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 Threshold Braking
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James R. Davis
Male Administrator
17396 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 07/12/2022 :  5:19 AM Follow poster on Twitter  Join poster on Facebook as Friend                        Like
Recently an attorney asked me to explain 'effective braking' by a motorcyclist. He knew nothing about motorcycles and when I told him that motorcycles have two braking systems (front and rear), he became agitated when he realized that understanding how best to use their brakes, motorcyclists simply might not know.

So, I presented him a part of a report I'd written in the past that discussed 'Threshold Braking' and I think our readers here might appreciate what was in that report as well as him.
---

Effective Braking

A deceleration rate of 1.0G means that speed is being reduced by 32.17 feet per second each second the object is moving. For the layman, that means that a vehicle slowing at a deceleration rate of 1.0G is scrubbing speed by almost exactly 22 MPH every second it is slowing.

Almost any motorcycle can achieve a deceleration rate of nearly 1.0G with normal tire tread and normal brakes on a level and dry roadway. Plaintiff's motorcycle was capable of decelerating at a rate of nearly 1.0G.

Traction is what determines how much braking pressure can be used in order to slow a vehicle's motion. Traction is a function of a tire's rubber quality and tread and the Coefficient of Friction (CoF) of the roadway's surface. A given motorcycle can, for example, slow more quickly on a concrete roadway than it can on an asphalt roadway, because concrete has a higher CoF than does asphalt. Roadway surfaces actually have two different Cofs at the same time. The first is known as the Riding or Rolling CoF and is higher than the second, which is known as the Sliding CoF.

The graphs below show the dynamics involved during braking for a typical roadway. This discussion and the following graphs are intended only to explain the dynamics of proper braking of a motorcycle and do not purport to be exactly representative of the actual CoF values at the scene of any particular incident. The first graph shows that if sufficient braking force is applied to generate any deceleration rate below 1.1G's, that roadway will allow the vehicle tires to continue rolling. If the deceleration rate were to reach 1.1G's, however, then the tire would immediately begin to slide (skid), and the deceleration rate of the vehicle would fall to about 0.825G's as that tire continues to skid along the surface. A rolling vehicle thus can decelerate more quickly than can a skidding one.



If braking is done too aggressively and results in a deceleration rate equal to 1.1G's, then this is what happens:



Appropriate braking (best practices for fastest slowing) is called Threshold Braking. It involves applying enough braking pressure to get anywhere above 0.825G's but below 1.1G's.


Eagle Six
Junior Member
52 Posts


Snowflake, Arizona
USA

Kawasaki

ZX14R

Posted - 07/12/2022 :  8:15 AM
Good stuff James, Thank You for sharing and Thank You for putting the illustrations together. There are many riders I have met that have never experienced 1g braking (or acceleration). Threshold Braking is just a term they have heard but don't understand the application and intermix it with emergency braking. I have attended three advanced skills courses over the years that explore the practical application of threshold braking (which is good)(not MSF courses), but lack explaining the science in-depth (which is bad). Even the best of classes I have attended are challenged with time constraint effecting the choice of what is included in their curriculums!

Curious question, did the attorney understand your explanation to the point he could use it effectively?
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James R. Davis
Male Administrator
17396 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 07/12/2022 :  9:09 AM Follow poster on Twitter  Join poster on Facebook as Friend  
I apologize that I did not post the right graphic for the third chart earlier. Clumsy keyboarding.

As to your question...the attorney understood it just fine. He knew that I would present the concept during deposition and during trial so he only had to ask the 'right' questions.
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Eagle Six
Junior Member
52 Posts


Snowflake, Arizona
USA

Kawasaki

ZX14R

Posted - 07/12/2022 :  12:26 PM
Thank You for cleaning up the graphics. It seems the attorney paid attention in lawyer school, never ask a question you don't already know the answer, and if you know the right answer, ask the right question!

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scottrnelson
Advanced Member
6960 Posts
[Mentor]


Meridian, ID
USA

Honda

XR650L, 790 Adv R

Posted - 07/13/2022 :  2:36 AM
I hope I'm not derailing the discussion with this...

