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More Throttle?


Roddy
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I'm having a bit of an issue with my medium to fast speed sweepers. I'm finding that I'm having to pull on my inside bar to stop the bike leaning in further once I get on my chosen line. I know the obvious answer is to load up the rear and roll on faster than what I'm already doing, but it feels like if I do that, I'll either start running wide off my line or start getting to the edge of rear grip since I'm already over 45 degree lean. I'm locked in enough to be able to release all pressure on the bars. That's what I'd like to do, but it feels like I'd need lots of throttle to get the bike to track the line with no handle bar pressure. Is it just a matter of throttle control?

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This is a problem that I have had as well. You get the turn in but once the cornering forces aren't there the bike wants to climb up the inside curbing. Then you find yourself adjusting your steering input and breaking the steering rules.

 

Ultimately this all comes down to confidence. From your description it sounds like you recognize the solution to the problem.

 

Lets take a moment to look at the "What if's"

 

1. What if you go wide? Can you use the hook turn technique to prevent that?

 

2. What if you loose rear grip? Is that an instant crash situation or are there things you can do (or more specifically not do) once the rear starts sliding?

 

3. Are there people on similar bikes going through that section faster? How do you think they are accomplishing this?

 

In my particular case I tracked my lack of confidence to my visual skills and I'm working on those. I did not have enough reference points and felt somewhat "lost" in the longer higher speed corners. How many reference points do you have in the corners that are giving you problems?

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Is your bike neutral steering in other corners ?

 

I believe the tendency for the bike to continue to turn in can be caused by a number of things from tire profile and inflation to geometry issues.

 

Have you modified the bike's geometry in any way ? Had the suspension set up ?

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What, specifically, are you looking at as you go through one of the corners where you experience this? Are your eyes tracking the inside edge of the track?

 

Have you ever tried riding a circle in a parking lot and using the throttle alone to change the radius of your circle, just to experiment with it?

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I'm having a bit of an issue with my medium to fast speed sweepers. I'm finding that I'm having to pull on my inside bar to stop the bike leaning in further once I get on my chosen line.

 

Some bikes are under-steering, some are neutral-steering (ideal) and some, like yours, are over-steering.

The reason for that to happens has to do with the balance (or lack of) of the lateral deformation of both contact patches under cornering forces (camber thrust and slip angle).

 

Things can get better or worse by modifying the pressure of each tire first; then, by replacing the brand/profile of the tires.

In severe cases, changes in the geometry of the steering (higher or lower front/rear suspension-chassis) must complete the above mentioned.

 

Riding faster only increases the angle at which the bike must lean and the deformation of the patches.

Same for strong acceleration, with the undesired bonus of standing the bike some and tending to run wide, unless you keep pressing forward on the inside grip.

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Yeah. I think throttle control may be an issue but I'm not actually having to change my angle of lean after the initial steering input. The bike doesn't really want to run a tighter line because of a lack or mid corner speed.

 

Hotfoot, yeah you're right. I'm focusing on the inside kerb. One of the corners I'm experiencing this is a double apex and I'm using the distance from the kerb as a reference between the 2 apexes. I do stop my roll on there momentarily but even after I start rolling on again, I'm still having to pull the inside bar. I am applying the throttle control rule as I understand, but maybe not enough?

 

Yep. There are other riders that roll on faster towards the second apex. I'm working up to it slowly.

 

The other place is a long high speed sweeper where I'm rolling on going into and through it and I'm also using the kerb as a reference until it opens up and I can see the exit. Still have to keep some pressure on the bar there.

 

I understand what happens when you get greedy with throttle roll on. The bike runs wide and you have to roll off and re point the bike for the exit or drop your upper body for the hook turn.

 

I guess the age old question is how much roll on is the right amount. It just feels like it would need a lot more gas to make it neutral. Going a little wide isn't a problem but losing rear traction at steep angles of lean and over 1G cornering force is something I definitely would rather avoid.

