Learning to trust the lean??

[russell_bynum]

Thanks for the reference & comments though. Somebody has to know. My guess right now is the need for acceleration is from aerodynamic forces, but still should be of little use to newbys at reasonable speeds.

 

Don't you feel it when you're riding?

 

I mean...I'm not a scientist, engineer, or math whiz, but you don't have to be the head cashier at Walmart to feel the difference in how the bikes handles when you corner off the gas, on neutral throttle, or on the gas.

[David]

You're just using lots of words.

[nrp]

But why otherwise?

[nrp]

I just had another revelation which canceled my previous one a couple of posts above. The longitudinal effects of aerodynamic loads are NOT canceled by acceleration in turns, they are compounded by it. Disregard my earlier eureka.

 

I really don't feel the positive effects of acceleration in turns. I enjoy acceleration at all times, but I don't feel it helps me any more when making a curve.

 

There has to be a logical reason. What is it?

 

nrp

[russell_bynum]

I just had another revelation which canceled my previous one a couple of posts above. The longitudinal effects of aerodynamic loads are NOT canceled by acceleration in turns, they are compounded by it. Disregard my earlier eureka.

 

I really don't feel the positive effects of acceleration in turns. I enjoy acceleration at all times, but I don't feel it helps me any more when making a curve.

 

There has to be a logical reason. What is it?

 

nrp

 

Did you check out the book that David suggested?

 

Lacking that, take your bike to a parking lot and play with it. You don't need a degree in advanced physics to feel the difference.

[ShovelStrokeEd]

Except on bikes like mine which produces down force at the front end, or considerably less lift. It was designed with ca 180 mph top speeds in mind.

 

Niel,

You do realize we are not talking about grabbing a handful of throttle here. Rather, it is rolling on just a bit of throttle as you turn the bike in to get it into a neutral state during, or slightly after, turn-in. I find it quite useful, and the difference in feel is pretty dramatic. I do it even on low speed turns. It fits with my riding style. In addition, every instructor I have ever worked with or whose books I have read recommends the technique.

 

Might I suggest you experiment with it a bit more? Do keep in mind that there is a degree of throttle control required here, you more or less only change the tension within your hand, not crank in throttle using your wrist or arm. Pick a nice curve on some secondary road and take it at a speed that requires about 15 degrees of lean. Try steady throttle, trailing throttle and mild acceleration. Pay attention to what the bike is doing under you and pay particular attention to divorcing throttle inputs from steering inputs. I think that last may be why you're not feeling the benefits we all have talked about.

 

I don't have the calculus to solve multiple moving body and spatial relationships but I can figure out whether the car accelerating from an on-ramp is going to interfere with my path and move over in only a second or so. Learning to feel what is "right" is the same thing.

[nrp]

Give me some time to reply. I know a guru of motorcycle racing, now a F-1 racing team R&D manager with a Doctorate in AstroPhysics. I'm gonna shake his tree & see if we can get some answers. I'll post again then.

[russell_bynum]

Give me some time to reply. I know a guru of motorcycle racing, now a F-1 racing team R&D manager with a Doctorate in AstroPhysics. I'm gonna shake his tree & see if we can get some answers. I'll post again then.

 

Nevermind shaking trees...just go ride and see for yourself.

[nrp]

I have for 40 years & over 120K miles - on four Beemers & a couple of other brands. My wife only let me keep three (all BMW now) of them though.........

[russell_bynum]

I have for 40 years & over 120K miles - on four Beemers & a couple of other brands. My wife only let me keep three (all BMW now) of them though.........

 

Ok.

 

 

So...have you gone out and tested to feel the difference in being off the gas, neutral throttle, or on the gas while cornering?

 

I don't know the physics of it, but I know what I feel, and to me, the bike just feels better when I've got the throttle on.

[zbassman]

Man, when I posted this topic I thought it was a pretty straight forward question. I never expected the replies to include discussions of physics, mechanical engineering, calculus, and Marth Stewart

 

I'm not a scientist, never really studied physics or mechanical engineering and feel like I've done my best mathematics if I can figure out an appropriate tip at the local bar.

 

So, I would never be able to prove or disprove the assertion that rolling on throttle through a turn will or won't add stability to the bike. But it feels right to me.

 

However, I'm not sure if it feels right because it feels right or because that's what I was told in class and in the Hough books I've read, and most of the on-line stuff I've read and I've just really bought in to it.

 

But that being said I'm always open to new possibilities. For the next few rides I'll try maintaining a steady throttle through turns and see how that feels.

 

Since my original post I've been really paying attention to my posture, position, etc while going through turns. I've found a couple of weak points. For example I noticed that I am shifting my butt around in the saddle a little while leaned over. I've also noticed that some times rather than pushing on the inside grip I'm sort of pulling on the outside grip to initiate a turn.

 

So, I think part of my problem is that I am coming from riding a cruiser style bike, Suzuki Volusia. I think the Vol was a bit more forgiving of my poor riding habits. But the RT is more sensitive to body position, hand position, throttle input, etc. So my bad habits are just really being exposed.

 

Which is good, it gives me something to work on to improve my riding.