Just yesterday I was reading another great Kevin Cameron article about motorcycle steering heads and the forces that they have to deal with. That article is here: https://www.cycleworld.com/story/bl...d-explained/

I found out that the MotoGP bikes can achieve up to 1.45G of deceleration and that the top riders hover the rear wheel just barely off of the pavement when slowing from high speed to a much slower corner. Not something any of us should be trying, just something I didn't know before. Those guys are right at the edge of the top line on the graph. Also, their tires have something to do with maximum braking achievable, not just the road surface. When they're warmed up they get better traction, but start losing some of it toward the end of the race when they start to wear out.

Here's a photo from that article of Fabio Quartararo, last year's champion, doing it coming into a corner. It's not so obvious watching in real time, but some slow motion shots have the rear wheel in the air for quite a long time.
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James R. Davis
Male Administrator
17396 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 07/13/2022 :  5:58 AM Follow poster on Twitter  Join poster on Facebook as Friend  
Fascinating information and extreme skill evidenced.

This thread is not about how to do threshold braking or how to be the most effective brake operator, just that braking is not just 'squeeze' and 'step' pressures. Threshold braking is, as you said, making your bike act like it has ABS, or being more conservative than that and just making it slow faster than it would when skidding. It is important that our readers NOT think that threshold braking means trying to get as close to a skid as possible!

Apparently, you are a true student of the sport. You know, for example, that effective braking also includes masterful control of body posture to take advantage of air flow (turbulence) in order to add or remove weight and, thus, traction. (An interesting aside--if your bike, including you, weighs 800 lbs. at zero MPH, it typically weighs about 750 lbs. when moving at 75 MPH.)

This site was designed to educate our readers to the end of increasing their odds of surviving our sport, not winning. Winning involves compromizing safety. I leave that to racers, not street riders.

Great picture!

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Eagle Six
Junior Member
52 Posts


Snowflake, Arizona
USA

Kawasaki

ZX14R

Posted - 07/13/2022 :  12:03 PM
Thank You Scott for posting the article, photo and your comment.

At the risk of sliding this thread farther from center.....(and it's a bit long as well)

During any type of brake training whether than be beginner (MSF) type or more advanced high speed threshold skills, my concern is the difference between typical training scenarios (parking lot or track based) as compared to the reality of an obstruction and how that psychologically/physiologically effects our skills in the real world.

I have had several threshold training schools at speed. I, solo, and 2-up with my wife, self-train (practice) threshold braking regularly (at least every other month, sometimes monthly). My reaction during school training and during our self-training is different than the few times I have actually used threshold braking to avoid a collision.

Once when an SUV suddenly obstructed my path, and once with a full size dead bull obstructed my path. Both times I used threshold braking, both times I stopped with lots of safe space between me and the obstruction. I credit that safe distance to three aspects. 1) my threshold training and recurring self-training. 2) I was at speed, but not excessive speed. 3) I was prepared to stop if surprised.

Nonetheless on both of these occasions my fright meter was pegging towards the maximum. If any of these 3 were missing I may not have ended with that safe distance and might have experienced a collision.

I have never felted alarmed about stopping in a short distance while training when there is no harmful penalty if I fail. I have never had any training that presented an obstruction similar to reality. I have thought about methods of simulation and have never come up with anything practical and safe that would be covered by liability insurance.

Bottom line of this is, there is a sizable difference between threshold braking skills to a safe stop during skills development training than when we are facing a large obstruction that will hurt us if we don't get stopped to avoid it, and most of that difference is between our ears. Regardless, I continue to train and use visualization techniques to edge closer to reality based training.