 

The bike is perfectly neutral at lesser angles of lean on the street but I can also be more aggressive with my roll on at those angles.

 

It's a bog standard 2006 GSXR 1000 and 29psi front and rear.

 

Thanks all for your insights. Love this forum.

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"I understand what happens when you get greedy with throttle roll on. The bike runs wide and you have to roll off and re point the bike for the exit or drop your upper body for the hook turn."

 

Which one of these would allow you to stay on the gas and not risk making the bike less stable? Which one of these works best with the throttle control rules?

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"Have you ever tried riding a circle in a parking lot and using the throttle alone to change the radius of your circle, just to experiment with it?"

 

Hotfoot. That's a great idea. I'm going to have to try this one myself!

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If you are looking at the inside edge of the track, it is REALLY EASY to unconsciously steer the bike to the inside, which would make you have to pull on the inside bar to correct. You could try changing your reference points so you are looking more to the outside and see if the bike stops falling inside.

 

Are your problem turns left handers? Could you be pulling slightly on the right bar when you are rolling on the gas?

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Hotfoot, yeah you go where you look but I'm not really correcting my line. I wouldn't call it a a steering input. I'm having to provide constant pressure (pull on the inside bar - so in effect trying to stand the bike up, not counter steer into the kerb) when I'm tracking my line through long corners and even when rolling on. Left and right turns are the same. It's not lots of pressure....just a little. If I let go, then the bike feels like it'll basically ride off it's wheels.

Lnewqban. I have ridden bikes that need a constant push on the inside bar to stay in a lean and only become neutral with an aggressive hang of position, even at low lean angles and speeds. As I understand it....and I don't really understand it a lot. It has lots to do with the geometry...specifically trail.

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Hotfoot, yeah you go where you look but I'm not really correcting my line. I wouldn't call it a a steering input. I'm having to provide constant pressure (pull on the inside bar - so in effect trying to stand the bike up, not counter steer into the kerb) when I'm tracking my line through long corners and even when rolling on. Left and right turns are the same. It's not lots of pressure....just a little. If I let go, then the bike feels like it'll basically ride off it's wheels.

Lnewqban. I have ridden bikes that need a constant push on the inside bar to stay in a lean and only become neutral with an aggressive hang of position, even at low lean angles and speeds. As I understand it....and I don't really understand it a lot. It has lots to do with the geometry...specifically trail.

 

Roddy, I don't want to overstress this point, because it may indeed be a tires or geometry issue, but let me just say this - it is REALLY REALLY common for riders to have a very slight pressure on one bar and NOT have ANY IDEA that they are doing it, and it has the EXACT effect you are describing - the bike either inexplicably runs wide or 'falls in' to the inside. The rider is COMPLETELY sure they are loose on the bars. BUT, when they change where they look, the problem disappears and THAT is when there is recognition that there was some slight, unconscious pressure on the bars. It is a simple thing to test, just try changing your reference points so that you are not focusing on the inside of the track. A great test would be to ride 2 laps looking to the OUTSIDE (ride at a moderate pace since you are changing things around) then try 2 laps looking to your old reference points, then maybe try two laps looking more mid-track, and just check to see if anything changes in the bike's handling. I don't want to force this on you but it DOES sound a lot like a vision problem and that is a much easier thing to test than playing around with geometry or tires! (BTW another thing that causes the bike to steer too tightly to the inside is "looking through the corner". If a rider's sight line is TOO far ahead in a corner, and crosses over the curb or dirt of the inside of the track, that sight line will cause the rider to unintentionally ride the bike too far to the inside - another thing to look out for.)

 

The next thing I'd check are your front suspension settings - if your compression damping setting is really low (soft) and rebound damping is really high, you could be compressing your forks on turn entry but maybe they aren't rebounding quickly enough on turn exit. Good throttle control extends the forks back into the mid-range, but if the rebound damping is way too high, they may not be able to extend quickly enough as you roll on.

