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Body Position - Help (pics)


avih

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Hi avih,

 

Generally speaking, I/we come here primarily to learn and discuss Keith Code's "teachings". Here on his school's website/forum, that is. Based on your postings, it seems that you are unfamiliar with the Twist of the Wrist book series. You can purchase copies on the website "store" section here. Keith has trained more world champions than anyone. For what its worth, I used his teachings with great success to win many trophies at the national level for a decade before I retired from professional motorcycle roadracing.

 

Good luck,

racer

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Hi avih,

 

With all due respect, your unfounded, unsupported, untested "theories" are just that, and, based on decades of research by myself and many, many, many others, well... pretty much all wrong.

 

Generally speaking, we are here to discuss Keith Code's "teachings", here on his school's website/forum. Based on your postings, it is pretty clear that you are unfamiliar with the Twist of the Wrist book series (or anything else). You can purchase copies on the "store" section of this website. For what its worth, I used them with great success to win many trophies at the national level for a decade before I retired. (Considering the number plate on the bike you were riding, I thought maybe you were interested in racing, too.)

 

In any case, this thread is about body position.

 

Good luck,

racer

 

Racer, as you've managed to forget by now, I have read those books and I do have them. In case you haven't noticed, I added "IMO" to many of my points, which clearly states that this is my personal opinion and not some facts from heaven (the same applies to Keith's books and teaching BTW, with the advantage of his great experience).

 

You asked twice for my opinion about your thoughts and I gave it, with much details. I had the feeling we're having a discussion about body position and weight transfer before turning, during and on turn exit. I've posted my thoughts on the subject and my interpretations.

 

If you think it's worth commenting, pls do so. If you don't find it interesting, or you think it's not worth reading because you interpret it as contradicting to CSS methods, just skip it.

 

'nuff said.

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I guess I should write and edit my posts on a word processor before posting them. I forget that someone on the other side of the world might be lurking to respond before I have five minutes to finish editing... lol.

 

In any case, I apologize. I missed all the "IMO"'s I guess.

 

For what it is worth, I disagree wiith your entire post, as do Keith Code's teachings... IMO.

 

I suggest you re-read the books.

 

Cheers

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avih,

 

I've re-read your post with another cup of coffee and perhaps I judged it too quickly or harshly. Again I apologize.

 

I'll give it another read when I come home from work tonight.

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1st pic is mid corner closer to the exit, 2nd is mid corner, 3rd is closer to entry. My feeling about the crash was that because I hung off too much early in the corner and then never slid up in the seat while exiting, I didn't have enough load on the rear. I think it contributed to it spinning up. In the school on day 2 my coach wanted me to ride around not hanging my ass off, and work more on my upper body position. I've been really focusing on that but have caught myself going back to my old ways at times. Here is a pic of Ben Spies at VIR in what appears to be mid corner. seems to work for him!

FriAfnoon18.JPG

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Hi All,

 

I'm personally quite proud of this forum, and the members. The general tone is good, friendly and helpful, good questions get asked, and people have a place they can ask questions and not get slammed or made fun of.

 

Been off the forum (non stop schools) for over a week, and this thread was referred to me. Glad it got back on topic, though I can't find Meat, he might be gone and that's not what we'd like to see. I'm going to ask all to keep their manners in. Some of the comments came across pretty sarcastic. I haven't had much need to edit or delete, and I'd rather not. Opinions are one thing, but others should be allowed to have their own, and not made those appear to be wrong or stupid. Interestingly enough, people don't seem to learn well that way, know what I mean?

 

Please do continue the posting! If it gets a bit off track, please do let me know, e-mail is best, but my cell phone is always on: cobie@superbikeschool.com 818-404-2453.

 

Best,

 

Cobie Fair

Chief Riding Coach

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Sleepr. Your body position is great in pic #1, too upright in #2, and OK in #3. #3 is a good position to work with (you can reference Hodgson and Mladin for more upright positions), and it looks like you have the same problem as the other 95% of us do: consistency. I can post 2 (probably closer to 3) pics with bad position on my part to every 1 good one they took. That's why we practice. I do notice that it looks as if your toes are on the verge of dragging with each knee drag. If that is a problem, your position is good enough, and you might just want to try bringing your foot back a little more on the peg. Might I just say that I wish I had your position in pic #1.

