Steering, Track Positioning, Twist Ii, P. 76

[PGI]

Can you give an example of point 3, p. 76 of Twist II?

 

The point states that track positioning is useful when: " A slow turn-in, under-braking turn entry when positioning the bike quickly for the turn point could overload the front tire and cause the front wheel to lock".

 

I understand over-braking while turning will cause a loss of traction, or over-braking can lock up the front wheel, but I'm not understanding this statement. The statement gives me visions of beginning a fast turn early and trail braking (slow turn-in) , positioning the bike for a turning point then making a quick turn in a late apex, decreasing radius turn. Not sure.

[rchase]

Hey. Welcome to the forum! First post and already asking great questions.

 

A tire has a finite amount of traction. When a tire is turning the motorcycle it has cornering forces on it and the contact patch shrinks due to the tire profile. Adding the additional forces of braking to the cornering forces on top of a smaller contact patch can make the front tire lose traction in certain situations.

 

Here's an article about trail braking that might be helpful for some further understanding there.

 

http://forums.superbikeschool.com/index.php?showtopic=4034

[rikker]

I really believe that the front wheel locks when there is NO load, ie, wheel in the air and you hit the brakes before it lands on the tarmac.

[rchase]

Technically the wheel does not lock in mid air. It just stops or slows in its rotation and there's a massive speed mismatch when it lands which overwhelms the contact patch. The results of course are still the same. Lots of smoke and excitement.

[csmith12]

Can you give an example of point 3, p. 76 of Twist II?

 

The point states that track positioning is useful when: " A slow turn-in, under-braking turn entry when positioning the bike quickly for the turn point could overload the front tire and cause the front wheel to lock".

 

I understand over-braking while turning will cause a loss of traction, or over-braking can lock up the front wheel, but I'm not understanding this statement. The statement gives me visions of beginning a fast turn early and trail braking (slow turn-in) , positioning the bike for a turning point then making a quick turn in a late apex, decreasing radius turn. Not sure.

 

Many tracks have these types of corners. Some are lovingly called carousels and sometimes tighten slightly toward the exit. So you enter kinda hot and lazy, with a little lean, then at turn in point there is a "major" steering action. You might hear this in the paddock masked as "line" talk/chatter, because a faster or safer line through the corner is preferred.

 

The skill of it is identifying them before they surprise the rider, any ideas?

 

EDIT: Welcome!

[csmith12]

Also, if you have ever ridden a track with cones to force a line change on entry or exit, then they are using "track positioning" to help riders put themselves in safer areas of the track. (or force a hook turn lol)

[csmith12]

Here is another realistic example..

 

Say your on the front straight pinned at a buck 30. You can pass a rider in upcoming braking zone but it will put you on the inside of the turn. Your normal track position turn entry is more toward the outside, so something is going to have to change to make this pass.

 

How would you apply these 5 skills to this situation?

 

1. track position

2. braking (entry speed)

3. turn in point

4. throttle control

5. hook turn

[Lnewqban]

Can you give an example of point 3, p. 76 of Twist II?

 

The point states that track positioning is useful when: " A slow turn-in, under-braking turn entry when positioning the bike quickly for the turn point could overload the front tire and cause the front wheel to lock".

 

I understand over-braking while turning will cause a loss of traction, or over-braking can lock up the front wheel, but I'm not understanding this statement. The statement gives me visions of beginning a fast turn early and trail braking (slow turn-in) , positioning the bike for a turning point then making a quick turn in a late apex, decreasing radius turn. Not sure.

 

[rchase]

That's one sinister corner. Someone put that extra little bend at the end just for laughs.

[Hotfoot]

Can you give an example of point 3, p. 76 of Twist II?

 

The point states that track positioning is useful when: " A slow turn-in, under-braking turn entry when positioning the bike quickly for the turn point could overload the front tire and cause the front wheel to lock".

 

I understand over-braking while turning will cause a loss of traction, or over-braking can lock up the front wheel, but I'm not understanding this statement. The statement gives me visions of beginning a fast turn early and trail braking (slow turn-in) , positioning the bike for a turning point then making a quick turn in a late apex, decreasing radius turn. Not sure.

 

Has this cleared up for you? Your own interpretation is a valid one. These statements about track positioning sometimes helps students clear up some confusion about a single, quick steering action. In class we talk about a single steering input as the goal in most turns, but there are exceptions, and these points are describing those.

 

An example I can think of is a very fast entry turn (after a straightaway, for example) with a late apex. Since it is a fast entry turn but a late apex, the priority is on carrying speed as long as possible down the straight, so you may still be hard on the brakes at the entry of the turn, so a quick-turn could overload the front. Instead you might make a gradual turn at the entry ("bend it in") while you are still slowing down on the brakes. You would be setting the entry speed for your "real" turn point, later in the turn, and that would be your real steering input.

[PGI]

Thanks everyone.

 

Regarding how to use the skills mentioned to make the pass, making the pass using the double apex will require scrubbing off more speed in the slowest part of the turn, midturn, to negotiate the tighter radius as compared to the ideal line (disadvantage). There is a braking advantage using the double apex line, namely brake later and then apply more force to set the entry speed prior to the quick turn. Because my entry speed would have to be slower to negotiate the tighter turn, this could result in my getting passed during the exit since I would have to be starting the drive from a lower speed than if taking the ideal line. Also, if I'm riding a big bike compared to a smaller, more agile machine, even more speed would have to be scrubbed off to negotiate the double apex line's turning point before the drive, maybe too much to make it worthwhile. Get back on the gas as soon as the bike is pointed at the apex (it will be a little later for the double apex line, which is a disadvantage). The hook turn gets applied at the quick-turn turning point using the double-apex line, made just prior to starting the drive out of the turn, but it could also be applied to ideal line.

 

It's best to work both lines and record the section times to see which can be done most efficiently. Then, if the passing opportunity arises, the double-apex may be the way to go, especially if passing a very slow rider. Also, if the decreasing radius turn is one in a series of turns, the drive out of the turn is moot (unable to take advantage of it), and the double-apex line is likely the better choice.

[PGI]

Yes, looks clear to me now. Two steering points instead of one, for example in the case of the 180 degree turn with the decreasing radius. Use track positioning by "easing in" (i.e. turning) before making the "one" steering change.