 

Thanks for all the responses and some really interesting reading.

[russell_bynum]

Excellent...glad to hear you're making progress!

[nrp]

Russell - Yes many times. I know I don't like to front-wheel brake in a sharp turn - because of handlebar yaw "snatch" effect (does that make sense?). But I can understand that reason from the steering head geometry. At low speeds I like to use only rear brakes for maneuvering - although my LT doesn't permit that. I don't like that, but accept it as something to be careful of.

 

But what is the corresponding reason for acceleration "feeling good" in a turn? It is a very weak (if at all) feeling I experience. I'm looking for an answer.

 

Thanks for hanging in here...

 

Niel

[Little Joe]

But what is the corresponding reason for acceleration "feeling good" in a turn?

Hey, it's like, you know, if it feels good...do it.

[ShovelStrokeEd]

Niel, sorry Joe, I hit the reply in your box.

 

Think I can describe the why it feels good thing, don't ask me for rigorous proof, the dynamics of motorcycle chassis function while in a turn, coupled with the use of throttle and all the various effects that has are beyond me.

 

Back to the why, moderate to light acceleration will counter the effect of centripetal acceleration trying to compress the suspension. This is more pronounced at hi-g cornering, of course, but it is there all the time. Trailing throttle will have the opposite effect and compress the suspension more. The spring rates are vastly different between the front and rear and, as the suspension compresses, usually more at the front than the rear, this changes both rake and trail at the front end and can make the bike feel nervous as a result. The mild extension of the suspension that results from acceleration, again, mild, counters this so the bike is not experiencing undue pitching moment during the turn. That is my theory anyway and it is based on playing with it over 50 years of riding and way too many miles. I have probably averaged close to 40K miles a year over the last 20 years or so on all types and brands of motorcycles. Rolling on the gas used to be essential on the old air heads, it was the only way you could keep those rigid mounted foot pegs off the ground.

[BWS]

Get new tyres.......you can think,discuss,practice all you want but,if your tyres are spent its(practice)usually gonna be headed in the wrong direction.IOWs it'll take steering efforts to keep the bike tracking through a turn,especially rty's(tighter).These "efforts" are for the most part destabilizing the bike,and in general screwing up.

 

Personally I'm WAY more comfortable shaggin a rty than lfty's.Simply 'cause of living here in the mnts.Lfty's have to be taken wide because of the inevitable dipsh*t linecrossers.Rty's are just plain,more fun.....has nuthin to do with a "weaker" side.Left's are more about hooking/squaring practice.

 

The very best of luck,BW

[nrp]

From my guru:

 

"(1) when coasting downhill in neutral, which I like to do for fun, there is no reason to accelerate out of a turn and it still makes for smooth and fun riding.

(2) acceleration slightly enhances line stability as the bike pitches back slightly, causing the trail to increase which slows down the steering. Too much pitching though will take load off the front end and can cause a wobble instability - this happens on racers when the front end gets very light with still a bit of slip angle applied - lateral forces goes off-on-off-on as the front wheel dances on the ground, causing the wobble.

(3) acceleration and the higher speed is causes require a wider "orbit" for the same lean angle. This is a nice way to increase the line's radius on the exit, making a better line through the turn."

 

Personally I think effect number 2) may be the most significant, but I still think it isn't needed in the BRC.

NRP

[russell_bynum]

Personally I think effect number 2) may be the most significant, but I still think it isn't needed in the BRC.

 

So, we've established that it makes the bike more stable in the corners, but you still don't think it is worth teaching?

 

Maybe we should approach this a different way...

 

Why not teach it? Since it is pretty widely agreed/accepted/proven that it is better to go through a turn on the gas than off the gas (or neutral throttle), then why would you not teach it?

 

There are some things MSF teaches (or doesn't teach), which are not the best way to do things, but there are reasons to teach that way. For example, MSF doesn't want you to cover your front brake, and they want braking to be done with all four fingers.

 

Covering the front brake is the better way to go since it reduces reaction time, and on the majority of modern bikes, there's no reason to use more than 2 fingers (I could engage the ABS on my R1100RT with one finger, for example.)

 

But...MSF has reasons for teaching that way: They don't want newbies to get panicked in a turn and grab the front brake, and they know that there are some bikes where if you brake hard, the lever can come far enough back that it traps your fingers between the grip and the lever.

 

So...there's a reason for teaching the way they do even though it isn't necessarily the "best" way for a more experienced rider to ride.

 

But why would you not teach newbies to roll on the throttle in turns?

[ShovelStrokeEd]

Further on #2, the wiggly thing he is talking about is actually head shake and yes, it is caused by the front end getting light under extreme acceleration. One need not apply anywhere near that much throttle in a turn and still experience acceleration all the way through the turn. In fact, for a good percentage of the bikes on this forum, they don't produce enough power, in all but the bottom 2 gears, to reach the point of head shake. By the time the rider gets to where he is applying full throttle just past the apex of a turn, he will have developed the skill set to deal with a little head shake anyway. For the new rider, mild acceleration when exiting a corner just makes sense so long as we are not dealing with a new rider on an R1 or a GSXR 1K.

