So who's got their knee down?

[Two Smoker]

Yea i hit my knee on a cats eye just yesterday, luckily though i was only doing about 60 kmh (around a 25 corner) so it didnt hurt.....CK i wish my bike could do 190-200 because i can only get 170 on the front straight and hold it through Jennian

[Kwaka-Kid]

I don't see how going around slow corners can achieve knee down unless you are hanging off the bike to buggery? As the slower the corner the less the lean anyway as you are carrying less speed?

Now dont call me physics boy or anything dude, but actually it doesnt make sod all difference? this would only imply you dont push your low speed corners fast enough and carry the speed through them, right? because so long as you enter the corner rather fast and HAVE to push the bike so low that you scrape your knee just to make the corner then your going to have a fair bit of force, just that at low speed everything happens faster if you ask me, i really dont mean to sit here and show off but at taupo i touched my left knee once going around the hairpin, although i cant say how fast that is exactly i know its slow but i had to do it to make the corner (maybe not quite HAD to touch the knee but i was stickin it out there and it did) and what i notice is at lower speed everything wobbles and the bike just about falls over and is like teatering on the edge of falling and going up, and its ALOT harder to balance there, but shit i still carried some good speed for the given corner and as i said tapped the knee and the left peg, i compare this with the left b4 it where you are doing a guestimated 80-100? and its so easy and the bikes movement is very predictable and slow, i think its mainly too because of the gyro forces etc it takes alot more effort to push hte bars anywhere so slows down any "tweaky" movements(e.g that slow hairpin you slightly counter-steer etc and makes a diff wayyyy too easy). Alright ill admit now ive forgotten where i was going with this i guess i was just trying to throw an example of a few experiences ive had, that example is comparable to Pukekohes Castrol corner where its piss easy to gentally and progressivly push the bike lower as you go faster just to make the corner perfect and touch your knee/pegs, and the hairpin takes more concentration because of the slow speed but still, can be done if you enter it fast enough that you must push the bike lower to achieve the task of making the corner whoa, sorry guys i just came home from work and being in the heat wearing wet-weather gear, dont think anything ive said makes sense but im sure some examples could be related to and thought about.

[Coldkiwi]

oh damn.. I'm starting to agree with KK

that cannot be good!

[Big Dog]

In books/mags offering instruction in the "art" they reccomend practicingat round abouts at 25-30 kmph to hone your skills before attempting it at higher speeds as even a small ripple in the road can send the unprepared into a full on slapper if your "throttle balance" (the area between acceleration and deceleration is not out side the boundaries of your available grip) is not right.

Note: you need to be accelerating to be stable that far over, otherwise you have none of your grip matrix availible if you need to change direction or speed.

KK, the young are so rash
In the absence of perpetual mothion, every thing is acc or decelerating.

All I said was it is easier to stiy inside your grip matrix if you are accelerating if you need to take emergency action.
Read posts before you criticise them.

It is easier to get it down when decelerating given the bikes increased tendanct to tip. it is safer (and wears down your chicken strips faster) if you accelerate).

Your call KK as we don't all get staff discounts on medical treatment

[Kwaka-Kid]

oh okay? well i dont understand all this flash yabba! but sorry dude i didnt mean to fully flame your post or nothing, and im not up to speed with all the text book stuff but i did see the matrix, and yeah i got a good grip on what was going on i think, some chick with tight leather and guns runs around trying to keep all the dudes turned on or something right? but yeah i was just talking seat of the pants what i thought was going on and how i felt etc, but cheers and sorry once again if u thought i said it like nasty, heheh and yeah i prolly do need to read into posts more and try to understand them

[wkid_one]

[QUOTE=Kwaka-Kid]Now dont call me physics boy or anything dude, but actually it doesnt make sod all difference? this would only imply you dont push your low speed corners fast enough and carry the speed through them, right? [QUOTE]

Are you saying the speed you travel as no bearing on how far you lean your bike???

My point is thus - the slower you are going the further you have to hang off your bike to drag your knee. By sheer nature of a bikes physics - a bike becomes less and less stable the further it is lent over as the speed decreases - it is the gyroscopic forces at work as there is reduced gryoscopic forces to get the bike upright and the front wheel wishes to tuck instead. Therefore - the slower your speed, the more difficult it is to NATURALLY get your knee down. Physics is against your here KK....a slow bike wants to either stay upright or fall over. Dragging knees around a slow corner is not a life prolonging activity. This is as CK referring to it being easier to drag a knee at higher speeds - why? Because bikes are more stable lent over at higher speeds. I refer to slow speed - NOT SLOW MARKED CORNERS. Hell the first corner I got my knee down on was the Hairpin at Puke....

But the most enjoyable are the corners that go on forever with your knee on the ground as you pick up speed. The 45kph LHer after the entrance to Kaitoke Kart Track is a good example of this, as is the north bound onramp at Newlands.

Hanging off the bike serves one main purpose and that is to shift your COG closer to the inside of the corner and therefore allow you to corner faster by sheer virtue of the fact the bike remains more upright throughout the corner than it would ordinarily without shifting your weight.

Rather than 'hanging off the bike' - try cornering like this. When you come to a corner, weight your outside foot peg, and pivot your hips around the tank so the inside hip comes as close as possible to the bars and drop your inside shoulder. This weight shift alone is better than hanging off the bike - your corner speed will increase and you will find you will naturally slide your knee eventually.

[Coldkiwi]

not sure if I fully follow/agree with your gyroscopic forces explanation wkid (I'll have to read it again when i have more time) but I do agree with the pivoting method. Only flaw in it is when you can't lean any further because your thigh/slider is between the road and fairing. Of course... that may not be such a bad place to stop leaning over further!!

