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Old 11-12-2012, 01:30 AM   #271
Andrew011
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Originally Posted by Wraith Rider View Post
Given that all three of them aim for the same cornering speed, in my opinion the accelerating rider is safest, because up to the apex he is always slower than the other two. Thus he has more time to react, a shorter braking distance and more reserves.
I can not completely agree with this. Cornering speed is not the common goal for all 3 riders (we are not trying to level them in a racing like situation). Also, there are more factors that determine the stopping time and distance than the speed at the moment when braking is initiated. If trying to stop from being on the gas moment before that, a rider first needs to put the fingers on the brake lever (this costs a little bit of time and distance), then needs to gradually apply the brakes before the hard braking starts in order not to stab the brakes (costs more time and distance). When trail braking, a rider already covered both of these actions and needs less time and distance to react in my opinion.

There is a great lesson about braking from Ty Howard - http://www.youtube.com/watch?v=QEhvLELEvRI
On 3:45 and 5:50 he explained the importance of trail braking in a situation we were talking about, from the safety aspect.

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Being afraid to brake while leaning is something completely different from not to habitually trailbrake. That's not even apples and oranges what you are trying to compare. In addition, according to your description your friend aimed for a higher cornering speed, otherwise you wouldn't have had the same entry speed.
I didn't compare anything, I tried to explain why he ran wide. He misjudged the decreasing radius corner (we were never on that road before), and when it closed more and more, he didn't use brakes while leaning, straightened the bike and got himself in the bushes beside the road, he didn't crash, just stopped there. I kept my fingers lightly on the brakes and tightened the corner as needed. This is the experience that convinced me about how trail braking can be useful in situations like these.
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Old 11-12-2012, 02:07 AM   #272
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Originally Posted by Andrew011 View Post
Cornering speed is not the common goal for all 3 riders (we are not trying to level them in a racing like situation). Also, there are more factors that determine the stopping time and distance than the speed at the moment when braking is initiated.
Well, to compare we HAVE TO make some things common goals for all our test subjects, BECAUSE there are so many factors that have an impact on stopping distance. Same apex speed for all three is a necessity.
Yes, it needs some time to overcome lever way and build braking pressure, but it's very hard to evaluate if that outweighs the higher speed.
After all, when I come in fast and sight distance is critical I cover my brakes to reduce reaction time but don't necessarily brake. (Linked front and back brakes are by the way very nice for that because I don't have to use my fingers.)

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Originally Posted by Andrew011 View Post
I didn't compare anything, I tried to explain why he ran wide. He misjudged the decreasing radius corner (we were never on that road before), and when it closed more and more, he didn't use brakes while leaning, straightened the bike and got himself in the bushes beside the road, he didn't crash, just stopped there. I kept my fingers lightly on the brakes and tightened the corner as needed. This is the experience that convinced me about how trail braking can be useful in situations like these.
In that situation it was useful to brake. I just don't think that it helps to brake in every corner instead of only in that special situation. Of course one should be comfortable with braking leaned over, no argument here.
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Old 11-12-2012, 03:01 PM   #273
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Originally Posted by Andrew011 View Post



I didn't compare anything, I tried to explain why he ran wide. He misjudged the decreasing radius corner (we were never on that road before), and when it closed more and more, he didn't use brakes while leaning, straightened the bike and got himself in the bushes beside the road, he didn't crash, just stopped there. I kept my fingers lightly on the brakes and tightened the corner as needed. This is the experience that convinced me about how trail braking can be useful in situations like these.
'
Yup, that's my modus operandi too. Turns an "oh shit" corner into a "weeeeeee" corner.
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Old 11-12-2012, 07:52 PM   #274
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Originally Posted by Jim Moore View Post
Nah, the relatively primitive stuff they use in motorcycle magazine tests can show throttle position. I'm sure the telemetry is legit. I kinda wonder if the timing is perfect.

They use the rear brake pedal to keep the front wheel down as they accelerate..

They use the rear brake pedal for allot of reasons, I'm just saying I've never seen it show up on the telemetry though...
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Old 11-13-2012, 02:22 PM   #275
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Originally Posted by B.Curvin View Post
Some of the really fast SM guys don't use the rear brake at all. The rear is unweighted to the point that just letting the clutch out gets the rear sliding. With a slipper clutch it's even easier.
Thanks for the replies!

I distinctly remember my ZX-7's rear jumping around under hard braking going into some of the turns at Nelson Ledges (the only track I've ever done track days on - it was closest to home), so not only was it definitely unweighted, but I probably shouldn't have been even trying to use the rear brake or deceleration at all at those points where my rear was bouncing up. I was getting comments during the breaks from different people who were behind me at the time, they were taken back by how much my rear end was jumping around upon entry to one of the corners (always from non-racer track-day riders I was faster than through those corners, so I'm guessing they just weren't entering with as much speed, or not braking as hard or late? How often to the actual smooth and fast experienced guys lift the rear up when braking before entering turns?). Admittedly, it wasn't the smoothest thing to be doing, but I wasn't sure how to use an unweighted rear in the turn, nor what would make the skipping-rear lessen without intentionally slowing my entry speed sooner.
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Old 11-13-2012, 02:23 PM   #276
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Have been following this thread for some time now, but it seems to be going round in circles with no real resolution (bit like forums in general). :)


Trail braking is really all about how hard you can push the tyre grip before it gives up the ghost and looses traction. Perhaps the best way of understanding what is meant by this is by using something called the G-G Diagram which is often used by racing teams to analyse trail braking performance.

