Observations about aggressive body position

[adouglas]

I've been thinking recently about how the bike feels when I make the effort to take a more aggressive riding position while cornering.

Take a look at the pic below: Marc Marquez leading Jorge Lorenzo as they drive hard out of a corner.

Notice how these guys are so low down and to the inside that their right hands are actually to the left of their chins. Left forearms are in full contact with the tank. Eyes are looking ahead at the turn exit.

This is way more extreme than you'd ever need to be on the street, but... I've noticed that the more I get my head down and to the inside, with my outside arm on the tank, the more stable the bike feels while driving out of the corner. It's as if locking into the bike like that gives me the confidence to drive harder.

Sometimes it feels like I'm doing what's shown in the pic but I know that in reality I'm nowhere close.

Have you fooled around with this? What's your experience been?

[csmith12]

Yea, what the pic shows is called "the pick up". Stay leaned off, pick the bike up and roll harder/pin it. It works wonders for your lap time (nearly a full second off). And... it's fun.

[Motofool]

Originally Posted by csmith12

Yea, what the pic shows is called "the pick up". Stay leaned off, pick the bike up and roll harder/pin it. It works wonders for your lap time (nearly a full second off). And... it's fun.

That reduces the angular inertia for the bike to be straighten up.
Basically, the combined CG is still at certain lean angle respect to the vertical, but the suspension is working at a more favorable angle for the brutal acceleration.

For street riding within legal speeds, I don't see the need for such dramatic postures, ............but I am old and slow ...............

[BRad704]

Edit: Just realized I had forgotten this tab, and missed a few responses. LOL.


My original post:
Very limited experience here... But I agree. I think it has to do with changing your center of gravity.

When you are sitting in line with the center line of the bike/seat/bars, your body is being pushed toward the outside of the corner, causing rotational forces on the bike because you have to hang on.

When your body is off the inside, you are bringing your own personal CG closer to the bike, and closer to the pivot point of that outward rotation.

Basically, there is less inertia of your own body trying to disrupt the bike.

This is all speculative, but makes sense in my head. And it's worth what you paid for it.

[choneofakind]

My experience: you'll feel like you look like those guys, but you'll never be anywhere close. Even if your outside arm is on the tank and your chin bar is almost on your inside hand, check the butt-cam and you'll be amazed how much further (and faster) you can really go.

[adouglas]

Originally Posted by BRad704

Edit: Just realized I had forgotten this tab, and missed a few responses. LOL.


My original post:
Very limited experience here... But I agree. I think it has to do with changing your center of gravity.

When you are sitting in line with the center line of the bike/seat/bars, your body is being pushed toward the outside of the corner, causing rotational forces on the bike because you have to hang on.

When your body is off the inside, you are bringing your own personal CG closer to the bike, and closer to the pivot point of that outward rotation.

Basically, there is less inertia of your own body trying to disrupt the bike.

This is all speculative, but makes sense in my head. And it's worth what you paid for it.

If the bike didn't lean I'd buy it.

But since the bike is leaning, the resultant force vector is at a diagonal, connecting the contact patch with the CG.

As a high school science teach I once had liked to say, "look at da vectors!!!!"

[Motofool]

Originally Posted by adouglas

But since the bike is leaning, the resultant force vector is at a diagonal, connecting the contact patch with the CG......

Yes both bikes are still turning, but they are in the process of "picking the bikes up" or coming out of the lean as they drive hard out of a corner and into a straight or the next turn in opposite direction.

Why do they conserve the extreme hang-off posture when they are not at maximum lean / minimum radius for that turn?

[Panda]

I think Hernan has it right. Leaning off the bike increases the effective lean angle. The effective lean angle being the physical lean angle of the bike combined with the CG offset created by leaning off or by improper body positioning.

EDIT: Link - http://www.howfastcanigo.com/howitworks.html

[lgk]

Originally Posted by choneofakind

My experience: you'll feel like you look like those guys, but you'll never be anywhere close. Even if your outside arm is on the tank and your chin bar is almost on your inside hand, check the butt-cam and you'll be amazed how much further (and faster) you can really go.

what your brain thinks is happening, sometimes is no indication of reality.

happened to me while i was taking ballroom dancing class.
i was thought i was cool until i saw the video, looked like a hungry zombie lunging into a group of tasty people.