[russell_bynum]

Further on #2, the wiggly thing he is talking about is actually head shake and yes, it is caused by the front end getting light under extreme acceleration. One need not apply anywhere near that much throttle in a turn and still experience acceleration all the way through the turn. In fact, for a good percentage of the bikes on this forum, they don't produce enough power, in all but the bottom 2 gears, to reach the point of head shake. By the time the rider gets to where he is applying full throttle just past the apex of a turn, he will have developed the skill set to deal with a little head shake anyway. For the new rider, mild acceleration when exiting a corner just makes sense so long as we are not dealing with a new rider on an R1 or a GSXR 1K.

 

Exactly.

 

I don't even ride agressively enough on the race track to get my CBR600RR to head shake, and that's a fairly powerful, fairly light bike with very agressive steering geometry.

[nrp]

I'd rather the Basic Rider Course had taught my daughter (and covered it when I took the course) how to handle a heavy bike with the foot brake when starting on a hill. She no longer rides after several dumps.

[russell_bynum]

I'd rather the Basic Rider Course had taught my daughter (and covered it when I took the course) how to handle a heavy bike with the foot brake when starting on a hill. She no longer rides after several dumps.

 

Hm. OK.

 

Correct me if I'm wrong here, but don't they teach you to stop with both brakes, and put your left foot down while leaving the right foot on the brake?

 

That's pretty much the skill you'd need for that, right? I mean...actual practice on actual hills could be tough to come by since MSF usually works out of parking lots, and they're generally as flat as possible.

 

And I'd be totally opposed to having them teach newbies ANYTHING with heavy bikes. Let them start with small lightweight bikse like the DR200 and the 250 rebel and move up to big bikes when they're ready.

 

It sounds to me like your daughter needed to start on a lighter bike before moving to something heavy.

[nrp]

Things may have changed but we both were taught to hold the bike with both feet down after stopping. I got nowhere objecting to this - or even trying to explain it to my daughter on her Honda Silverwing.

[russell_bynum]

Things may have changed but we both were taught to hold the bike with both feet down after stopping. I got nowhere objecting to this - or even trying to explain it to my daughter on her Honda Silverwing.

 

Ah.

 

Well...a couple of things about that:

 

First...you're going to have trouble objecting to MSF's curriculum. When you think about it, they really can't afford to be arguing/debating the merits of different techniques ad infinium, so they have their curriculum, and that's it. Period. It doesn't deal with every possible situation, but it works pretty well on average. Some instructors will talk, off the record, about things that aren't on the official curriculum, but that's pretty much hit or miss based on who you get.

 

That said, I thought the Silverwing had an automatic transmission, and brakes on both sides like a bicycle. No?

[nrp]

The Silverwing was a 500 (600?) cc mini-Goldwing. It had the longitudinal crank and two cylinders in a vee like a MotoGuzzi. It was water cooled, and maybe a little heavy for my daughter, but at least it was fully roadable. She would dump it on every stop sign on a hill, trying to hold it from rolling with her legs.

 

My suggested curriculum additions to the BRC would include how to handle a motorcycle just rolling it around in a garage or parking lot i. e. how the front brake causes major roll input when the steering is cranked over (at least to expect that). I also add the way to start a heavy bike on a hill (how in general to use the front and/or rear brakes to their full effectiveness). Also thoroughly explain the psychological effects of countersteer vs perceived inputs in an emergency situations.

 

To make more space for it I'd delete the accelerate-around-a-turn, and maybe the sweeping-of-turns for higher speeds.

[grayghost]

I know the BRC instructs you to stop "with your head up, looking straight ahead". This way the handle bars will be straight. I also remember in an "intermediate" an instructor grabbing the handlebars from the front of a students bike to demonstrate how the bike would be "tippy" if it was stopped with the handlebars turned.

Like a previous poster said there's additional information/pointers/tips depending on the individual instructor.

[EffBee]

I've been reading this thread and trying to understand just what it is you're looking for. I guess it's quantifiable data. I'm not an engineer, so I can't provide that. However, let me give you my perspective, interpretation and assessment of what I "believe" is the value of accelerating through a turn.

 

First, I'd like to establish what "accelerating" is in this context. I believe it to be a positive load on the engine/drivetrain, however small. That being said, I think the issue is being described as improving stability when perhaps a more accurate description would be that such positive load eliminates a variable and provides rider control over one more element which can be used to adjust the attitude and the arc of a bike through a turn.

 

I've always felt that any corner (at speed) is a controlled fall. We steer the bike out from under the straight line we're traveling (countersteering), and allow gravity to pull us downward. Then we counter that gravitational pull by steering INTO the direction of the fall, and in the process balance (ideally) the two forces. I'm sure that as an engineer you are aware of many more forces in play, but bear with my thoughts a bit longer.

 

A motorcycle that is leaned over off the tallest parts of its tires, and which is accelerating, tends to want to stand up. This can be minimized or exacerbated by steering geometry and tire profile, but generally I believe that the bike is trying to climb back up its tire tread onto the highest part. For that to happen, the bike has to be straightened up (at least to some degree).

