encourage practicing emergency braking at normal road speeds. When an emergency arises your performance drops to the lowest level of training. If you have only trianed at 20mph and need to stop from 60mph you are at a disadvantage.

Becoming a proficient motorcyclist is a lifelong endeavor. You are either busy learning new skills or practicing old ones. I look at skills as I would tools in a tool box. It may not be appropriate for this particular job, but I know it if I need it. But that does not mean I should not have it.

I feel I have made it clear that these exercises should be done in a clear location as experience permits. The only way to gain experience is by doing. Reading and calculating will only take you so far.

An analogues situation exists in pilot training. Aspiring pilots used to have to prove proficiency in unusual attitudes. This meant actually stalling an airframe and spin recovery. Some in the FAA felt this was too rigorous and dangerous and eliminated the requirement.

Dumbing down education in motorcycling because something is perceived as dangerous follows this line of thinking. Motorcycling itself is dangerous. The safest rider is the one with the best skill set.
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rtbain
Ex-Member

Posted - 09/02/2009 :  2:04 PM
Locking up the rear brake as a practice maneuver.

James has stated his position clearly. I would like to be just as plain. There are risks to this exercise. There are risks to anything you do with a motorcycle. There is no such thing as the absence of risk.

Risk can only be managed, not eliminated. The rider only has control over some, not all of the variables in the real world. As such the rider must train for as many eventualities as possible.

Inadvertently locking the rear wheel is a distinct possibility. Doing it in a training area under controlled conditions allows the rider to learn skills that allow them to deal with the situation.

In my view is its much better to learn in a controlled environment than on the street. Its very easy to say that one should never lock the rear brake. But it happens. Once it happens what do you do?
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James R. Davis
Male Administrator
17295 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 09/02/2009 :  2:05 PM Follow poster on Twitter  Join poster on Facebook as Friend  
quote:
Braking from 60 is a LOT different than braking from 20.

Hmmm ... other than the existence of more wind, what other differences do you maintain exist?

NOBODY, certainly not me, has suggested that you do any calculating when involved in an emergency stop situation. In fact, I have maintained that you should focus your absolute attention on that task.

You learn what good braking performance FEELS like and THAT translates to good braking performance at any speed.

quote:
The safest rider is the one with the best skill set.

That is also untrue. The safest rider is the one who AVOIDS the most dangerous situations and behaviors.
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rtbain
Ex-Member

Posted - 09/02/2009 :  2:23 PM
quote:
Originally posted by James R. Davis

quote:
Braking from 60 is a LOT different than braking from 20.

Hmmm ... other than the existence of more wind, what other differences do you maintain exist?



How do I stop thee, let me count the ways.
Momentum = Mass times velocity.
More brake lever pressure CAN be required. It definitely must be maintained for a longer period of time.
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rtbain
Ex-Member

Posted - 09/02/2009 :  2:24 PM
quote:

NOBODY, certainly not me, has suggested that you do any calculating when involved in an emergency stop situation. In fact, I have maintained that you should focus your absolute attention on that task.

Instead of trying to see how fast we could stop, the focus was keeping peak braking level below given thresholds. We made some very interesting observations. Among them was that our practical limit with no lockup was about .7g. We worked out in the range of 2.5 to just over .7gs. All three of us were very comfortable at .5gs. When we neared .7 each of us either had a lockup or felt lockup was impending. Indeed, one each; front, rear, lockup impending. The front lockup appeared to be induced by a roughly 3/8 crack in the pavement.



Sounds like somebody is doing some rough calculations here. Nothing wrong with that of course.
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rtbain
Ex-Member

Posted - 09/02/2009 :  2:25 PM
quote:

You learn what good braking performance FEELS like and THAT translates to good braking performance at any speed.



Here I can unequivocally state the above assertion is dead wrong. I run LSR (land speed race) motorcycles. If you brake at 200mph like you do at 20mph you will kiss the pavement.



quote:
The safest rider is the one with the best skill set.

quote:

That is also untrue. The safest rider is the one who AVOIDS the most dangerous situations and behaviors.



Its not untrue just because you dont agree with it. Some situations are unavoidable. Truck running a red light. A deer dashing onto the road.
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galileo
Ex-Member

Posted - 09/02/2009 :  2:49 PM
Personally, I'm not in favor of practicing threshold braking from speeds greater than about 20 mph. If I ever have to brake from 200 mph, I'd consider that a serious mental lapse.

True threshold braking has a very high probability of a skid. Telling someone to practice is tantamount to suggesting they skid even though we tell them not to. At speeds up to 20 mph, this isn't serious as the speed the skid actually occurs is pretty slow and a drop would be even slower.

If someone wants to practice firm braking from higher speeds, that's fine. I'm talking about what one might use for a yellow light where they stop kind of late. And even then, I'd be careful not to push it quite that far. But threshold, no way. I'm not going to place myself at a high risk of a crash today to avoid a possibility that may not even arise in the future.

Using your logic, I'd also practice running off the road at 75 mph. I have practiced it in a carefully controlled environment at slower speeds.

Personally, I think people overdramatize the motor skill sets required to avoid a crash. If they were high, riders could never make it through the first year. Matching riding habits to skill sets is much more important in my opinion.

The thread started off with:

"What I rode off with: It seems far more important we focus on early recognition and slow braking, rather than personal best for braking threshold. By challenging myself to average under .3, and to consider .5g utter failure, I give myself a much greater margin."

Meromorph pointed out this is "undramatic braking."

Maybe you could put your g-meter to use practicing this.

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