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Apology accepted.

Thank you.

 

IMHO, that post does include some interesting issues for discussion, on topic.

Indeed, I'm sure it does. I wasn't really awake yet when I quickly skimmed through it over first coffee this morning on yet another night of five hours sleep. Unfortunately, I am unable to devote the time that it deserves tonight either.

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I tried to compare Ben Spies' pic (good one sleeper :) ) with a pic of mine from a similar perspective. Had to flip my pic horizontally to make it easier to compare (mine is originally a right turn) and I can see few noticeable differences:

 

FriAfnoon18.JPG

 

f_IMG5719HF80m_ce7ff28.jpg

 

- Obviously, he has a much steeper lean angle than me

- He hangs off way more than me

- His butt is completely out of the seat

- His upper body "plane" is diagonal to the bike (vertical to earth), while mine's parallel. Probably an outcome of hanging off more?

- Similar outer foot position on the outer peg

- I think his outer knee doesn't touch the tank, mine does. I don't want to change that for now as it feels comfortable to me to be locked to the tank.

- His inner ankle position is very different than mine. His is almost vertical, mine is almost horizontal with the ankle bent a lot.

 

I think the last point is what I was looking for. The other points are clear and I'm mostly aware of them (whether they're OK or need improving). The last point about inner ankle position is something that I wasn't aware of.

 

It always felt a bit strange to me that I have to bend the ankle so much to be able to keep my toes (and not the middle of the foot) on the peg, but I thought it's due to my height. Maybe it is and maybe it isn't, but it's definitely something I should spend some attention at. I know that it feels to me that I have much weight in the inner peg, and now that I think of it, maybe it's due to the stress on the bent ankle. But if the ankle is more "open" and the foot more vertical, how does that supports my weight? bahh.. gonna have to experiment with that.

 

Good me for noticing something new ;) and thanks again for the pic sleeper!

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Thanks for the comments Hubbard. I noticed the toe position as well and am going to work on that. It's funny you say that about consistency, it is too true. I spent the last weekend in practice all day saturday in working on the drills from the school and was able to drop a second and a 1/2 from my lap time from the previous weekend. While I was riding on slicks for the first time I feel the go slow to go fast in practice approach was of more benefit than the tire change.

 

No problem Avih on the photo, sometimes surfing the web can be good for something!

 

Funny the more I think about riding, the more I understand my girlfriends position that I'm obsessed!

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Hi avih,

 

I've finally found enough time to respond in detail to your post of last week. Please take my reply in the spirit it is intended, which is to be helpful, not to be argumentative. I don't claim to know everything, but, for what it is worth, I've been riding for over thirty years, studying Keith Code's methods for over twenty years, and, I have several boxes full of podium trophies from more than ten years of racing. I only wish to share my experience for the benefit of others. That said, please forgive any untoward tone or verbage. It is not intentional.

 

It does, to a degree, because the 60/40 rule of thumb applies IMO only when the bike is at it's max lean angle and the acceleration/deceleration is neglectible.

 

Neglectible? For your benefit in learning English, there's no such word in our language. However, I could assume you meant either the closest word, "negligible", meaning small, insignificant, irrelevant... or invent a direct meaning for "neglectible", such as, able to neglect or ignore... perhaps? Which is patently untrue. Yes, the degree or rate of acel/decel which one is able to apply at max lean is less than at more upright angles, but, it is precisely for this reason that it cannot be neglected, ignored or considered insignificant. In fact, throttle control at max lean is perhaps the single most important (and least able to neglect) action that any rider ever makes.

 

 

In that case, the only force that applies is the centrifugal/pital one which is applied evenly to both wheels, and the weight/traction have to match it.