 

So here you have a vehicle that is falling, and the forces causing that fall (gravity) being countered by the force of the arc steering back into the fall. Is that all there is? No, not if you use the engine as a variable load to help lift (or neutralize the fall of) the angle of the bike.

 

Piston engines, particularly in these lean-run times, seem least smooth at neutral throttle. It's virtually impossible to hold a steady, non-load rpm. And given the dirvetrain slack that's built into primary drives, transmissions and final drives (chain or shaft), there's a small amount of no-load room there for a part-throttle engine to wander, stumble, burp, hiccup, surge or cough. Yet, as it wanders through a range of part-throttle rpm, it may suddenly take up all the drivetrain slack, either toward the acceleration or deceleration end of that slack, and perhaps even both within the same corner or even a section of a corner. Bumping up against these limits then introduces either accelerative or decelerative forces into what has heretofore been a balance of gravity vs. arc (again, pardon my use of inaccurate terms, please correct if needed). This sudden "introduction" can upset the cornering balance.

 

By putting a positive accelerative load (however light) into the engine, one takes up all of the drivetrain slack, thus eliminating the interruptive force (either way) that can occur when that slack is taken up and released by a part-throttle engine. Now, instead of an interruptive force (which we're not sure is going to have an accelerative or decelerative input), we have taken this variable out of the equation and turned it into a controlled input against which we can counter-input (via lean angle, body weight transfer, etc.) and create a smoother balancing of the bike.

 

Again, I may be full of crap engineering-wise. But that is how I use a positive engine load when I corner. . .to eliminate an interruptive variable and turn it into an input I can control and use to adjust the balance of gravity vs. arc in a corner.

[nrp]

EffBee - You raise an interesting and possibly valid point - To eliminate the disturbing effects of driveline snatch during turns.

 

Otherwise, except at parking lot speeds, maintaining the upright posture of a motorcycle is accomplished mostly by the gyroscopic moments generated by the front wheel rotational momentum, and not really by the rider.

 

Experiments have been done with bicycles in which the front wheel has been fitted with a contra-rotating flywheel to cancel out the gyroscopic momentum and steer resultant steer head torques. I recall that made the bicycle nearly impossible to ride - especially at speed.

 

Another thought is that motorcycles at speed have enough drag that fairly substantial power is required just to maintain speed - enough that driveline snatch is already eliminated, unless the bike is going downhill.

 

The reason still escapes me - even the above guru's explanation seems shaky at best. Interesting though.

 

THX - nrp

[Quinn]

Just finished re-reading David Hough's book. He says that the gyro effect is really minimal and the bike's tendency to travel straight and upright is mostly from the rake and trail. The "contact patch" behind the pivot point of the front tire does almost all the work. Of course, he also reccomends rolling on the throttle in a curve.

[russell_bynum]

He says that the gyro effect is really minimal and the bike's tendency to travel straight and upright is mostly from the rake and trail. The "contact patch" behind the pivot point of the front tire does almost all the work.

 

There's no question that rake and trail are a big part of this whole thing, but I would guess that the gyroscopic forces are fairly substantial as well.

 

To demonstrate...go ride around at 10mph and try to make a quick direction change.

 

Then do it at 100mph.

 

Then 150mph.

 

I can tell you from experience that at 150mph, the bike does not want to change directions at all. If we were just dealing with steering geometry, why would the bike's willingness to change directions vary with speed?

[ShovelStrokeEd]

There is always momentum to consider here as well. The mass of the motorcycle traveling at 150 mph in a straight line is very much inclined to keep traveling in that straight line. Changing direction will require more and more force as the speed increases. Very basic physics with not much need for the complexities of gyroscopic precession or steering geometry.

[russell_bynum]

There is always momentum to consider here as well. The mass of the motorcycle traveling at 150 mph in a straight line is very much inclined to keep traveling in that straight line. Changing direction will require more and more force as the speed increases. Very basic physics with not much need for the complexities of gyroscopic precession or steering geometry.

 

Right...sure. But aren't the gyroscopic stabilizing forces generated by the spinning wheels a big part of that momentum that you have to overcome?

 

I wonder...what would happen (what would you feel) if you could suspend the front of the bike, then spin the front wheel up to speed and then tried to turn the bars? Would they be substantially more difficult to turn than when the wheel was stopped?

[Boffin]

There is always momentum to consider here as well. The mass of the motorcycle traveling at 150 mph in a straight line is very much inclined to keep traveling in that straight line. Changing direction will require more and more force as the speed increases. Very basic physics with not much need for the complexities of gyroscopic precession or steering geometry.

 

Right...sure. But aren't the gyroscopic stabilizing forces generated by the spinning wheels a big part of that momentum that you have to overcome?

 

I wonder...what would happen (what would you feel) if you could suspend the front of the bike, then spin the front wheel up to speed and then tried to turn the bars? Would they be substantially more difficult to turn than when the wheel was stopped?

 

Get a bicycle wheel and hold it by the spindle. Now get someone to spin it then try and move it. A motorcycle wheel is much more massive and spins much faster.

 

Andy

[russell_bynum]

There is always momentum to consider here as well. The mass of the motorcycle traveling at 150 mph in a straight line is very much inclined to keep traveling in that straight line. Changing direction will require more and more force as the speed increases. Very basic physics with not much need for the complexities of gyroscopic precession or steering geometry.