It's quite common amongst car racing teams, but there is not so much known about GG analysis in motorcycle racing even though the concepts are broadly similar. Perhaps the best description of GG diagrams and how to use them can be found here http://www.temporal.com.au/ggdiag.htm


With the advent of modern data loggers, it is quite easy to gather GG plot data and in fact my Racelogic Video VBox www.racelogic.co.uk is a very good system that I simply tuck under my seat.


As an example the following video of a Moto Gymkhana course attack, recorded by the Video VBox will help. Although the rider here is not ragging the bike really hard, you will see that the little dot in the middle of the speedo overlay is moving in response to the G forces and it is these forces that make up the raw data for the GG diagram.

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Old 11-13-2012, 02:26 PM   #277
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Originally Posted by Mambo Dave View Post
Thanks for the replies!

I distinctly remember my ZX-7's rear jumping around under hard braking going into some of the turns at Nelson Ledges (the only track I've ever done track days on - it was closest to home), so not only was it definitely unweighted, but I probably shouldn't have been even trying to use the rear brake or deceleration at all at those points where my rear was bouncing up. I was getting comments during the breaks from different people who were behind me at the time, they were taken back by how much my rear end was jumping around upon entry to one of the corners (always from non-racer track-day riders I was faster than through those corners, so I'm guessing they just weren't entering with as much speed, or not braking as hard or late? How often to the actual smooth and fast experienced guys lift the rear up when braking before entering turns?). Admittedly, it wasn't the smoothest thing to be doing, but I wasn't sure how to use an unweighted rear in the turn, nor what would make the skipping-rear lessen without intentionally slowing my entry speed sooner.


If it's "hopping" as in bouncing on and off the ground pull the clutch in some to get rid of the chatter.
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Old 11-13-2012, 02:32 PM   #278
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Originally Posted by crofrog View Post
If it's "hopping" as in bouncing on and off the ground pull the clutch in some to get rid of the chatter.
Thanks. Wish I would have asked that question back when I was doing track days instead of now.

It just isn't a concern on the street.
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Old 11-13-2012, 02:49 PM   #279
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Thanks. Wish I would have asked that question back when I was doing track days instead of now.

It just isn't a concern on the street.
Yeah - watch pulling that clutch in when the back end is stepped out. Will be a fantastic high side if you do. Slippers rock.

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Old 11-13-2012, 02:55 PM   #280
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Yeah - watch pulling that clutch in when the back end is stepped out. Will be a fantastic high side if you do. Slippers rock.

Barry
Ah good point. Once it's started hopping it can be hard to get it to stop. More rear brake and pull the clutch in more to get it slide smoothly and I do wish I had a slipper in my SMR...
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Old 11-13-2012, 03:05 PM   #281
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Ah good point. Once it's started hopping it can be hard to get it to stop. More rear brake and pull the clutch in more to get it slide smoothly and I do wish I had a slipper in my SMR...


Yeah... the rear brake quiets it some (on my wife's TTR125 indoors). The 560 SMR I learned to ride without the slipper. Then I got a slipper in there and it was all sunshine and roses. HUGE difference in riding the bike hard.

I can tell you if the bike gets squirrely, DO NOT pull the clutch in, just ride it out.

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Old 11-14-2012, 03:32 AM   #282
Motogymkhanaman
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Had a good dig around and came up with a very interesting scientific paper that answers the trail braking question.

It's a bit technical but at leat the conclusions are in plain English.

http://dinamotoweb.dimeg.unipd.it/di...%20Beijing.pdf
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Old 11-14-2012, 06:33 AM   #283
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Originally Posted by Motogymkhanaman View Post
Had a good dig around and came up with a very interesting scientific paper that answers the trail braking question.

It's a bit technical but at leat the conclusions are in plain English.

http://dinamotoweb.dimeg.unipd.it/di...%20Beijing.pdf
That's a pretty good article and that 125 trace in the picture was what I was talking about earlier about not returning to center.

I knew you could brake hard while leaned over a bit, now I know why.

It also explains to an extent why sm riders back it in. It's going to be less likely to do a stoppie which means more grip can be used for stopping.
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Old 11-15-2012, 03:10 AM   #284
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Originally Posted by crofrog View Post
That's a pretty good article and that 125 trace in the picture was what I was talking about earlier about not returning to center.

I knew you could brake hard while leaned over a bit, now I know why.

It also explains to an extent why sm riders back it in. It's going to be less likely to do a stoppie which means more grip can be used for stopping.
I've pulled the rear wheel off the ground with maybe a 20* learn. Its really quite amazing how good new tire technology is. I didn't do that with warmed slicks, that was performance street tires, not even DOTs.
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Old 11-15-2012, 03:16 AM   #285
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I've pulled the rear wheel off the ground with maybe a 20* learn. Its really quite amazing how good new tire technology is. I didn't do that with warmed slicks, that was performance street tires, not even DOTs.
Yup, It's only recently I have actually started pushing my rubber, wet & dry and yeah, they stick like araldite if you ride well.
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