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scottrnelson
Advanced Member
6960 Posts
[Mentor]


Meridian, ID
USA

Honda

XR650L, 790 Adv R

Posted - 07/13/2022 :  4:11 PM
Occasionally when riding on dirt roads, I have to slow by quite a bit when the road turns and I have picked up a bit too much speed on the straight parts, or I'm headed downhill. Usually I'm on loose stuff like in the photo below. There is typically about an inch of dirt and or gravel on top, so there isn't a whole lot of traction available. To slow down in those conditions I try to be fairly even with the front and rear brakes, with a slight bias toward the front. This might take me to the side of the road a bit until I get slowed enough because steering doesn't really do much on dirt like that. In other words, the bike tends to go straight until it has dropped enough speed to turn.

I'm guessing I barely hit 0.2G of deceleration in those conditions. I'm not sure if this is directly relevant to threshold braking on clean pavement other than that it's one more situation where I'm trying to figure out how much braking I can get away with without sliding the front tire. It doesn't really matter much if the rear slides or not. On my Honda XR650L, there is no electronic assist to the braking, but the KTM has ABS and a mode that is supposed to know what to do in off road conditions. I still don't trust ABS to save me, though.

When riding on the street my goal is to pay attention to what's ahead so that I never come close to threshold braking. On dirt, sometimes it's necessary to get closer to the limit.

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Eagle Six
Junior Member
52 Posts


Snowflake, Arizona
USA

Kawasaki

ZX14R

Posted - 07/14/2022 :  9:57 AM
Scott, are there times in some turns when you slide the rear tire to turn, rather than slowing to steer with the front? It's been over 15 years since I have been on serious dirt/trails and even then I rode a dirt bike just enough to be dangerous! In a lot of turns I would throttle to break the rear loose and slide a bit to get direction in the turns. I don't remember ever threshold braking on dirt, but maybe that is in part why I fell over now and then. Also I have never ridden a heavy adventure bike on trails. I do ride my street bike on dirt that is well graded but that is easy stuff.

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scottrnelson
Advanced Member
6960 Posts
[Mentor]


Meridian, ID
USA

Honda

XR650L, 790 Adv R

Posted - 07/14/2022 :  1:16 PM
quote:
Originally posted by Eagle Six

Scott, are there times in some turns when you slide the rear tire to turn, rather than slowing to steer with the front?
In theory, you can do that, but I haven't been able to reliably do it on the dirt that we have around here. There is one dirt road in the area that gets wonderful traction right after a rain where it kind of works when heading uphill, but generally I don't get good enough front tire traction anywhere else to still be able to steer if the rear is sliding.

I've read up on the subject and watched videos about it, but can't get it to work, so I've gone back to what works well for me. I just go slower in the turns and keep the bike as upright as possible. And try to avoid situations where I have to do any serious braking right before a turn...
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rkfire
Advanced Member
1719 Posts


Stratford, CT
USA

Suzuki

Bandit

Posted - 07/14/2022 :  1:55 PM   Join poster on Facebook as Friend  
quote:
Originally posted by Eagle Six


During any type of brake training whether than be beginner (MSF) type or more advanced high speed threshold skills, my concern is the difference between typical training scenarios (parking lot or track based) as compared to the reality of an obstruction and how that psychologically/physiologically effects our skills in the real world.



Nonetheless on both of these occasions my fright meter was pegging towards the maximum. If any of these 3 were missing I may not have ended with that safe distance and might have experienced a collision.

I have never felted alarmed about stopping in a short distance while training when there is no harmful penalty if I fail. I have never had any training that presented an obstruction similar to reality. I have thought about methods of simulation and have never come up with anything practical and safe that would be covered by liability insurance.

Bottom line of this is, there is a sizable difference between threshold braking skills to a safe stop during skills development training than when we are facing a large obstruction that will hurt us if we don't get stopped to avoid it, and most of that difference is between our ears. Regardless, I continue to train and use visualization techniques to edge closer to reality based training.





I too practice threshold braking, but mostly to get that muscle memory and the overall feel of the hard braking.

I just rely on that.