 

Regarding throttle control, do you have any electronics that can measure your speed or acceleration? If the bike is still slowing down at the point that it feels like it falling into the inside, that is a clear indicator that you are not giving it enough throttle to keep it on a consistent line - fi you are still slowing down, your arc will naturally tighten. Have you tried entering the corner at a lower speed, so you can give it more throttle without worrying about losing the rear? Did the bike stay on your chosen line when you did that? Do you think that as you are riding the trouble corners now, that your are giving it enough throttle to achieve the ideal 40/60 weight distribution recommended in Twist of the Wrist II?

 

 

FYI, I am not saying there couldn't be a problem with the bike's setup, because there could be. But checking the basics of rider control is easy and doesn't cost anything except track time; chasing a setup problem that turns out to be a rider problem can cost a fortune. You asked a really smart question, in your original post, it's a wise move looking at technique first. :)

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"Have you ever tried riding a circle in a parking lot and using the throttle alone to change the radius of your circle, just to experiment with it?"

 

Hotfoot. That's a great idea. I'm going to have to try this one myself!

Hotfoot- I'm wondering if you could jump on the steering bike and try this and let us know if throttle alone can change turning radius. I think it would bust a lot of myths related to steering and set us all straight.

 

Question: Didn't someone use a Radio Controlled toy motorcycle to demonstrate this once? Or did we just "toy" with the idea. I can't really be sure.

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"Have you ever tried riding a circle in a parking lot and using the throttle alone to change the radius of your circle, just to experiment with it?"

 

Hotfoot. That's a great idea. I'm going to have to try this one myself!

Hotfoot- I'm wondering if you could jump on the steering bike and try this and let us know if throttle alone can change turning radius. I think it would bust a lot of myths related to steering and set us all straight.

 

Question: Didn't someone use a Radio Controlled toy motorcycle to demonstrate this once? Or did we just "toy" with the idea. I can't really be sure.

 

 

Just to make sure there is no confusion on this: I am not saying that the throttle will "stand the bike up" and steer it out. That is NOT the case. I am talking about using the throttle to increase your SPEED. If you are riding a circle and speed up while keeping the exact same lean angle (no steering inputs) the radius of your circle will increase. I won't go into the physics formulas because there are a lot of threads on the forum that already talk about it, but the short version is: if you know the speed and lean angle, you can calculate the radius of the arc the motorcycle will take. In practical terms, you can experiment with this in a turn - if you let off the throttle gradually (not abruptly) and allow the bike to slow down, the arc will naturally tighten as the bike slows; if you give the bike enough throttle to INCREASE your speed the arc will widen, all of this WITHOUT changing your lean angle.

 

Reminder: it takes a certain amount of throttle just to overcome the forces of turning. If you are "flat" on the throttle (holding it steady instead of rolling it on) in a corner, you are slowing down. It can be surprising how much of a roll-on it takes (especially in a high speed sweeper) to actually INCREASE speed.

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Hotfoot. I really appreciate you going to the effort of posting all of that and giving me some things to work on, and of course Ill take all your comments on board and try them next time Im out on track. The best upgrade is always the squishy bit in the middle.

 

Bouncing on the front end has the forks extending back up in under a second. I would think that its in the ballpark.

 

I have a GPS receiver working with Racechrono on my phone and I have a camera on the tank which records my speedo, so I can see that Im increasing speed after turning (except for the double apex where the speed drops a little before I start my roll on again). Thats a good point about fast sweeping turns and throttle roll on. I find even rolling on into a the fast sweeper, the speedo still drops slightly before rising. The speed drop is actually more pronounced than indicated on the speedometer due to the smaller radius of the tyre at the edges.

 

Unfortunately I wont be able to get out again till March. Im eager to incorporate your suggestions and experimenting with reference points and were Im looking, as well as getting onto that throttle nice and early.

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chasing a setup problem that turns out to be a rider problem can cost a fortune.