[alex.s]

habbits are hard to break. this is how i ride on the street. the other day i accidentally turned my bike off with my chin.

[adouglas]

Originally Posted by lgk

what your brain thinks is happening, sometimes is no indication of reality.

happened to me while i was taking ballroom dancing class.
i was thought i was cool until i saw the video, looked like a hungry zombie lunging into a group of tasty people.

You should post that video.

BRAINZZZ!!!!!!!

[adouglas]

Originally Posted by alex.s

habbits are hard to break. this is how i ride on the street. the other day i accidentally turned my bike off with my chin.

Bahahahaa....

Is that why you rate bikes on how well they crash???

[alex.s]

crashing is a normal part of life... people are just in denial about that.

[alex.s]

Originally Posted by adouglas

If the bike didn't lean I'd buy it.

But since the bike is leaning, the resultant force vector is at a diagonal, connecting the contact patch with the CG.

As a high school science teach I once had liked to say, "look at da vectors!!!!"

/cry what if i only have quaternions!!!!

[csmith12]

Originally Posted by adouglas

As a high school science teach I once had liked to say, "look at da vectors!!!!"

Hold up, sorry to derail your thread but your a science teacher? This is what I want to do what I grow up. Can you pm me your thoughts on that and possibly teach science at the high school level?

School me up for what I am in for please.

/back to your regular scheduled thread.....

[Motofool]

Originally Posted by Panda

...........Leaning off the bike increases the effective lean angle. The effective lean angle being the physical lean angle of the bike combined with the CG offset created by leaning off or by improper body positioning.

EDIT: Link - http://www.howfastcanigo.com/howitworks.html

Good link, Dan; thanks !!!

Some thoughts on motorcycle stability

[tfkrocks]

Originally Posted by csmith12

Hold up, sorry to derail your thread but your a science teacher? This is what I want to do what I grow up. Can you pm me your thoughts on that and possibly teach science at the high school level?

School me up for what I am in for please.

/back to your regular scheduled thread.....

He was talking about a science teacher he previously had

[adouglas]

Originally Posted by csmith12

Hold up, sorry to derail your thread but your a science teacher? This is what I want to do what I grow up. Can you pm me your thoughts on that and possibly teach science at the high school level?

School me up for what I am in for please.

/back to your regular scheduled thread.....

Sorry, a typo... should have said "as a high school science teacher I once had...."

I'm not an expert in anything but writing (my career), but I have been known to play one on TV....

[raphaeltube]

Hi

There is another factor which is very important in pro racing, but which is of absolutely no consequence to daily street riding, and that is conserving the sides of the tyres.
As I'm sure you've all noticed, our (commuting street riders) rear tyres end up wearing flat in the middle. The opposite is true for track racers. The edges of their tyres are made from very soft compound to be sticky enough to deal with extreme cornering. But this also means they wear out fast, and will need to be changed in a pit stop.
The riders keep their cornering position longer than necessary while exiting a corner as a meant of getting the bike upright as soon as possible, and back onto the centre of the true, so conserving the precious edge rubber.

But sure leaning in corners gives stability and control.

-R

[ally99]

I noticed a major difference as I got lower in my position at the track. Granted I was never gonna drag elbow or anything that low, but the lower I got my head, the happier the bike felt. I used that lowering of the body to tighten up mid-corner. Keith Code calls is the hook turn. Fun as HELL!
Edit: I did notice after riding the GSXR 600 at the track for a while just how much easier it was to get my head lower b/c my arms were out of the way. My stock bars on the 250 make it so that my wrist gets in my way and I don't get quite as low as I did on the GSXR. So I've gotta keep practicing!

[RedOctober]

Originally Posted by raphaeltube

Hi
The riders keep their cornering position longer than necessary while exiting a corner as a meant of getting the bike upright as soon as possible, and back onto the centre of the true, so conserving the precious edge rubber.

But sure leaning in corners gives stability and control.