 

Right...sure. But aren't the gyroscopic stabilizing forces generated by the spinning wheels a big part of that momentum that you have to overcome?

 

I wonder...what would happen (what would you feel) if you could suspend the front of the bike, then spin the front wheel up to speed and then tried to turn the bars? Would they be substantially more difficult to turn than when the wheel was stopped?

 

Get a bicycle wheel and hold it by the spindle. Now get someone to spin it then try and move it. A motorcycle wheel is much more massive and spins much faster.

 

Andy

 

Right....it doesn't want to move. So....the gyroscopic effect is probably substantial on a motorcycle at speed.

[Carl_T]

Hey to Peter, who I met at the gas pump of Friendly’s in Rosendale.

 

nrp hello,

 

This is going to be a bit long in the tooth.

I have my own reasons for wanting a bit of positive throttle through my turns on the street and I believe I can say why. It is, as has been said, for increase in stability as well as an increase in bike recovery from slides do to road surface surprises.

 

I have a video to help illustrate where I’m going with my reasons for throttle on. It also illustrates my disagreement with the following quote.

 

In the extreme case, heavy acceleration causes the front wheel to lift causing the rider to likely lose control.

That’s a mistaken assumption as I’ve done it numerous times in the dirt and a small number of times on a road bike quite crash free. The video url I’m including clearly illustrates that, amongst other more valuable things.

 

Back to my main point though.

 

Absolute, maximum lateral traction is often far from your only concern when cornering a motorcycle. Any racer who rides near the limits of traction will agree that there are times when you intentionally give away a bit of margin over maximum side traction and break the tire loose a bit to accomplish other objectives.

 

Most street riders are quite far from maximum lean while riding and lateral traction only gets exceeded by them (with the bulk of street riders) when a slippery spot or some form of trap is run over, perhaps traps in rain, and also snow itself, should also be included. Otherwise normally, there is plenty of extra side traction left for a bit of acceleration.

 

In the You tube vid you will see Gary McCoy lift the front wheel in a turn, set it down, and lay the bike back into the turn to tighten up again. It is in slow motion, so you can watch bike dynamics more closely. You will see that the bike is not going into a front tank slapper with the front wheel lightened, and he is not crashing because he wheelied the bike mid turn.

 

More to my real point of why you add some bit of gas in a turn, this video is proof the bike continues to turn on the back wheel alone. That is an important observation to back up what I will say. The back wheel is helping the bike maintain an arc through the turn in the vid. The back wheel is helping turn the bike.

 

Here’s the vid on YouTube.

 

Gary Mc Coy slide, front wheel lift. http://video.google.com/videoplay?docid=...h&plindex=3

 

The main reason I want to show the vid is to illustrate that when the front comes off the ground, the bike continues in it’s cornering arc, even if it opens the arc up some bit (actually it can be steered some on the back wheel through body steering and turning the handlebars to use the front’s gyroscopic force, easier with lighter machines).

 

At any rate it does not just straighten up and shoot straight off the side of the turn just because front wheel steering has been lost the way a car would. Lift the front wheels of a car off the road, the car will go straight ahead. A bike is not like that.

 

Point: You have some degree of rear wheel turning going on once the lean was already in place. (yes, yes, yes, of course the front wheel steering is the main and most useful control I’m not saying otherwise).

 

The use of this rear wheel turning is valuable to a rider and a big “why” behind having some positive throttle (no not a lot of throttle, not wheelie throttle or anything near, SOME bit of positive throttle) in a turn.

 

To develop this further, I believe a wheel takes on additional work turning the bike, when more weight is transferred to it, and it does less turning work when weight is taken off it (relative to itself).

 

I believe that due to my experience with a motorcycle in the rough dirt of a Moto-Cross track, where these things stand out more clearly to the rider because of the extreme terrain conditions.

 

It is obvious to the Moto-Cross rider on an old time short travel suspension bike, that you can weight the front wheel, and the bike will react over the bumps and ruts more from what the front wheel is doing. You can conversely weight the back wheel and the bike will shift to reacting more in line with what the back wheel is doing. On the older short travel suspensions of yesteryear you could easily feel various percentages of this depending upon various weight distributions.

 

To take the extreme ends of the spectrum to better conceptualize, we will take riding the front wheel only, and riding the rear wheel only (I have been in both situations over rough ground as has any aggressive dirt rider/racer).

 

So, imagine standing your bike on the front wheel only (rear in the air) in a radically bumpy turn, and keeping it there (as if it were possible to do through most of the turn). We will say this turn has choppy bumps, broken pavement, deep frost heaved grooves parallel to travel, holes, sand, gravel, etc. in different areas of the surface while you did it.

 

Conversely imagine wheelying the bike round the turn, riding ONLY the back wheel through that same turn (this I have done through portions of a turn many times in the dirt).

 

Lets consider bike handling and stability in these two extremes, front only, and then rear only on the ground.