 

 

This ^^^^

 

Been there, done that. And as the rider I was SURE I wasn't doing the thing that I was, in fact, doing (applying rear brake under heavy braking at the end of the straight, causing violent rear wheel hop...misdiagnosed by the numb skull rider as a front suspension issue).

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Hotfoot. I really appreciate you going to the effort of posting all of that and giving me some things to work on, and of course Ill take all your comments on board and try them next time Im out on track. The best upgrade is always the squishy bit in the middle.

 

Bouncing on the front end has the forks extending back up in under a second. I would think that its in the ballpark.

 

I have a GPS receiver working with Racechrono on my phone and I have a camera on the tank which records my speedo, so I can see that Im increasing speed after turning (except for the double apex where the speed drops a little before I start my roll on again). Thats a good point about fast sweeping turns and throttle roll on. I find even rolling on into a the fast sweeper, the speedo still drops slightly before rising. The speed drop is actually more pronounced than indicated on the speedometer due to the smaller radius of the tyre at the edges.

 

Unfortunately I wont be able to get out again till March. Im eager to incorporate your suggestions and experimenting with reference points and were Im looking, as well as getting onto that throttle nice and early.

 

Sounds great, let us know how it goes!

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Just to make sure there is no confusion on this: I am not saying that the throttle will "stand the bike up" and steer it out. That is NOT the case. I am talking about using the throttle to increase your SPEED. If you are riding a circle and speed up while keeping the exact same lean angle (no steering inputs) the radius of your circle will increase. I won't go into the physics formulas because there are a lot of threads on the forum that already talk about it, but the short version is: if you know the speed and lean angle, you can calculate the radius of the arc the motorcycle will take. In practical terms, you can experiment with this in a turn - if you let off the throttle gradually (not abruptly) and allow the bike to slow down, the arc will naturally tighten as the bike slows; if you give the bike enough throttle to INCREASE your speed the arc will widen, all of this WITHOUT changing your lean angle.

 

Reminder: it takes a certain amount of throttle just to overcome the forces of turning. If you are "flat" on the throttle (holding it steady instead of rolling it on) in a corner, you are slowing down. It can be surprising how much of a roll-on it takes (especially in a high speed sweeper) to actually INCREASE speed.

 

My impression is that the radius of a turn tightens (decreases) when I roll on the throttle, of course the increased speed in the end widens the turn, but when rolling on the rear wheel creates a force outside (by pushing forward), because in the radius of the turn the rear wheel is outside, the front wheel is more inside ... not talking about sliding here, just a normal rollon ... or am I totally wrong here ?

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Nope. That's pretty much it. Motorcycle tires "slip" all the time. It's subtle but once the forces start to act on the bike it naturally gets pulled away from the apex. We can counteract this by shifting our weight to the inside of the corner but only up to a point. Even the pro's don't get unlimited corner speed by hanging off.

 

What's really interesting is if you have one of the bikes out there with a data logging system you can actually go in and see this "slip" on the data. The bikes measure the slip and use that to react with their traction control systems along with other sensors such as lean angle or yaw sensors. Slip data is calculated by the differences in speed between the front wheel and rear wheel. The front wheel just rolls while the rear wheel has the forces from the engine pushing the bike forward.

 

The act of twisting the throttle causes an increase in engine RPM which results in an increase in speed. This speed increase causes an increase in slip and the increased cornering forces plus slip cause the bike to widen it's arc.

 

Predicting slip and it's affect on the bike's arc at different speeds is quite honestly some confusing stuff. Add in the way our body position directly translates to less lean angle and how the weight of the bike also helps change the slip and you can wonder what the heck is going on.

 

That's actually exactly what happened to me. I got used to the "going wide" and adjusted my speed accordingly so I held my line. Then I improved my body position that changed the equation and allowed me to increase my speed. At first of course the same steering input that turned the bike nicely aimed me straight at the apex. I adjusted of course. After that I got another bike with some superlight wheels on it and that unbalanced my mental slip and steering equation all over again.

