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Old 05-07-2013, 07:40 PM   #61
snoman002
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Not to dive in the conversation as I know little, but I was surprised a few years ago by a graph showing cornering force and braking force. Think braking on the X axis, cornering force on the Y axis. Above 0 on the X axis was brake force, below acceleration, left on the Y was, well, left and right, well, again, right. The surprising part was that peak deceleration happened not at zero cornering force but actually more deceleration happened with a touch of cornering. In a nutshell, the graph was heart shaped.

My only conclusion was that on the track where brakes can easily lift the rear tire, a bit of cornering actually kept the rear tire down on the ground, allowing greater braking. Deceleration then decreased as cornering increased, likely just due to available traction for attempting both braking and cornering. IIRC the cornering force was fairly high before brake force was equal to what could be done in a straight line.
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Old 05-07-2013, 09:03 PM   #62
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Originally Posted by shaddix View Post
The only advantage I ever heard that is against tipping in with the brakes on is that it is easier to save a slide if you're leaned over on the throttle than if you're leaned over on the brakes.

Anyone like to have a go at that one? Of course a surface hazard won't matter the front will slide regardless, but if the road is just slippery in general and you're barely holding on without knowing it, we would prefer to be on the throttle if and when it breaks loose.

19 years on the road I have run into that all of once, I wasn't on the brakes and I couldn't save it.

Apparently some truck dumped transmission fluid all over a parking lot entrance, so 10 mph no lean coasting behind the car in front of me and the front and washed.
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Old 05-08-2013, 01:19 AM   #63
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Originally Posted by shaddix View Post
The only advantage I ever heard that is against tipping in with the brakes on is that it is easier to save a slide if you're leaned over on the throttle than if you're leaned over on the brakes.
I suppose if you lack the ability to transition from brake to throttle, then yes, there would be a problem. The primary learning required to competently trailbrake is to transition from brake to throttle at the correct time and in the correct manner. Basically, a combination of muscle training and judgement call training.

snoman - you are referring to Kamm's Circle or the traction circle. You have it sideways, though - typically acceleration is up, braking is down, and steering is left and right. The effect you are describing requires significant dialing in of rubber compound, surface preparation, and bike geometry - ie - only in the lab or on the simulation software. Too much change in the real world, even on the track.
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Old 05-08-2013, 11:45 AM   #64
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As far as "NEVER brake in a corner" the Idaho/Oregon program does address trail braking in corners. Simply by mentioning it in the classroom with "You can do it. It's called trail braking. It's an advanced technique generally used to increase speed."
You'll have to show me that page in the Oregon BRT Instructor Guide; it appears to be missing in my copy. Ahem.

I'll take your word for it in Idaho.

We (Oregon) do tell students they can brake in a corner, discuss tractions limits, consequences, and the need to be careful if they find themselves in that position.
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Old 05-08-2013, 11:55 AM   #65
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Originally Posted by atomicalex View Post
I would love to see the MSF change a bit to say something like this...
Grok Dunning-Kruger? Apply to every MSF student. They don't know enough to know that they don't know enough to effectively judge whether they're good enough to trail brake.

Add to that the fact that quite a lot of them are going to wind up on bikes that have- let's face it- less than stellar lean angle and suspension components.
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Old 05-08-2013, 11:59 AM   #66
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Originally Posted by dwoodward View Post
You'll have to show me that page in the Oregon BRT Instructor Guide; it appears to be missing in my copy. Ahem.

I'll take your word for it in Idaho.

We (Oregon) do tell students they can brake in a corner, discuss tractions limits, consequences, and the need to be careful if they find themselves in that position.
Apologies: Oregon actively teaches it in the classroom while Idaho less actively teaches it.

Reason for us is that you can get sucked down the rabbit hole so don't stick your head in very deep...you know, students and what they know and think they know...that sort of thing...you know.
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Capt Crash screwed with this post 05-08-2013 at 12:09 PM
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Old 05-08-2013, 12:45 PM   #67
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I remember watching Fast Freddy Spencer and Jason DeSalvo backing it in, turning and braking to a stop on their knees at the apex of a left hander corner 10 feet away from me. Trail braking for me means my brake marker is deeper into the corner lengthening the straight and that the geometry of the chassis is sharpened as the forks compress making the bike less stable and easier to turn - to put down quick laps and pass other riders I have to trail brake. Releasing the brakes before corner entry can extend the forks just at the wrong time making the bike run wide at the apex. Whichever way you do it being smooth on and off the brakes and smooth with throttle application will help with geometric stability and safety.
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Old 05-08-2013, 01:48 PM   #68
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Originally Posted by atomicalex View Post
snoman - you are referring to Kamm's Circle or the traction circle. You have it sideways, though - typically acceleration is up, braking is down, and steering is left and right. The effect you are describing requires significant dialing in of rubber compound, surface preparation, and bike geometry - ie - only in the lab or on the simulation software. Too much change in the real world, even on the track.
I may have it sideways, but I do remember it was from an accelerometer strapped to a motorcycle, ridden on a racetrack by and experienced rider, not a lab result
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Old 05-08-2013, 07:15 PM   #69
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You'll have to show me that page in the Oregon BRT Instructor Guide; it appears to be missing in my copy. Ahem.

I'll take your word for it in Idaho.

We (Oregon) do tell students they can brake in a corner, discuss tractions limits, consequences, and the need to be careful if they find themselves in that position.
That is new, I've been to the BRC once and the ERC no less than 4-5 (military requirements) times, each time was the same, no breaking and turning, four fingers, no covering yada yada.
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Old 05-08-2013, 10:30 PM   #70
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That is new, I've been to the BRC once and the ERC no less than 4-5 (military requirements) times, each time was the same, no breaking and turning, four fingers, no covering yada yada.
Yeah, the ERC I took on base two years ago covered all of that. Less of a chance for education and more of an observation of your riding skills.
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Old 05-08-2013, 10:36 PM   #71
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Originally Posted by snoman002 View Post
I may have it sideways, but I do remember it was from an accelerometer strapped to a motorcycle, ridden on a racetrack by and experienced rider, not a lab result
To wit, an expert rider in a rather controlled condition. Back before we had fancy computers, we called that a simulation.

<-- friction scientist
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Old 05-08-2013, 10:54 PM   #72
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To wit, an expert rider in a rather controlled condition. Back before we had fancy computers, we called that a simulation.

<-- friction scientist

Interesting, I started putzing around with trying to model a an entire vehicle's effects on friction......and gave that up relatively quickly.
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Old 05-09-2013, 01:19 AM   #73
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Depends on tyres as well.

The K60's I'm using now have more grip leaned than upright - which makes 'going in too fast' much less of a problem than it used to be.
Just grow some and lean it over solves most problems.


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Old 05-09-2013, 12:45 PM   #74
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Interesting, I started putzing around with trying to model a an entire vehicle's effects on friction......and gave that up relatively quickly.
It's ok, most people do. If you want to chat about tribology, I suppose we could head off to Inmates or such.
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Old 05-09-2013, 01:21 PM   #75
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It's ok, most people do. If you want to chat about tribology, I suppose we could head off to Inmates or such.
You've got enough letters behind your title that if you told me that the sky was really green I probably wouldn't argue...
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