[Kwaka-Kid]

wkid i hear you, and althought what you said i think is true, when you are going faster, there is more centrafugal force acting on your bike towards the outta of the corner i.e putting more sideways pressure on your tyres right? so if you got shit tyres like i always do you drift at high speed, and low speed is better because there is less-you jsut have to learn how to be stable smooth and balance better. right? maybe not sounds right to me and it feels right, just take care on the slow ones be smooth and balanced and youll be right.

[Posh Tourer :P]

wkid i hear you, and althought what you said i think is true, when you are going faster, there is more centrafugal force acting on your bike towards the outta of the corner i.e putting more sideways pressure on your tyres right? so if you got shit tyres like i always do you drift at high speed, and low speed is better because there is less-you jsut have to learn how to be stable smooth and balance better. right? maybe not sounds right to me and it feels right, just take care on the slow ones be smooth and balanced and youll be right.

You'd be surprised by how much centrifugal forces matter... have you ever ridden anything with solid wheels ie no spokes? Very difficult to turn/change direction. That particular situation doesnt apply to cornering, but shows how much centrifugal force can do to change handling

[pete376403]

You'd be surprised by how much centrifugal forces matter... have you ever ridden anything with solid wheels ie no spokes? Very difficult to turn/change direction. That particular situation doesnt apply to cornering, but shows how much centrifugal force can do to change handling

That was the logic behind 16" front wheels back in the '80s. It was likened to power steering. Unfortunately the factories just basically stuck 16' wheels and longer forks on bikes that had dubious handling with 19" fronts, so all they did was make the handling even more dodgy than it was before

[Kwaka-Kid]

hmm interesting and yeah, +force on the actual bikes weight etc going around hte corner, i.e me going around a corner on 260kg GS1000 then trying on 150kg race VFR400, difference is amazing in how much more speed you can take, hence why those damn little 250's etc can hold such high corner speed, for if you run the same rubber compound as a big bike, the big bike slides like with less speed around hte same corner then a light bike would, does anybody know a guestimate on the % of speed difference/force difference per kg or something? interesting.

[pete376403]

Dr Gordon Blair of Queens University, Belfast did a study back in the '70s to find the optimum engine size for racing. Looked at weight, fuel consuption, power, rider fatigue, power, tire wear, all sorts of things. He found the ideal size was a 300. This was in the era when 54 HP Yahama TZ350s were winning everything while competing against 750s from everyone else. The TZs were so successful that the open class was restricted to over 350s. Didn't stop them though, they just bored the motors out to 354 and won anyway

[Two Smoker]

Yep my Uncle Jim (Who's 70 years old) still races them now , he said his is pumping out about 70 hp and is good for 240 kmh (At 70 i reakon thats fucking legend....) Ill see if hes going to Puke on the 23rd......

[wkid_one]

Try this explanation then CK

Why is it harder to balance on a stationary motorbike compared to a moving one? Is it a gyroscopic effect on the wheels?

As you suspect, gyroscopic effects do play a role. Because it has only two wheels, a motorbike is inherently unstable. When it's stationary, it is only in equilibrium--that is it experiences no net force or torque--when it's perfectly upright. The slightest tip causes it to fall over. You must be very careful and agile to keep it balanced. A physicist would say that the motorbike is statically unstable or that it has an unstable static equilibrium.

For the motorbike to remain upright, you must keep the overall center of gravity (yours and the motorbike's) directly above the wheels (actually the line formed by their contact points on the ground). That's very hard to do when the motorbike is stationary. But when the motorbike is heading forward, it naturally steers itself under the center of gravity. If the motorbike begins to tip to one side, its front wheel automatically steers in the direction of the tip and the forward moving motorbike soon drives its wheels back under the center of gravity. This automatic steering is due to both gyroscopic precession in its spinning front wheel and to the shape and angle of the front wheel fork. If you hold the motorbike (or a bicycle) off the ground, spin its front wheel the right direction, and then tip the motorbike, you'll see its wheel turn toward the direction of the tip because of gyroscopic precession. If you return the motorbike to the ground and then tip it to one side, you'll see that its wheel will automatically turn toward that side because of the fork shape.

With both effects helping the motorbike steer under the center of gravity, the moving motorbike is very stable. A physicist would say that it is dynamically stable. Everything I've said also applies to bicycles and was pointed out by British physicist David Jones in 1970. Bicycles are so dynamically stable that almost anyone can ride them without hands and not tip over!

If you apply the brakes while making, say, a left turn on a motorcycle, the motorcycle will tend to "stand up." That is, it will tend to fight the lean you make into the turn. Why?

When you turn left, you are accelerating toward the left and your velocity is changing toward the left. This leftward acceleration requires a leftward force and that force is supplied by friction between the ground and the motorcycle's wheels--the ground pushes the wheels toward the left. However, this leftward force on the wheels also exerts a torque (a twist) on the motorcycle about it's own natural point of rotation--its center of mass. As the ground pushes the wheels toward the left, the motorcycle tends to begin rotating. In this rotation, the wheels begin moving toward the left and the driver's head begins moving toward the right--the motorcycle "stands up"! Actually, if you lean far enough to the left as you turn, an opposing torque due to the upward force that the road exerts on the wheels will balance the first torque and your motorcycle will experience no net torque--it won't stand up at all. On a high-speed turn, you must lean quite a bit to avoid the "standing up" problem, which is why motorcycle racers practically touch the ground as they turn.

[Big Dog]

but sorry dude i didnt mean to fully flame your post or nothing,

and I was not torching you merely having a laught at your expense