 

Now with the hinge of the steering head affecting things when riding the front wheel only, it will allow the surface troubles to deflect the wheel laterally with great ease, turning at the hinge of the steering head. When the front is forced laterally, it very easily deflects a good distance to the side as the bike moves forward due to the hinged headstock. This disrupts chassis stability, line stability, balance, etc. It also disrupts the rider who then may further input unwanted side deflections at the bars themselves. This sort of situation is a butt clencher, and also can be a prelude to a fall.

 

I have been in both situations in the dirt (front only in a rough turn and rear only in a rough turn) and believe me when I tell you the lack of a steering head hinge at the back wheel makes the rear wheel only situation a MUCH, MUCH, MUCH, more stabilizing force through the turn.

 

The rear wheel has no vertical hinge like the front steering head, SO forces trying to deflect the rear wheel laterally, then move through the swingarm, they find no lateral hinge, and are damped to some degree through the mass of the frame and bike (or so it feels), rather than acted out in full at the wheel itself, as when these same forces act on the front wheel. Riding the back wheel is more stable overall than riding the front.

 

With both wheels down both are influencing the turning of the bike. If you shift weight on the front the rear has less influence than otherwise over stability (especially over rough ground and edge traps etc.). If you shift a little weight to the rear, the rears influence becomes some bit stronger.

 

So, if you shift a bit of weight rearward you are helping the rear wheel influence the turning a bit more and you take a little advantage of it’s stabilizing nature at that point. The rider can actually feel this through the bike, most especially over rough or problem surfaces. The effect is discernable even on smooth surfaces as well.

 

A very sensitive rider can feel the difference in even relatively small weight shifts like 5-10%.

 

As a real world example take a Moto-Cross bike and rider leaned in a very bumpy turn. If the rider coasts through the turn to try and maximize lateral traction, the front wheels numerous deflections over the choppy ground, will steer the bike as the bumps deflect it. This will deflect the bike from the riding line, unbalance the chassis, unbalance the rider, and additional destabilizing inputs could easily be transferred into the bars as the rider is destabilized, making a bad situation worse.

 

If instead (so long as there is extra side traction available for acceleration) the rider goes to the gas, the bike then goes through in a much more controlled fashion. The rear wheel gets to influence cornering more in this situation and there is less unwanted front hinge steering going on. The rider gets destabilized less and the bike goes through the situation far better.

 

This was true for motocross bikes even when going in a straight line, way back in the days of 3 inches of rear wheel travel.

 

On the gas hard going straight through the bumps shifted the bulk of directional influence to the back hinge-less wheel, and the bike would track through worlds better than if the rider tried running through with neutral throttle where the front hinged wheel would then have a larger influence. As a matter of fact trying to even go straight through the rough with an old Jawa CZ on neutral throttle or throttle off, would have you spit into the weeds on your backside. Where riding through with the gas on and most of the weight to the back wheel, got you through fine even if you did hop side to side a lot.

 

Of course in a turn, lateral traction available at current lean angle, is a limiting factor for how much gas you can give a bike.

 

At any rate, if you load the rear wheel with a higher percentage of weight, it takes on a greater scope of influence in the turn (with the extremes being the rear lifted off the ground nose down, and the front lifted off the ground nose up).

 

I say this rear wheel turning stability is an important reason to load it some practical bit more in a turn by opening the throttle a bit. It is one of the “whys” behind adding a bit of throttle in a turn, and the reason the bike “feels” more stable under gas (because it IS under a bit more rear wheel stabilizing influence).

 

This is why even a newbie should come into the turn slow enough (and run a late apex line, which helps allow throttle roll on through a turn. If the newbie should run into frost heaves, square edged bumps, edge traps, deep parallel grooves that have not been filled with tar, or ANY deflecting thing of any sort at all while they are in the turn, they will already be in a more bike stable mode of travel. They will be less likely to go off line because of surface problems, or fall because of them.

 

This rear wheel stabilizing effect, is why, if you drop your front wheel into a choppy or rutted surface mid turn you are better off adding a little throttle in order to be more likely to get out of it OK. That’s so long as you are not already leaned all the way down scraping hard parts.

 

This is why there is that well known old adage, “when in doubt gas it.” When in doubt gas it to minimize the effect of the steering head hinge on the bike, is a part of the explanation for the old saying.

 

Being light on the bars (to minimize unwanted steering inputs) and being on some gas is the most stable motorcycle condition available IF there is traction enough to support lateral forces.

 

There are additional good reasons to be on some gas in a turn.

 

Lets say the newbie rider is doing what he’s been taught and is gently rolling on some gas through a turn. They miss seeing an approaching slick surface trap (or they target fixate on it) and run over it (say a patch of sand, gravel, oil, anything that lessens traction). Lets say the rear lets loose and slides the most over this slick spot (like my Bandit Motorcycle that I’ve been riding lately, it always lets loose with the rear out most often over slick stuff). IF the rider freezes the roll on, holds the throttle steady even though power is still being applied to the sliding rear wheel, and avoids stiffening up on the bars, allowing the bike geometry to turn the front wheel into the skid, this situation will give the greatest likelihood of a smooth re-grip of the rear when good traction returns after the slick patch. A chopped throttle risks a potential high side in this situation if the rear goes far enough out, since the rear will hook back up too quickly instead of progressively. Some throttle being on is most likely to help it hook up progressively if it can. Very little (beyond holding the throttle steady at status quo) will be required of the new rider since the throttle is already in a good place to help out with a smoother re-grip. It is then safer than having run through without throttle on.