 

Um... huh? The only force? What about gravity? Regardless, you are incorrect that "it" (cornering forces) need to be applied evenly in this phase. As I (and Keith, and many others) have said, again, these forces need to be applied biased f/r to match the relative sizes of the contact patches as that is what determines the load bearing capacity of each tire during this phase.

 

This phase is usually quite short except for very long turns.

 

And... ? Are you implying (again) that time spent at max lean is "neglectible"? How and when you begin to accelerate largely determines how much you can accelerate and/or how much exit drive you can achieve down the straight to the next corner. The line you choose largely determines when you can start to pick it up to accelerate harder.

 

While breaking (sic-sp/braking), I think we need the bias to the front since that's where the main steering action takes place, therefore, we need as much weight and traction as possible there to steer the bike effectively. The rear traction plays a much smaller role in this phase.

 

Again, you are contradicting what you said in your previous post when you agreed that (theoretically) you would want to move the body toward the rear when braking to avoid overloading the front tire, the game under braking while leaned over or straight up and down, is to not overload the front tire in the process. The forward force of braking can move 100% of the weight to the front tire no matter where your body is. Moving rearward might theoretically increase the limit of braking force applied to cause that 100% shift. I don't really know, but, it sounds good. That said, making sure that there is enough weight on the front to apply the brakes is important. Simply rolling off the gas is generally enough to transfer the necessary weight in most situations, ie. you don't need to climb up on the gas tank before you apply the brake.

 

On the exit (which is a relatively long process , starting probably just before the apex) when we progressively accelerate, the rear tire needs more traction than the front beyond 40/60, because the rear tire needs the extra traction to support both centrifugal force and acceleration.

 

If we're at 40/60 and at the traction limit and we apply more throttle, the rear will beak loose IMO because it was at the limit already and can't support the extra force from acceleration.

 

 

(This section needs to be re-written due to lost copy during editing. No time now.)

 

While it is true, as we said before, that, like braking, having enough weight on the rear before accelerating might help prevent breaking the tire loose if you whack the throttle open hard. Throttle control is the primary factor and once we are in the process of accelerating, the optimum balance or relative bias between the front and rear is dictated by the relative size of the contact patches, front and rear at max lean. It is not so much a matter of more or less absolute weight on the rear tire when leaned over, it is a matter of how much weight compared to the front that will define the available overall traction/load capacity. That said, once you begin accelerating while leaned over, like braking, the trick is to not overload the rear tire, either with "weight" or cornering force, or with too much throttle. My point is that moving your body forward will (theoretically) allow more throttle to be applied to achieve 60/40 or optimum bias for max available traction, hence, max potential for acceleration.

 

If there is 40% weight distribution to the rear and 60% to the front, the amount of acceleration one can add will be limited or less than what it could be if it was 60/40 because the weight distribution does not match the contact patch distribution.

 

In general, the harder the acceleration, the more weight we need on the rear to have the traction needed.

 

Mm, not quite. You are looking through the eyeglass in reverse, so to speak. The more you accelerate, the more weight there IS on the rear because you are accelerating. The more you move you body forward, the harder (theoretically) you can accelerate and maintain optimum wieght distribution hence, maximum traction and max potential for more acceleration.

 

(continued)

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On corner exit process, few things happen gradually:

- The turning radius increases

 

No, it doesn't. Not if you apply the correct amount of acceleration to acheive 60/40 weight balance, the bike will hold a continuous line. Once you begin to exit and accelerate harder, exceeding 60/40, your line may widen.

 

- The bike straightens up

 

Not unless you steer it up by applying pressure to the handlebars.

 

- We apply more acceleration.

 

If we choose to, yes.

 

The front traction is only needed while leaning (and initiating a turn) as it gives nothing on a straight line (I don't count steering correction as relevant for this discussion). Therefore, as we exit the corner, more and more weight should and can move rearwards to support acceleration.

 

Should and can? Are you talking about body position? As we accelerate, more and more weight DOES move rearward as the result of accelerating, no matter what we do with our bodies.