-R

Close...but not quite. Contact patch of the tire, when leaned over, is smaller than when standing up straight, with the maximum patch being while at 0 deg lean. The point of "pickup" is to stand the bike up faster because the faster you do it the faster you can roll on throttle. At 60 deg lean the patch is only able to support X power delivered to the rear wheel, and at 30 deg lean you can do max of Y power, where X<Y. If you attempt Y power at max lean your rear will slip and you'll highside. Thats why people highside...the rear traction breaks.

If you were to do a lazy 5s roll on from apex of corner to exit, you wouldn't need to care about pickups. But these guys are trying to go from 0 throttle to open in 2 seconds or as fast as they can feel they can.

[Misti]

Originally Posted by csmith12

Yea, what the pic shows is called "the pick up". Stay leaned off, pick the bike up and roll harder/pin it. It works wonders for your lap time (nearly a full second off). And... it's fun.

Exactly, it's all about getting the bike picked back up as soon as possible so you can roll on the gas harder at the exit of the corner. If you try to roll on the gas hard while the bike is still way leaned over you seriously risk sliding the rear...

Originally Posted by ally99

I noticed a major difference as I got lower in my position at the track. Granted I was never gonna drag elbow or anything that low, but the lower I got my head, the happier the bike felt. I used that lowering of the body to tighten up mid-corner. Keith Code calls is the hook turn. Fun as HELL!
Edit: I did notice after riding the GSXR 600 at the track for a while just how much easier it was to get my head lower b/c my arms were out of the way. My stock bars on the 250 make it so that my wrist gets in my way and I don't get quite as low as I did on the GSXR. So I've gotta keep practicing!

Nice! Yes, Keith Code calls the process of lowering your upper body down and forward the "hook turn". It's good form in general to be over to the inside of the bike down a little bit but there is a real specific thing that happens when you drop your upper body farther down and farther forward while cornering.... what do you think this would do to your line? What situations might this technique help with?

Misti

[adouglas]

Originally Posted by Misti

what do you think this would do to your line? What situations might this technique help with?

Misti

Empirically I'd say it tightens the line, because when I get way down (chest actually in contact with the inside edge of the tank) the bike seems to "want" to turn. I'm thinking that's really just me perceiving it as being more stable. For sure it feels more solid and confidence-inspiring.

Now… why? Not sure. Maybe it's because I'm reducing the moment arm so the bike can rotate around the longitudinal axis more easily. Maybe it's because I'm locating my body more positively, locking it onto the bike so I'm not unconsciously fighting it. Maybe it's both, or something else.

What situations… I'm thinking in too fast and/or decreasing radius. Any situation where you need to tighten your line.

I really need to get to the track. It's almost impossible to find a corner near me where I can experiment with this stuff. Seems there's always a car right in front of me, forcing me to go around the corner as if I were on a Vespa.

[Misti]

Originally Posted by adouglas

Empirically I'd say it tightens the line, because when I get way down (chest actually in contact with the inside edge of the tank) the bike seems to "want" to turn. I'm thinking that's really just me perceiving it as being more stable. For sure it feels more solid and confidence-inspiring.

Now… why? Not sure. Maybe it's because I'm reducing the moment arm so the bike can rotate around the longitudinal axis more easily. Maybe it's because I'm locating my body more positively, locking it onto the bike so I'm not unconsciously fighting it. Maybe it's both, or something else.

What situations… I'm thinking in too fast and/or decreasing radius. Any situation where you need to tighten your line.

I really need to get to the track. It's almost impossible to find a corner near me where I can experiment with this stuff. Seems there's always a car right in front of me, forcing me to go around the corner as if I were on a Vespa.

Right, it tightens the line, hence the name "hook turn." what happens is that when you get your body down and forward the bike kind of hooks in and pulls a tighter line. The benefits of this technique is that you can tighten your line WITHOUT adding lean angle. this is a HUGE benefit if you find yourself running a little wide but are already at maxed lean angle.

In too fast or decreasing radius turns are excellent situations to use the hook turn.

Now, how does it work? Why would the line tighten (without adding lean angle) when your move your body forward and down?