I had one real scare some years ago and talked about it on this site. For this discussion, I think it worth noting that during that scare, I was thinking.....minimize my crash speed as much as possible. (I didn't crash but there was a scant few feet left to the impact)

I think one other thing of note in my situation. I actually braked harder than I ever practiced. The urgency, the adrenaline, got me squeezing just a little more.
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Eagle Six
Junior Member
52 Posts


Snowflake, Arizona
USA

Kawasaki

ZX14R

Posted - 07/14/2022 :  2:54 PM
I think it would be expected to brake harder when something large and harmful is in our path than when we are training or practicing. Good that you stopped short and held it under control.

I should add, when I am threshold braking, I'm not braking/slowing/stopping by the definition of threshold braking with my current bike. There is no way to turn off the ABS or cornering computer. So, maybe I should call it practicing threshold ABS braking!!!

My previous bikes didn't have ABS and I could slip both front and rear tires to feel the force I needed to fall just short of the slip (but even that is not threshold braking by definition). But unless we can slip the tires how do we know where the threshold is? Even then with so many variables I would get it sometimes or other times not. Perhaps we play a little loose with the term threshold. I welcome other opinions on this. I bet somewhere on this forum James has discussed it.


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James R. Davis
Male Administrator
17396 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 07/14/2022 :  6:39 PM Follow poster on Twitter  Join poster on Facebook as Friend  
A couple of important points to consider ...

As I've said before, threshold braking should NOT be thought of as attaining as close to a skid (or ABS-like) as possible. Instead, it should be thought of as being able to reliably achieve a deceleration rate that is greater than what you get if skidding. It is DANGEROUS to try to get close to a skid.

Second, when you are practicing braking skills, you should do it at close to 30 MPH, NOT FASTER!! The idea is to FEEL the deceleration rate in order to recognize that you are achieving your objective. A 0.85G deceleration rate feels the same at 30 MPH as it does at any other speed, so you gain nothing practicing at a higher speed except more danger.

Finally, as has been shared here already, you can EXPECT that adrenaline will push up your deceleration rate during a reaction to a serious threat. If you attempt to get something like a 0.85G deceleration rate reliably during practice, during a real emergency you can expect to achieve more than a 0.9G rate - for that very reason. Practicing an effort to get a 0.95G rate will with high confidence result in skidding during a panic stop attempt!!!!
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Eagle Six
Junior Member
52 Posts


Snowflake, Arizona
USA

Kawasaki

ZX14R

Posted - 07/14/2022 :  6:45 PM
Thank You James good stuff.
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James R. Davis
Male Administrator
17396 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 07/14/2022 :  6:51 PM Follow poster on Twitter  Join poster on Facebook as Friend  
One more thing ...

Studies have suggested that most riders SELF-LIMIT their braking efforts to about 0.8G's. No idea how accurate that assessment is, but the explanations include
1) Fear of being tossed over the handlebars
2) Having experienced a skid, they want to slow down without a skid

So, if you practice threshold braking in an effort to reliably achieve a deceleration rate of 0.85G's, you are CERTAINLY learning how to stop more quickly than most riders even believe they can safely do so.
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rkfire
Advanced Member
1719 Posts


Stratford, CT
USA

Suzuki

Bandit

Posted - 07/14/2022 :  7:04 PM   Join poster on Facebook as Friend  
My current bike has ABS and is the first bike I have had it.

For my money, ABS is a great advantage to practice threshold braking, in that I practice braking hard up to but not beyond the point of engaging the ABS system.

ABS engages when sensing the tire is not rolling, so if I avoid engaging it I am close.

I think, I am braking harder and shorter than if ABS is engaged. I'd rather leave the ABS to do it's thing in the wet or slippery conditions.

One other oddity on this BMW is the telelever front suspension. Supposed to having less brake dive than regular forks, I personally prefer regular forks and after all these years, the fork dive seemed to be part of my feel for braking hard.
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James R. Davis
Male Administrator
17396 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 07/14/2022 :  7:29 PM Follow poster on Twitter  Join poster on Facebook as Friend  
I've been an IT specialist in one form or another for more than 60 years (since 1961). You'd think that I would trust electronics with my life more than I do. Wrong!