 

As acceleration increases beyond a certain limit where 100% of the weight is on the rear, the body should be forward to prevent the the front from coming up, allowing to accelerate even harder (as long as the tires are good and the asphalt grips well). All these processes are, naturally, gradual.

 

OK, sure. But it is the leaning phase that is most important and critical to how much speed and acceleration we will be able to carry through the exit and on to the next phase.

 

It's all about balancing the traction needs at each phase. On entry we need mostly the front therefore it's probably 80-20 or more biased forward, while leaning we need both so that's the classic 40-60, on exit we need more and more of the rear, ending in 0-100 towards the straight when we only need the acceleration. And all gradually, smoothly and fast ;)

 

When and where and how we begin to accelerate at max lean is what will determine everything else. Hence, "it is all about" accel/decel at max lean. Everything begins and flows from that point. (Hence, why folks are posting photos and asking for advice about their body position at max lean.)

 

I hope this helps you to start to get an idea of the big picture, avih. There is so much more written about this subject in the Twist of the Wrist books, especially Twist II, elaborating on all the ways how what happens at max lean dictates how fast the rest of your lap will be. If you have any questions after re-reading them again, I will be happy to help.

 

Regards,

 

racer

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oops

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Thank you racer for your detailed respond, and for the time you took to relate to my post. For the record, I don't find this post of yours offending in any way so I think we can put this issue behind now. Your vast experience and that of other users of this forum is exactly the reason I'm here: to learn, And learned I have.

 

As you, I also like a good discussion. In contrast to you though, my experience is very limited (probably not more than 5 track days overall, some in a limited form) so I try to combine my little experience with logical analysis of situations, and theoretical (for me) knowledge from TOTW books and other sources. Therefore, when I say IMO, it means just that, and its definitely open for criticism and discussion as far as I'm concerned. The same goes for this entire post.

 

I also apologize for my typos and possibly for my syntax errors. I'm not a native English speaker, nor do I speak it daily. I believe negligible is the "passive" form (?) of neglect but my spell checker couldn't fix "neglictible" properly so I left it as is. You interpreted it correctly as I've expected. As for "breaking", oops ;) anyway, thx for your corrections, keep them coming.

 

Before I respond to your comments, let me clarify myself about some terms I've used, just to make the discussion clearer. Please correct me if I'm not precise.

 

- Weight balance of the bike is not body position. Weight balance as I referred to it is the ratio of the vertical force-interaction between front-wheel-to-ground and rear-wheel-to-ground. If the front wheel is off the ground then I refer to it as 0/100 weight ratio (100% of the weight is on the rear wheel). If the rear is off the ground, then I refer to it as 100/0. When I refer to balance in the form of X/Y, I put the front tire 1st (X) as in 40/60. Weight balance can be affected by BP, acceleration and the engineering of the bike itself.

 

I've read your entire post carefully and it did make me reconsider and organize my thoughts, and made me change my understanding of things. I agree with most of your corrections of my post: the inconsistencies you mentioned, the duration we stay at max lean angle (I agree it's not short at all), cause and effect of weight balance and acceleration/braking. I also Agree with your weight transfer comments, although for the sake of keeping this discussion and post focused (as much as it can be), I won't relate to them and will explain why. For the same reason I will also not relate here to the steering action itself. I do not agree with your claim that the turning radius keeps constant through the duration of max lean angle. This will be one of the conclusions towards the end of this post.

 

I will 1st describe my understanding of straight line physics (acceleration/braking limits how they're effected from BP) to set basis for the cornering section of this post.

 

 

My general understanding of things is that you cannot go much (if at all) beyond 100% weight on either wheel, either in braking or in acceleration. That's where BP can takes part. If your max theoretical acceleration is X(m/s^2) with a certain fixed BP (0/100 weight ratio), then its less than X if you sit more backwards, and more than X if you sit more forward (in each case, after we're at 0/100 weight balance). This is due to the angle formed at the rear contact patch between the combined CoG and earth (While braking: front contact patch). If you move your body forward while accelerating, you can accelerate at a larger rate than X before we reach this maximum 0/100 weight ratio. Same goes for braking. Moving backwards on the seat allows greater braking force to be applied before we reach the maximum 100/0 weight ratio, after which the rear comes off the ground and we cannot brake harder.