Misti

[alex.s]

when the weight is higher up on the bike, centrifugal force pulls it, but point of rotation is the axis formed between the two contact patches, so due to the lever action, the same amount of centrifugal force placed further from the pivot point (the tires) provides higher rotational torque, meaning the front tire has to be straighter than it would if the weight was lower.... straighter tire, straighter turn.... think about when actually turning the bike... the bike doesn't TURN until you stop changing angle. then the tire goes from counter-steering into positive-steering around the turn. lower weight, less rotation torque from centrifugal force, more effective turn.

[tooblekain]

Originally Posted by Misti

Now, how does it work? Why would the line tighten (without adding lean angle) when your move your body forward and down?

Misti

Here's my thoughts on why it works. Most of your body mass/weight is your upper body. When you bring your upper body forward and down, you are essentially putting more weight on the front end. When you put more weight on the front end, it compresses the forks. It's very similar to trailbraking in the sense that you're not using the brakes.

I was actually using this hook turn technique this weekend at Chuckwalla. I was able to get a PR of 2:08.41 and a few 2:08s and averaging lap times of 2:10s. I was able to do this by not using the brakes anywhere on the track since the 250 you need to preserve your momentum.

While Yamaha School of Champions emphasizes using the brakes to help turn the bike, I find it kind of detrimental to a 250 because you need to be pretty much pinned as much as possible. On the 250, my mantra is any time you use the brakes to shave off a fraction of a second, it takes seconds to regain the forward momentum you had.

[alex.s]

Originally Posted by tooblekain

2:10s. I was able to do this by not using the brakes anywhere on the track

wat?

not even turn 1? turn 9?

[adouglas]

I'm with Tooblekain on this one. Assuming steady-state acceleration (i.e. the suspension is settled... no dynamic weight shift front-to-rear) and lean (the bike is already turning/tracking, no additional steering input) then shifting weight forward will compress the forks a bit and therefore alter geometry slightly.

[tooblekain]

Originally Posted by alex.s

wat?

not even turn 1? turn 9?

That's right. NO BRAKES anywhere. I'll have to post video.

As for turn 1, my thought process is that it doesn't exist.

[alex.s]

this is clockwise? what are you doing going into turn 8? just engine brake? where are you off the throttle?

[Panda]

Originally Posted by adouglas

I'm with Tooblekain on this one. Assuming steady-state acceleration (i.e. the suspension is settled... no dynamic weight shift front-to-rear) and lean (the bike is already turning/tracking, no additional steering input) then shifting weight forward will compress the forks a bit and therefore alter geometry slightly.

Why does it have to be steady state acceleration? Shifting weight forward alters steering geometry and makes the bike easier to turn.

[adouglas]

Meaning that the effect of body weight shifting slightly would be utterly wiped out by, say, braking or heavy acceleration. It'd have to be steady-state for any effect to become evident, assuming it was ONLY due to rider weight shift (as opposed to, say, putting additional pressure on the bars due to moving your body... i.e. unconscious steering input).

The difference in c.g. location from normal sportbike "upright" and low-and inside can't be that much. Certainly not nearly as much as you'd get through braking or acceleration.

I believe Code wrote that the weight shift to the front under hard braking is something like 150 lbs.

BTW, when are you going to tell us about the TRC?

[tooblekain]

Originally Posted by alex.s

this is clockwise? what are you doing going into turn 8? just engine brake? where are you off the throttle?

Yes, clockwise. For Turn 8, just down shift after the 1 marker and at the beginning of the candy stripes on the left. Since Turn 8 is uphill and combined by the back torque of the engine due to the downshift, it's naturally slowing me down going through there. However I am carrying a lot of corner speed at 9 that I am dragging knee and toe. The corner worker that was working that corner said my corner speed through the 8-9-10 complex was ridiculous.

I'll have to see if I have any video footage of the passes I did in 8-9-10. I know a lot of them were between 9-10 and I would be out of 10 before the other rider, but get out motored on the back straight but I retake at Turn 11

[Panda]

I don't think the CG changes appreciably under acceleration unless the riders body is getting thrown backward or forward. I don't believe weight transfer caused by acceleration impacts CG.

