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Jaybird180

TC Rule #2 and Braking

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Jaybird180    30

Push a motorcycle's front tire up to a wall. Start the engine, put it in gear and release the clutch. Notice which way the subframe moves. Get on the gas a bit then slam the throttle shut, notice what happens.

Try it a couple times if you miss it.

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Lnewqban    11
14 hours ago, Jaybird180 said:

Push a motorcycle's front tire up to a wall. Start the engine, put it in gear and release the clutch. Notice which way the subframe moves. Get on the gas a bit then slam the throttle shut, notice what happens.

If the engine does not stall, its torque tries to move the machine along the only degree of freedom that it has in that situation: vertically up.

As both suspensions gives some, the frame goes high a little under torque and it goes down back to original repose height when the torque ceases.

I like discussing this with you, Jay, as well as posting in a simple manner about things that are complicated, with the hope that it will help other riders that will read this thread in the future.

Do you agree or disagree with the ideas of our previous posts?

Doesn't the concept of some time needed for the transfer of weight to be complete for full braking capability work for your original post?

bikeforces.PNG

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Jaybird180    30

We are in agreement from opposite ends of the spectrum. I think the only thing we need conference on is the purpose for the time.

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fossilfuel    5

All of my experience over the last ten years has been on the track. I can tell you that braking smoothly whether forcefully or not is very important. Analyzing the physics of the action can be fun but the act of braking doesn't need to be over complicated. Coming in hot and abruptly releasing the throttle to stab the brakes can produce negative inputs. I have a perfect example: I was racing at Sonoma trying to get a podium position getting as much drive between turn 6 and the very beginning of the carousel. I came over the top to the entry on the brakes so hard that I had the rear wheel up off the ground a good foot. I made a mistake stabbing the brakes. This action totally screwed my entry and line. I have become quite good at braking late so this was a little embarrassing. The way I like to do it, which might be different for others, is to release the throttle from my grip allowing the throttle to spring back shut. I use a two finger touch on the brake lever so I relieve pressure on the throttle, pulling in on the brake lever as I reapply pressure on the bar.

I had much rather have a smooth, concise, controlled rhythm to corner entry than chaos. We can achieve the white knuckle pressure to the front brakes but in a way that helps the rider and the mechanics of the suspension stay in control, apply the g force to the body smoothly, controllably so that my inputs do not negatively effect entry and corner speed. Once we get a little out of control on braking at corner entry we lose sight of what we need to do at mid corner and corner exit. The eyes should be up, the head turned and looking through the exit once we know we have successfully entered the corner. This is hard to do when we are not completely in control. 

A little less theoretical and little more pit talk. Sorry if I'm a little off intended topic but reading this thread brought this to mind. Cheers!

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PGI    4
On May 21, 2017 at 6:43 PM, Lnewqban said:

This is the way I understand throttle control rule number two in Chapter 6:

Fine modulation of the throttle helps you read the forces that you feel more accurately.

The advantage of that is that your entry speed will be more consistent and appropriate than if you grossly decelerate in a hurry (charging the curve), just to find out that your entry speed (at the end of that precipitate deceleration) is lower than it should be (because your senses were overwhelmed, you are erring on the safe side of entry speed).

The error about the entry speed is more significant for any fast-entry turn, especially due to the aerodynamic drag explained by Hotfoot above.

Good point about senses overwhelmed, or losing sense of speed.

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jcw    6

This talk about speed of weight transfer on the front brakes has some real world relevance.

If you look at the anti dive front suspensions from recent past, even BMW's duolever front suspension, when you take away fork dive blunting the abrupt weight transfer, the sudden loading of the front wheel can overwhelm traction.

 

I've never ridden a bike with anti dive forks. I only have read about this limitation.

 

Any first hand experiences?

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