 

It's obvious that the weight shifts backwards due to acceleration and forward due to braking. However, the amount of acceleration/brake-force that can be applied at any certain time is related to overall weight balance and maximum vertical force at each wheel.

 

IMO, 3 factors can limit the rate of acceleration that we can apply:

 

1. Spinning of the rear wheel before we're at maximum possible weight on the rear (before 0/100 balance on a straight line)

2. Spinning of the rear wheel after we're at maximum possible weight on the rear

3. Front wheel coming up

 

(In braking: locking the front before we're at max front weight, locking the front after we're at max front weight, and the rear coming up).

 

- The 1st is related to the speed/balance/efficiency of the weight transfer process (combination of amount of acceleration and BP)

- The 2nd is related to the maximum theoretical traction force from the rear (rubber/asphalt type, weight of the bike+rider) and rate of acceleration

- The 3rd is related to BP and rate of acceleration. we need as much forward BP as we can to make that X as large as we can before the front comes off the ground.

 

Although I think the 1st reason (weight transfer process) is both very important and frequent enough in practice, it can occupy an entire discussion by itself on one hand, and OTOH it can be discarded for the sake of this discussion of absolute limits by making all actions more progressively. It is greatly affected/improved by experience IMO. I'll disregard it for the rest of this post as it puts more variables into an already complex discussion, and it can be neutralized by changing the amount of acceleration/braking in a much slower rate. It will obviously harm lap times, but it's also unrelated to the maximum forces that can be applied at any given "fixed" state of the bike. So for the rest of this discussion I'll assume optimal weight transfers, and concentrate on the limits after we've reached "steady" states of weight balance.

 

So that leaves us with the 2nd and 3rd points.

 

I believe the 2nd and 3rd points are 2 implications of the same cause: we're at 0/100 balance (if on a straight line) and we try to accelerate more than the theoretical maximum. If we increase the rate of acceleration beyond the theoretical maximum too fast, the rear will spin. If we increase it slower beyond the maximum, the front will come up. The exact rate of speed of acceleration needed to differentiate between 2 and 3 is a direct function of the available traction (only forward on a straight line), and combined mass and CoG of the bike+rider: the smaller the mass or higher the "grip factor", the easier it will be to wheelie, the lower and forward (in braking: backwards) the CoG , the easier it will be to spin (in braking: lock) and vice versa.

 

IMO BP can affect the 1st point and the 3rd point, but not so much the 2nd point.

 

I think I didn't explicitly relate to "overloading" either tire although I probably related to this effect implicitly. Speaking of which, could you define "overloading" as you refer to it? I can interpret it as either closing the forks due to excessive braking force, not allowing enough weight transfer before we apply more braking/acceleration, apply more brake power than possible with current grip factor (regardless of forks state), excessive angular velocity which causes either wheel to run wide, etc. I think I'll be able to better relate to your post if we're clear on the terms we use.

 

This was a straight line discussion (well.. at least my current understanding of things). I believe it is essential to try and understand straight line physics before we can discuss the extra complexity that cornering adds. At least for me, it makes it easier for me to "combine" and add the effects of cornering into this existing understanding.

 

While leaning, on top of the vertical force (fixed overall but balanced differently on the front/rear depending on BP and acceleration/braking) and acceleration/braking forces, we also have a centrifugal force. The angular velocity of the bike and the bike's+rider weight define the amount of absolute force in that direction (perpendicular to the direction of the bike's progression). The angular velocity by itself is the only factor affecting the the amount of leaning needed to balance this force.

 

Because this centrifugal force needs some traction resources to balance, that leaves less absolute traction resources to accelerate/brake. The larger the angular velocity (and directly related: lean angle) is, the larger the amount of traction needed to be devoted to keeping us on track and from sliding sideways, and the less freedom is available for acceleration/braking needs.

