# Isolating Line Issues

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Watching a video the other day by Max McAllister as I wanted to learn something about motorcycle geometry (still seeking) and he was talking about swingarm geometry and how a change in sprocket ratio alters it, causing problems with being able to finish a turn.

My takeaway from the video lecture is that turn-in to apex issues the technician needs to look at the front end of the motorcycle and from apex to exit, the rear of the motorcycle.

I'm thinking: How do you know if it's a bike issue or a rider error issue? For example, in Twist II Keith talks about the timing of when you get on the gas and how hard and how that judgment affects the trajectory of the bike. Sounds simple enough. And if there's a discernible pattern to inconsistency then we can say with a high degree of certainty that it's a rider error.

I'm hoping that some of the coaches will chime in. If a student brings their own bike to the school and you see some major line errors, at what point do you know that a bike adjustment is necessary versus the nut on the seat?

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Frist question: does it do it every lap, every turn? If the problem only happens sometimes, it is almost certainly a rider issue.

Typically at a school the coach would follow the student very closely, so that their rate of acceleration throughout the corner (both slowing at the beginning and accelerating later in the turn) matches, and observe, watching the rider and the bike and the line the bike follows. If there is a noticeable difference in line or acceleration rates, the coach would be looking for rider errors and many of them are visible either in the rider's position, or in the way their bike is reacting.

What errors can YOU think of that a coach might be able to see, either by observing the rider or by observing the bike's line or acceleration rate? Let's say you are closely following another rider and you see that they are wide at the apex by a few feet and end up wide on the exit. The corner is a little bumpy so you can see the how the rider is affected by that. The rider is sitting reasonably upright. You also notice that right after the turn point the rider pulls suddenly away from you a little bit, but later in the corner (near the exit) you run up on them a bit and have to back off the throttle.

There are a whole variety of errors that could be occurring, which ones can you think of?

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Thinking....but feel free to toss a underhand slow-pitch hint my way. It's late in the day.

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Thinking....but feel free to toss a underhand slow-pitch hint my way. It's late in the day.

How would the rider look different over the bump if he/she was relaxed and going with the bike versus tense, braced, or fighting it?

What effect would tense or braced arms have on the line the bike holds, and why?

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Thinking....but feel free to toss a underhand slow-pitch hint my way. It's late in the day.

What effect would tense or braced arms have on the line the bike holds, and why?

This is a very good question, anyone want to take a swing at answering it?

In other words, if you were a coach following a student, what would you expect to see with a rider that had tense or braced arms on his/her line? What's the bike going to do?

CF

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^^^ bike is going to go upright and straight not leaning into the turn.

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Frist question: does it do it every lap, every turn? If the problem only happens sometimes, it is almost certainly a rider issue.

Typically at a school the coach would follow the student very closely, so that their rate of acceleration throughout the corner (both slowing at the beginning and accelerating later in the turn) matches, and observe, watching the rider and the bike and the line the bike follows. If there is a noticeable difference in line or acceleration rates, the coach would be looking for rider errors and many of them are visible either in the rider's position, or in the way their bike is reacting.

What errors can YOU think of that a coach might be able to see, either by observing the rider or by observing the bike's line or acceleration rate? Let's say you are closely following another rider and you see that they are wide at the apex by a few feet and end up wide on the exit. The corner is a little bumpy so you can see the how the rider is affected by that. The rider is sitting reasonably upright. You also notice that right after the turn point the rider pulls suddenly away from you a little bit, but later in the corner (near the exit) you run up on them a bit and have to back off the throttle.

There are a whole variety of errors that could be occurring, which ones can you think of?

I'll take a stab now that I'm just sitting on the sofa after leftover turkey.

If the rider is wide at the apex and wide on the exit while upright, I'd think that they probably are keeping pressure on the handlebars. Probably would be worthwhile to see if the rider is getting a good lock on the tank with the lower body, as the bad interfacing might be the reason for the residual pressure on the handlebar. Possibly might be too close to the tank, causing their knees to be open away from the tank, relating back to the lock on.

If they're pulling away right after the turn point and then getting closer on the back side, I would think they're too aggressive on the throttle after turn in. Maybe they feel uncomfortable with gauging corner entry, so they think they were too slow at tip in, and rolled on the gas to try and get back up to speed. With the aggressive roll on and potential bar pressure, the bike then runs wide. They then probably rolled off the gas as they found themselves drifting out wider than the intended line.

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Thinking....but feel free to toss a underhand slow-pitch hint my way. It's late in the day.

What effect would tense or braced arms have on the line the bike holds, and why?

This is a very good question, anyone want to take a swing at answering it?

In other words, if you were a coach following a student, what would you expect to see with a rider that had tense or braced arms on his/her line? What's the bike going to do?

CF

A stiff-arm rider is going to have ineffective steering. The rider will be reluctant to smartly counter steer the bars and their death grip won't allow the bars to turn-in after releasing steering pressure. I think a coach would see this as a timing issue with every response of the bike happening too late. The rider would then subsequently not trust the steering and would either slow down or steer earlier.

Frist question: does it do it every lap, every turn? If the problem only happens sometimes, it is almost certainly a rider issue.

Typically at a school the coach would follow the student very closely, so that their rate of acceleration throughout the corner (both slowing at the beginning and accelerating later in the turn) matches, and observe, watching the rider and the bike and the line the bike follows. If there is a noticeable difference in line or acceleration rates, the coach would be looking for rider errors and many of them are visible either in the rider's position, or in the way their bike is reacting.

What errors can YOU think of that a coach might be able to see, either by observing the rider or by observing the bike's line or acceleration rate? Let's say you are closely following another rider and you see that they are wide at the apex by a few feet and end up wide on the exit. The corner is a little bumpy so you can see the how the rider is affected by that. The rider is sitting reasonably upright. You also notice that right after the turn point the rider pulls suddenly away from you a little bit, but later in the corner (near the exit) you run up on them a bit and have to back off the throttle.

There are a whole variety of errors that could be occurring, which ones can you think of?

Body Position will be visibly askew. The coach will also be able to see (possibly hear) the throttle action not being smooth as evidenced by the changing relative distance.

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Good responses, folks. When riding closely behind a student, there are lots of things the coach can see, I won't attempt to try to list anywhere near all of them (and riders are endlessly creative so sometimes something totally new pops out at you when following someone), but here are a couple of very common ones you can see, that could cause a bike to run wide and could SEEM to the rider like a suspension problem causing the bike to not hold its line:

1) Rider is tense and/or stiff-arming the bars - you can see this in the how the rider's body reacts over bumps (bouncing stiffly versus visibly relaxed and going with the motion) and sometimes in their general position (braced elbow, for example), but you can also see it in how the bike handles. Tension on the bars can affect how the bike reacts under braking, how it turns in, and what happens to the line throughout the whole corner.

2) Throttle control - a rider could be applying the throttle too early - before he/she is finished steering, before the bike is on the desired line, or too MUCH, rolling on too much too soon and driving the bike wide.

There is a lot more detail that could be discussed in each of these areas as to the exact cause, exact effect on the bike, and exact solution, but to get back to your original question: coaches can see a LOT when leading and following a student, so bike handling and setup is something that we would discuss if there were no obvious rider errors occurring and the student was running noticeably wider than the coach on corner exits even when taking the same line and using similar throttle control, AND if both coach and rider are confident that there is no unwanted bar pressure. Fortunately at CSS we have an excellent mechanic (often two) on site and we can take the bike right over to have him take a look at the setup, checking suspension, tires, and forks, etc., and can often address the problem right there on the spot. The mechanics are well versed in suspension setup and can check the setup on any type of bike.

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