 

When we are used to the bike reacting one way and it reacts differently that can seriously affect our confidence. It can work in both directions. Going in slower and seeing the apex and inside grass coming at you or going in too fast and seeing the edge of the track and the gravel trap waiting to catch you.

 

What's amazing to me is riders like the coaches at the Superbike School who can change their technique on the fly and know exactly what to expect. When they are following the slow students they often don't hang off because it's not needed and know the exact steering input to put in. When they are going faster they automatically adjust again. If you think about how a coach might have a really slow student plus a really fast student in the same session this is some pretty amazing adaptation. :)

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Thank you rchase, I was already doubting my mind about this :) ... I'm always early on the gas and it's kinda funny sometimes to see someone in the rearview following you into a corner needing much more leanangle, (even scratching footpegs sometimes!) just because he waits for the apex with the rollon...

 

so it's not the Fireblade, it's Keith Code's techniques that make the difference LOL

 

Uli

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Been there myself with the self doubt of my grasp of the concepts. I added in the self doubt of my own abilities for good measure too. I find for me that understanding the physics of whats going on better helps me stay calmer when on on the wrong side of the slip rate and the bike is going wide or eating apexes. Knowing for an absolute fact that adding more power is going to help lets the logical part of my mind override the primitive part of my brain that's trying to fire off SR's like crazy.

 

While it feels safer slower it's actually safer a bit faster. Keeping tires hotter and cleaner gives you more grip.

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Nope. That's pretty much it. Motorcycle tires "slip" all the time. It's subtle but once the forces start to act on the bike it naturally gets pulled away from the apex.

 

The act of twisting the throttle causes an increase in engine RPM which results in an increase in speed. This speed increase causes an increase in slip and the increased cornering forces plus slip cause the bike to widen it's arc.

 

 

 

I could be missing something, but this doesn't make sense to me. Adding throttle causes the bike to widen its arc but I don't think tire slip comes into this, unless you are drifting both tires (!). I think it is just the increase in speed increasing the centripetal force (lateral acceleration) that moves the bike to the outside, or else requires more lean angle or more weight to the inside to maintain the same turn radius.

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Yellowduck. With the grip of modern rubber how do you think the bike is widening it's arc? You are completely spot on on the forces but the tires have to give a little bit in order for the line to change otherwise the bike would stay exactly on the same arc. That little tiny bit of give is slip. It's nothing like a full on drift. This is something I scratched my head about for quite sometime about and is something i would love to understand a LOT more about.

 

"A non-zero slip angle arises because of deformation in the tire carcass and tread. As the tire rotates, the friction between the contact patch and the road results in individual tread 'elements' (finite sections of tread) remaining stationary with respect to the road. If a side-slip velocity u is introduced, the contact patch will be deformed. When a tread element enters the contact patch, the friction between the road and the tire causes the tread element to remain stationary, yet the tire continues to move laterally. Thus the tread element will be ‘deflected’ sideways. While it is equally valid to frame this as the tire/wheel being deflected away from the stationary tread element, convention is for the co-ordinate system to be fixed around the wheel mid-plane.

While the tread element moves through the contact patch it is deflected further from the wheel mid-plane. This deflection gives rise to the slip angle, and to the cornering force. The rate at which the cornering force builds up is described by the relaxation length."

 

A quote from Wikipedia. And the full article here. Its important to note that this article is about car handling and the rounded profile of motorcycle tires and the different wheel configuration do change the physics slightly.

 

Cars understeer or oversteer slightly because of slip but those actions occur way before the tire starts to completely loose grip. That's slip. You probably also feel it when you head into a corner too hot and feel the front end just start to push a little bit but not completely loose it's ability to hold the bike.

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What's really interesting is Scrmnduc who I do the school with every year showed me one of his photos where on corner entry his front tire on his rented school bike was highly deformed. The photographer caught it at exactly the right moment. I'm going to try to get him to post the image if he has a chance and if he's willing. :)

 

If he does not end up being able to post the image here's a consolation visual. Tire deformation on a 4 wheeled vehicle.

 

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