 

In contrast to acceleration/braking on a straight line though, where we can shift 100% of the weight to one wheel for maximum effect, leaning requires a different "tactic". Now we're no longer interested in maximum acceleration/braking force, but we're interested in maximum centrifugal traction. If we want to achieve maximum cornering rate (= max angular velocity), we need maximum combined traction from BOTH wheels to achieve maximum absolute centrifugal traction. And this is where the 40/60 rule comes in handy. I agree that 40/60 (or a similar figure) is the balance that would give us most centrifugal traction (derived from the size of the contact patches). So how do we achieve this balance? Combination of BP and acceleration.

 

 

To achieve maximum angular velocity/traction, we need the weight to be balanced 40/60. BP would affect it to some degree (I'm guessing not more than 5%), but acceleration is probably the most important "tool" in this regard. It has to be mild and steady such that the weight moves backwards from the natural 50/50 of a still bike+rider, to 40/60 of an accelerating bike (let's call it "40/60 acceleration"). As long as we're at our max lean angle, the same acceleration should be kept, to keep us at 40/60 balance.

 

The closer we are to the maximum possible absolute angular velocity (and lean angle), the less reserves of "forward traction" we have, and therefore the less freedom we have to change that balance and our 40-60 acceleration, or else, one of the wheels will break loose.

 

To cause one of the wheels to break loose, it's again one of the 3 reasons I've stated earlier in this post, with two differences:

 

1. There's much less traction that can be devoted to acceleration/braking, due to the resources devoted to centrifugal traction, and we're therefore mostly limited to spinning the rear (/"locking" the front) and we don't have to worry about the front coming up because there isn't enough driving traction left to make it happen (It may happen later though, when we're more straight on the last phase of corner exit, again, depending on grip factor of the tires/asphalt).

2. There's now a new 4th possible reason: We can also lose traction sideways (due to centrifugal force) on either wheel.

 

Since the 3rd reason is irrelevant here, and we're neutralizing the 1st one, we're left with the 2nd and 4th reasons.

 

To get to the 2nd reason (spinning the rear due to more than max possible forward traction or locking the front for the same reason): accelerating at a too fast rate will spin the rear, braking with the front at a too fast rate will make the front lock. "Too fast" is very small here since we're at very little "forward traction" reserves now. That's why we need the throttle control: to keep the acceleration as fixed as possible.

 

To 4th reason (sliding sideways) comes into play when we have more angular velocity than either tire can hold. This can happen if we're at 40-60 acceleration but we lean (make the angular velocity higher) more than the maximum possible: both tires slide (I guess this one is quite rare?) or if we get closer to maximum lean angle but we're accelerating at less than 40-60 or closing the throttle to get the same result (more weight on the front, it will break lose sideways 1st) or if we're getting close to max lean angle at a higher acceleration than 40-60 (more weight on the rear, it will break loose sideways 1st).

 

So to maximize angular velocity, we need that 40/60 fixed acceleration as long as we want to keep max lean angle. This brings an interesting issue of what "cornering speed" is. Derived from this analysis, we can see that this is a problematic term, since the cornering speed is not constant through the entire "max-lean" duration. To have a constant lean angle and angular velocity, we need constant acceleration. But cornering speed is not constant, and neither is the turning radius. Corner speed gets progressively faster and the turning radius gets progressively bigger WHILE we're at max lean angle.

 

This brings me to your claim about widening the arc/radius. As it turns out both from my analysis and from TOTW books (acceleration is required throughout the entire "max lean" duration), this 40/60 forward acceleration is required for max lean angle. If lean angle (and angular velocity) is kept at max constant for this entire phase, but the bike is going faster and faster (40/60 acceleration), the arc MUST widen since the bike cannot keep the same radius and lean angle while going faster and faster.

 

As we exit the corner towards the straight and straighten the bike up, the angular velocity decreases, more traction is available for acceleration, the arc widens at an even faster rate (infinite arc on the straight) and reason 3 comes back into consideration.