 

Now lets take the exact same short-ish slick spot in a turn situation. Only this time the front radically loses traction and tucks (steers into the turn sharply) while the rear maintains more traction (like the SV650 that I am also currently running, it almost always loses traction over a slick spot by sliding the front, I have been in an extreme full tuck situation from deep sand mid turn on it and it has recovered due to my somewhat accelerative throttle setting, bar non intrusion, and good luck).

 

By reacting in the same way as needed for a temporary rear wheel traction loss, and not needing to learn anything new or different, the newbie rider will have a better chance of skating free of a low side “front slide out” fall. By halting the roll on, holding the throttle steady, and staying light on the bars allowing for bike self-correction from the bikes built in trail at the front, the bike has the better chance for recovery. By the rider not having to “adjust” something while traction is being lost, the bike will be the least amount disrupted and again the re-grip stands a better chance of being progressive enough to avoid a fall.

 

Counter steering is not only for tipping into a turn, but also for standing a bike back up. If the wheel turns into the turn more, the bike tries to stand up more (still countersteering). This is why if you are falling in during a low speed parking lot U-turn, adding throttle saves it. The extra forward push of added gas, pushes even harder against the front tire that is already turned into the turn, the bike then stops falling in as it tries to stand up a bit more. The rider saved falling to the inside through acceleration pushing on the front “countersteer” to stand the bike back up.

 

The same thing can be said for a higher speed, on the road slick spot turn, where the front slides and tucks (turns) INTO the turn. When that happens, the bike tries to fall down into a steeper lean due to the sideways front end slide (lowsiding the rider and bike). The tuck tries to save things and stand the bike back up. By the rider already having some throttle on, which adds additional forward force, the tuck tries to stand the bike up (recover) some bit more than if the rider was off throttle. The bike is already riding more of the back wheel in the turn as well. More so by some bit than if the throttle was off, and the back wheel in this case is doing well. This gives more stability and recovery time. The front isn’t overloaded due to an off throttle situation either, meaning it will be more likely to recover than if it was.

 

So, it really is good for newbies to learn to craft lines that allows for gentle slow throttle roll-on through turns. Additionally they need to come into turns at a slow enough speed, so slow gentle throttle roll-ons through the turn can be used as well. There are good reasons to do it, it adds stability and puts them in the best situation to handle surprise road surface troubles.

 

The above I have personally experienced. Now for the part I am not so clear on.

 

Tire traction; I’m assuming if a tire pulls 1G on a given surface that the only way more weight on it increases that 1G of traction is by deforming the tire to increase the contact patch, and forcing the tire deeper into the surface irregularities.

 

I’ve no idea how much extra traction it might get from that, probably only a little. It seems to me 1G is 1G whether it’s 20 lbs pushing down or 200 lbs. it still take an equal side force to break traction at 1G, so I can’t think of anything other than larger contact patch and deeper penetration into surface irregularity that would increase traction at that wheel when more weight is added.

 

Also it seems to be the case that; though a tire’s side traction capabilities can increase a some bit from more weight, that only remains so until too much is added, then the tire seems to get overwhelmed and the traction reduces. The same can be said for removing weight, while the traction is reduced “some bit” through weight removal, there seems to be an eventual point where traction then gets reduced a lot more. In other words there seems to be some range in operation when it comes to loading and unloading tires, before traction severely goes away.

 

I’d like to see some information on that subject if anyone knows of any on the net.

 

At any rate I am unconvinced that a larger contact patch will not give a bit better traction. If this were not true, we could run half inch wide road bicycle tires of the correct traction compound on our 1K cc motorcycles. Additionally if you are sliding the back end of a motorcycle under power, and you pick the bike up to a lesser lean angle, making a larger tire contact patch, you get more traction out of the tire.

 

So a modern day bike carries a tire with a relatively smaller contact patch up front, and a relatively larger contact patch out back. The average weight distribution of a bike at neutral throttle is close to 50%/50%, putting equal weight front and rear through a turn.

 

The larger rear contact patch should be fully capable of carrying a small amount of acceleration/rear weight shift, even at radical lean without adding troubles. I think that is due to an already larger contact patch, an increased contact patch due to additional weight, and also due to the tire being pushed deeper into surface irregularities in the blacktop.

 

 

As an example, in a minimum traction situation such as ice, any attempted acceleration will reduce the lateral force capability of each wheel, with the front wheel being the first to slide out laterally while accelerating.

 

As to extreme slick stuff like ice and neutral throttle; this slick a surface is it’s own thing. You don’t get weight shift on ice when you accelerate like you do on blacktop, so any additional contact patch size benefit is forfeit. There are no surface irregularities for the tire to be pushed into either. Actually traction is so horribly low on ice that even a small bit of added throttle can be uncontrolled and act like grabbing a complete handful on blacktop, There is no way to consistently modulate any accelerative force on something that slick. Tires behave differently on ice than they do on blacktop.

