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Quick Steering Confusion


faffi
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Today, riding my old KZ650 at a sedate pace, I still practiced the one steering input and quick steering. Around one bend, doing about 70 kph (40-45 mph) I waited very long before snapping the bike on its side.

 

And became seriously surprised when I touched down! That wasn't expected, as the corner can be taken much faster using a normal, lazy turn just following the road's arch.

 

I then started thinking, and that's when the logic about reduced lean using quick steering began to feel less logic. If I keep the same speed and use for instance 150 metres to change direction, it will demand a certain amount of lean to complete, depending on speed and radius. By changing, I mean from corner entrance to corner exit, bike upright to bike upright again. Now, if I keep the speed constant, but shorten the corner to just 50 metres, will I not have to lean more? Sure felt like it.

 

Under racing conditions, the average speed from corner entrance to corner exit can be kept higher because you can stay upright longer. But would not apex speed be lower then, since you make the corner in reality much shorter?

 

Please enligten me :)

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I believe the theory behind the quicker steering input = less lean angle is based on using the same turn point, moving the turn point in your corner drastically like you suggest means your taking a entirely different line through the corner and comparing the lean angle used between vastly differing lines is like comparing apples to oranges, or perhaps 125's to 1000's

 

If your trying to achieve the same amount of turning in 50 meters that you normally do in 150 I would say you will most definitely need a heck of a lot more lean angle, but again I think that's beside the point of the quick steering/reduced lean technique, consider your initial 150 meter turn, if you turn in slowly and take the first 50 meters to reach your lean angle you have 100 meters left to complete the turn and require enough lean angle to do so, now consider turning in quickly in say 15 meters, you now have 135 meters available to complete the turn and require less lean angle to make the same corner.

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Imagine two straight lines connected by a curve of constant radius.

Both points of transition represent two perfect quick flicks.

 

Any lazier entering and leaving flicks than the previous ones will deform the transition points and the curve, decreasing the minimum radius (compared to the previous one).

That reduced radius will force a bigger lean angle (or its alternative: a slower curve speed).

 

The trick of a big steering input while the bike falls into and comes back from the max lean angle is that many degrees of turning are achieved in the process.

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The other thing to keep in mind is that if you want to shorten the corner by that much, and keep the same speed (or increase your speed at the same turn point), you will have to improve your quick flick even more - otherwise it just won't be possible. So quick flick is not the problem, but rather it's the only solution. wink.gif

 

 

Quick turning is part of the solution to make a corner shorter (in combination with a late turn point) and spend less time on the edge of the tyre. Less time is used to reach the required lean angle, but also the total lean angle required will be less (compared to an earlier turn point using lazy steering).

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QS only promises reduced lean OUT of the turn imho.

QT should also reduce the maximum lean required for the same speed, turn point and apex.

 

We had a longish discussion some time back when Eirik (I think?) asked about the effects of the QT.

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Yes, I've brought it up before, but I must say I got confused when the QT made me touch down in a corner that ridden lazely will leave acres of clearance. Had I, OTOH, used quick-turning at the normal steering point and made the corner as long as usual, I could have completed the corner with less lean than a lazy turn-in. At least that's how I undestand it now, slow as I am.

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I would say a quicker turn in can have a number of possible effects on your turn depending on what else to change to match the increased rate of turn in. For example if your speed and lean angle are constant your turn will be shorter, if your turn length and lean angle are constant you can carry higher speed, and if your speed and turn length are constant you can use less lean, but unless your going from a dangerously slow rate of turn in to a world champion rate of turn in I don't think it will have a large enough effect to significantly improve more then one aspect of the corner, IE. both a increase in speed and reduced lean

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Had I, OTOH, used quick-turning at the normal steering point and made the corner as long as usual, I could have completed the corner with less lean than a lazy turn-in.

 

 

That's what quick turns are for! You have to move your turn-in point a bit to make it work but yes, less lean angle for the same bend (so possibly more speed as the next change) is what you're trying for.

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