 

Phew.. this was probably my longest post ever on any forum. Please excuse me that I haven't directly related to all of your points (at least I agree with most). As it turned out, I was sorting my thoughts and understandings of cornering while writing, relating directly to your points less that I've intended. However, I did enjoy writing this post very much, and I think it presents the issues of cornering limits (excluding issues of the process of weight transfer itself and steering action) both in a manner that complies with the facts/tips/instructions of Keith's books, and in a manner I can relate to with reasoning.

 

Again, my theory and understanding are open for discussion by anyone.

cheers.

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:blink:

 

Good lord. It took me a week to find a time slot to attempt to reply properly to your last post and I still ran out of time before I could finish editing for clarification, ie. I'm still not finished replying to your last post! It's probably going to take me a month to find the time just to READ this one! :rolleyes:

 

Time.

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avih,

 

I have finished reading your last post and I find your analysis right on the money in all respects.

 

There is one point of clarification I would like to add for the sake of those readers who might not have a clear grasp of the difference between speed, (fixed) acceleration and the relationship to throttle position which they imply. Specifically, as you know, acceleration is a term defined as (ΔV/T) or the rate of change in velocity or speed over time. To avoid any terminology issues among any pedantic minded scientists here, I believe that in scientific circles, for the sake of mathematical convenience, acceleration can be termed or graphically represented as positive or negative; but, for our convenience, we regard all acceleration as positive and rely on the term "deceleration" to indicate the opposite. So, "fixed" or constant acceleration indicates a constant rate of increase in velocity or speed over time. That said, there is a terminal velocity for any discrete position of the throttle, hence, fixed or constant acceleration implies continuous change or increase in throttle position. That is, to maintain a constant rate of increase in speed (to maintain a constant 60/40 weight bias), we must continue to add throttle (smoothly and slowly).

 

As to your conclusion re: constant radius, I will need to think some more about it. My gut says it may simply be a matter of "neglictible" significance at 60/40 accel. In other words, for our intents and purposes, the rate of accel is so small and the proportional difference in radus so small as to be imperceptible or nearly so. Or, it may be something else. In any case, what you said makes sense and I will have to think more on it.

 

Time.

 

r

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Ahh.. new term is coined, neglectible ;)

 

Indeed, I have not estimated this "40-60 acceleration" in practical terms. It could be interesting, I'll put some time into it a bit later, and try to put it into more accessible terms of percentages/lean angle/etc. IIRC, in TOTW2 there's an estimation of this amount of acceleration in a straight line.

 

BTW , Interesting corollaries of this conclusion are:

 

- By riding round a fixed circle at a constant radius while very slowly increasing speed, you cannot reach maximum lean angle, since as you get close to it, the 50-50 (appx) weight balance of fixed radius/speed with no acceleration prevents you from taking advantage of the maximum centrifugal traction the bike can offer. You will lose the front 1st because it would have higher centrifugal load than it can bare, while the rear will keep tracking perfectly.

 

- If cornering without accelerating, you're at risk of losing the front, especially if you're close to the max lean angle. Even more so if you shut the throttle off or even just ease it while turning.

 

 

If indeed this conclusion and corollaries are of non-negligible proportions, then this theory of maximum traction availability only in an ever widening arc goes very nicely with late apexing.

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I'm not sure I follow your first corollary. You start off describing acceleration and then refer to constant speed. I'm missing a connection somewhere.

 

If you accelerate a little too much (not enough to spin the rear tire) then too much weight will transfer to the rear and the front will become too light to take advantage of optimum traction. However, I'm not sure we can make a blanket statement about which wheel will slip first (rear overload, front underload) without knowing more about the situation. That said, generally speaking, most mid-corner falls are low-sides unless the rear spins up.

 

If you don't accelerate (enough) or decelerate, then yes, the front will overload and slip first.

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That's why I said accelerate slowly. Let's say, 1MPH more on each lap. For the sake of the weight balance, the acceleration is negligible and therefore we're very close to 50-50 at a constant speed. This ratio prevents us from utilizing the full centrifugal traction potential of the bike (more weight on the front than the optimal balance), hence, we will lose the front before we reach max possible lean angle.

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