 

I have ridden bikes on ice under throttle in a turn in the past. I have fallen on my butt due to massive rear wheel slides, decidedly NOT front slides while doing so. Make that considerably more times than just a few, and when that rear goes, it just wants to keep sliding sideways forever. Well, unless you have studs in the tire, then we are talking bike behavior that is more controllable and normal, including throttle on weight shifts, which a rider uses for various reasons.

[nrp]

Carl T - Gotta study your post & video, & think some more. I'll be gone for a few days. Your point about the effects of road roughness may be important.

 

Otherwise I don't think the lateral capability of a tire depends on the size per se of the tire contact patch, just the normal (perpendicular) force. Of course the tire patch size is also related to the vertical force and goes inversely as the contained air pressure.

THX,

NRP

[Heli]

Well, what an interesting thread! We have an excellent course over here, run by Honda Australia, which gives advanced riding instruction at our State Motorcycle Track. HART teach to shift weight across the saddle into corners, and much of what has been discussed here, eg look well ahead, etc:

 

 

 

 

The initial thread topic, about leaning better one way than the other, interests me: I thought I was evenly balanced, but after a heavy run through some of our ski field roads (following Ducatis, Agustas, etc!) I've shot my front tyre after only 8000km, and there is definitely an indication of more wear on the left than the right:

 

 

 

I'm going to have a good think about this tomorrow, and sort myself out!

[zbassman]

This has been an interesting thread. I thought I'd give you all a follow-up from my original post.

 

I've been really paying attention to how I turn to the left and right to try to pinpoint what is causing me to feel less sure of myself in right handers. I've noticed a few things. And I've tried a few things different.

 

As far as adding throttle during a turn, I've always gently rolled on throttle during turns. But given some of the discussion here I tried it with a steady throttle for awhile. What I've found is that if I've approached the turn well, anticipated the degree of the curve correctly and set the appropriate amount of lean then a steady throttle feels pretty solid. However, if I get in to a turn too early or the curve is more acute than I anticipated and I need to lean in a bit more then a steady throttle feels less secure and a bit of roll on helps me feel that the bike is more steady.

 

I'm no rocket scientist, don't play one on t.v. and won't even pretend to understand the physics involved with turning a motorcycle. From reading various posts here I know there are people way smarter than me hanging around. I'll leave the discussion of gyroscopic forces, intertia, centripetal force, etc. to those of you who are rocket scientests But what I do know is adding a little throttle feels better to me. Even if that's purely psychosomatic it doesn't hurt so I'll stick with it.

 

Another thing I've noticed is my body position. For whatever reason I find that as I start a right hand turn or lean I tend to lean my body to the left while trying to lean the bike to the right.

 

Going to the left I am really leaning my body left, even sort of shifting my weight to my left hip, leaning my right leg into the bike, and "kissing the mirror". But to the right I sort of lean my head to the right a bit, but almost pull my torso to the left. It must look very odd from behind. So, I've tried to be much more cognizant of getting my whole body in to the righties. Making sure I shift my weight to my right hip, kiss that right mirror, and lean my left leg in to the bike. Its almost an exaggerated effort in that I am sure I am often putting more in to my body english than the turn requires. But it seems to be helping. I am feeling more comfortable to the right. Not comfortable yet, but better.

 

Thanks for all the ideas, thoughts, and great discussions.

[nrp]

Zbassman - Do you have similar vision in each eye? Or an injury etc that makes turning your head harder one way?

 

Another insight is that a M/C engine flywheel that turns CCW when facing the rear (i. e. chain drive), or CCW when facing the left side of a bike (i. e. shaft drive), will cause a small amount of pitch forward in right hand turns, or pitch rearwards in LH turns. That same CCW rotation-viewed-from-the-left side lateral crankshaft engine will want to yaw to the left upon RH roll initiation and yaw right when rolled the opposite way. This is due to gyroscopic effects. In general I would expect these effects to be quite minor though to the point of being transparent to the average rider.

 

The same longitudinal crankshaft engine bike doesn't have any roll/yaw coupling, but does have the yaw/pitch coupling noted earlier.

 

I can understand the acceleration feel-goodies in a turn but as you may have noticed, I was wondering why. So far I have 1) to take up drive line snatch, and 2) maybe a benefit for unexpected road roughness. Otherwise the topic is still open for discussions.

[Huzband]

If you have doubts about trusting the tires, just gaze upon this for a few moments.

 

 

 

 

I especially like the sparks from the exploding FD.

 

Which, BTW, is on the wrong side of the bike.

 

 

I actually have some positive comments to add, but that will have to wait till tomorrow.

[Heli]

I actually have some positive comments to add, but that will have to wait till tomorrow.

 

Waiting, waiting

[zbassman]

Zbassman - Do you have similar vision in each eye? Or an injury etc that makes turning your head harder one way?

...<snip>...

 

My vision is pretty much the same in both eyes, the right is a little weaker. But that got me thinking. I do have some hearing loss in my right ear (too many nights spend standing to the left side of too many drummers with that snare beating in my ear). I wonder if that's what is making me feel unsure about the righties...