When ABS first appeared on motorcycles, I was dead set against it. The recycle speed (deactivation to activation of the brakes) was far too slow for me and I saw many tests where good braking skills outperformed ABS in real life. But recycle speeds have increased dramatically and that is no longer my concern.

What concerns me more is that tests have shown that ABS works badly while traveling in other than a straight line.

However, I agree with what was just said...ABS is almost magical in effectiveness over a non-trained, lower experienced rider who doesn't practice braking skills. And it's the wet spot or ice or bit of oil/grease on the roadway that proves the life-saving advantage of ABS for almost anybody. So, I, too, advocate having a bike equipped with ABS.

When self-driving automobiles become plentiful, count me out! I believe in the efficacy of an alert, trained mind with experience over any form of electronics. Besides, I like to be in control.
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scottrnelson
Advanced Member
6960 Posts
[Mentor]


Meridian, ID
USA

Honda

XR650L, 790 Adv R

Posted - 07/15/2022 :  8:14 AM
quote:
Originally posted by James R. Davis

What concerns me more is that tests have shown that ABS works badly while traveling in other than a straight line.
Many of the newer bikes have lean angle sensors and can adjust the ABS behavior when in a turn. My 2020 KTM has it. Not that I would trust it, though.
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Eagle Six
Junior Member
52 Posts


Snowflake, Arizona
USA

Kawasaki

ZX14R

Posted - 07/15/2022 :  11:11 AM
My current Ninja has ABS, Traction Control, Intelligent Anti-Lock Brakes, lean Angle Indicator, Cornering Management Function, IMU Enhanced Chassis Orientation Awareness, Assist & Slipper Clutch, and Quick Shifter up and down.

My previous two Ninja's one had traction control and the other nothing. I felt safer on either of these two than my current and I challenge the current far less than I did the previous two. I think this is in part my distrust of what I cannot see, feel, or adjust! Of course there is the getting old thing as well.
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James R. Davis
Male Administrator
17396 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 07/15/2022 :  2:18 PM Follow poster on Twitter  Join poster on Facebook as Friend  
Amazing set of electronic advances were just described. More power to you and my best wishes.

Still, it makes sense to me to practice threshold braking and leave the ABS and other electronics to saving your life if you make a mistake. You just might be skillful enough to never need it.

About all the magical electronics that are finding their way into vehicles ...

Did you know that when/if you get into a serious accident when driving a vehicle that has nav/information (navigation/radio/telephone) technology installed the police can EASILY determine WHERE you've been over the previous 10 days, WHO you've called and WHO has called you over that same time frame, the TELEPHONE NUMBER on both sides of those calls, the GEOGRAPHIC LOCATION of both sides of those calls, your CONTACT LIST, what radio stations you listen to, (and POSSIBLY what WEB SITES you visit), HOW FAST you were traveling at the time of impact, what your DECELERATION RATE was both lateral and longitudinal (brake usage and skid/slide) for some time before the impact, any and all vehicle MALFUNCTIONS and warnings (time for maintenance needed), and whether or not you drank coffee that morning?

OK, your vehicle doesn't (YET) test your breath or blood for coffee or drugs, but you get the point.

Oh, a warrant isn't needed to access all of that information!!! Your dealership can get it in less than five minutes even without a collision. Do you think your wife/husband/boyfriend or girlfriend/ mother/father/drug dealer/employer/bank/IRS/police etc. might be interested?

Could ANYBODY be interested in how close to the capital you (or who you interact with) was on January 6th?

Have you ever heard of the Internet of Things (IoT)? Do you honestly believe that Google or some other organization hasn't made or isn't planning on getting that information remotely as soon as possible? Do you think that the police might be interested in causing your vehicle to slow/turn/stop on command?

Ain't electronics grand?
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Eagle Six
Junior Member
52 Posts


Snowflake, Arizona
USA

Kawasaki

ZX14R

Posted - 07/15/2022 :  5:29 PM
That is the main reason I am not interested in navigation systems or newer vehicles equipped with them. You cannot control features nor can you turn it off. The same with 99.99% of smart phones (I made up that percentage, but think it is pretty close!). Big brother is watching.
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