I actually didn't do TRC - I figured I was trying to smash too many events into too little time. I did, however, make it to the track on Monday.

[adouglas]

In TOTW 2 Code writes that a mild acceleration produces the ideal weight balance… 60% rear, 40% front. If bike plus rider (plus gear) clocks in at 600 lbs. that means the rear is carrying 120 lbs more than the front, compared to zero acceleration.

Assuming I'm thinking about this clearly, which is far from certain.

[Misti]

Originally Posted by tooblekain

Here's my thoughts on why it works. Most of your body mass/weight is your upper body. When you bring your upper body forward and down, you are essentially putting more weight on the front end. When you put more weight on the front end, it compresses the forks. It's very similar to trailbraking in the sense that you're not using the brakes.

I was actually using this hook turn technique this weekend at Chuckwalla. I was able to get a PR of 2:08.41 and a few 2:08s and averaging lap times of 2:10s. I was able to do this by not using the brakes anywhere on the track since the 250 you need to preserve your momentum.

While Yamaha School of Champions emphasizes using the brakes to help turn the bike, I find it kind of detrimental to a 250 because you need to be pretty much pinned as much as possible. On the 250, my mantra is any time you use the brakes to shave off a fraction of a second, it takes seconds to regain the forward momentum you had.

Exactly, well explained.

Originally Posted by tooblekain

That's right. NO BRAKES anywhere. I'll have to post video.

As for turn 1, my thought process is that it doesn't exist.

The first exercise of the day at CSS is always 4th gear NO brakes. What do you think this would help with?

[adouglas]

Originally Posted by Misti

Exactly, well explained.



The first exercise of the day at CSS is always 4th gear NO brakes. What do you think this would help with?

Learning how to avoid charging the corner. Learning how to keep your average speed up. Learning that the chassis should be settled as early as possible so you can get on the gas sooner -- and therefore carry more speed out of the corner.

I prefer to ride in a manner that doesn't rely on heavy braking for much the same reasons that tooblekain cited. I've always been a fan of small, light, low-power vehicles that rely on momentum (I drive a Honda Fit).

What opened my eyes to just how big a deal momentum can be was driving on the track; years a go I did a season or two of time trials, mostly in old, very underpowered Saabs (if you're a geezer like me you might remember the Saab Sonnett). Those cars were a lot like the Ninjette. Very agile but little power. I could easily keep up with Vettes and Vipers in the corners but as soon as the road straightened… forget it. In a vehicle like that a loss of momentum COSTS so you learn how to use the brakes less.

My 750 is far and away the most powerful machine I've ever owned/operated of any kind… but a lifetime of habit is hard to break.

[Panda]

Can you lose the rear under braking in a turn? It seems like you'd lose the front before you'd lose the rear?

I'm also wondering if getting all your braking done first is the fastest way around a corner as taught by TOWTII. Why do MotoGP, WSBK, etc. use trail braking during FP and qualifying?

[Falcor]

I think it depends which brake you use, but the bike will stand itself up if you brake in a turn too hard. Braking should be done before entering a turn.

[csmith12]

Originally Posted by Panda

Can you lose the rear under braking in a turn? It seems like you'd lose the front before you'd lose the rear?

Yes, just like overloading the front tires traction with too much weight with braking, you can underweight the rear to initiate traction loss.

The intent of trail braking isn't really to scrub off large amounts of speed. Take this hypothetical example;
A right turn & rider with a an entry speed goal of 50mph and the bike is traveling at 100mph;
Before the turn in point, scrub off 45ish mph via heavy straight up braking from your brake marker
Just before the turn in point, begin gently, progressively and smoothly easing off the brake and continue to decel until you reach the goal speed of 50mph, then begin throttle roll.

In this example; per throttle control rule #1 and since the rider is still on the brakes, the rider is underweighting the rear tire from the turn in point until the bike reaches 50mph. This is the time where that bike/rider/tire combo runs the highest risk of rear tire traction loss.

What should the rider do in order to stabilize the rear tire under these conditions?