Jump to content

Recommended Posts

riding on the mountains i dont know how much i lean, or what is the max lean.  i know on a sport bike 55 degree is the max, but how do i know what does a 55 degree lean feels like? the new dunlop q4 able to lean 62 degree, even more scary to test it out.  i drag my knee before.  i been playing Ride 2,3 ,moto gp 17 and notice at 52 degree the rider is dragging knee, so it means your knee is an indicator how far you lean, a general guide, but can it tell you your max lean? no right.  what if you stick out your toe more, so when it hits the ground you know for sure you reach the max lean fore your tires.

  Wish there is a motorcycle stand to attach to you bike and just lean to the max and get use to what does it feels like, so next time you dont have to worry about not leaning enough so you can focus on gas.

Share this post


Link to post
Share on other sites

Developing a feeling with the tire is half the battle of any motorcycle racer and it is one of the hardest skills to learn. A lot of tire and frame research efforts go into delivering good signals to the rider. If you drive any go-kart at racing pace you already know. In most corners you want to ride as fast as you can without sliding so you become very aware of how the tires are reacting.

The knee is a reference gauge for any racer but like you say it doesn't mean it solves all problems. Max lean angle is a function of speed, tire technology, temperature, weight distribution and I am sure many other factors.

Share this post


Link to post
Share on other sites

Spaghetti has given good info above, and I will add that a good way to get experience with using more lean is to get a small bike (50cc, or 150cc, for example) that you can take to a go-kart track. Easier to get your knee down, safer environment, and you can lean way over at much lower speeds to get "used to what it feels like" and develop a sense of traction and feeling the feedback from the tires.

  • Like 1
  • Thanks 1

Share this post


Link to post
Share on other sites

While riding on the mountains you should not be pushing your tires to the limit; that just means excess of danger with little reward or improvement of skills.  Please, note that I mention the limit of physical pavement-rubber traction and not lean angle of the chassis.

Lean angle is a natural consequence of the centripetal forces of turning and it mainly depends on the square of the speed of the bike and on the inverse of the radius of the turn: meaning in simpler terms that double the entry speed (but same radius) puts four times more lateral stress on the contact patches of the tires and that half the radius of turn (but same speed) puts double stress on those patches.  The manufacturer of your sport bike tries to provide a lean clearance that matches the maximum traction capability of your tires in good pavement conditions.

The resulting angle of lean must be there to compensate for those cornering lateral forces in such a way that the bike keeps its lateral balance (not crashing over towards the outside of the turn).  What is happening at the same time?  Both tires "feel" an increased weight of your body and the bike, as much as double (2g) around 60-degree lean; hence their sections become less pliable and have to work harder to keep grip.  The suspension is now compressed by the added weight and its work to follow the surface and keep the rubber in contact with it is more difficult because the direction of the strokes is inclined while the irregularities of the track keep pushing it vertically.  

All the above works as described if, and only if, you have the luxury of clean dry pavement.  Otherwise, your tires will have less capacity to resist the action of those lateral forces (assuming good conditions of tires, inflation and suspension, as well as good riding techniques and per-tire-weight distribution).  How much less traction will you have?  That is something impossible to predict on public roads, where you could suddenly find spills of oil, Diesel, anti-freezing coolant, or sand or street markings or steel manholes or animal carcasses.

If you ride on the edge of available traction, you will not have available traction to use in the event of an emergency or evasive maneuver, like braking or swerving.  You always choose entry speed to negotiate certain radius of a fixed corner, lean angle follows that decision adjusting itself to keep balance, and both tires and suspensions are loaded with extra forces, which should never grow beyond the limits of traction for the specific conditions of the road.  

Please, read some more about this:

https://www.motorcyclistonline.com/riding-tips-traction-science-tires-keith-code-break

https://www.motorcyclistonline.com/blogs/tread-envy-code-break

https://www.motorcyclistonline.com/blogs/dragging-your-knees-code-break

https://www.motorcyclistonline.com/leaning-bike-code-break

http://forums.superbikeschool.com/topic/3331-have-you-ever-slid-the-front-without/

 

26BFF8ED-F90C-4CDE-9CB8-FF1855A2B8FC.jpeg

  • Like 1
  • Thanks 1

Share this post


Link to post
Share on other sites

Regarding the graphic of lean angle and G-force above: that would only hold true if the motorcycle had a theoretical "zero width tire". The apparent lean angle and the effective lean angle are different on a motorcycle due to the contact patch being off to the side versus straight down the center line of the motorcycle. For example a MotoGP bike at 62 degrees of lean is going to be more like 1.2G. That can also be skewed by the amount of banking. So the question would be how are we measuring the lean angle: against vertical or in relation to the road's camber? You can be perpendicular to the road in a steeply banked turn and register 20 degrees of lean from vertical...

  • Thanks 1

Share this post


Link to post
Share on other sites
21 hours ago, Dylan Code said:

Regarding the graphic of lean angle and G-force above: that would only hold true if the motorcycle had a theoretical "zero width tire". The apparent lean angle and the effective lean angle are different on a motorcycle due to the contact patch being off to the side versus straight down the center line of the motorcycle...

That is accurate, the frames (and suspensions) of motorcycles with tires of wide section will lean a few degrees more than the theorical lean angle shown in the graphic, which is the angle formed between a vertical line (the direction of gravity) and another line connecting the contact patches and the combined center of gravity of bike plus rider (please see first attached diagram of gravity and lateral forces).

Hanging off reduces that difference, even eliminating it, as we discussed on these old threads:

http://forums.superbikeschool.com/topic/3324-hanging-off-mathematically-quantified/?page=2

http://forums.superbikeschool.com/topic/3661-body-position-and-cog/

Note that in the case shown in that third picture-diagram of forces (Stoner's), the combined CG is relocated sideways enough to exactly compensate for the off-center relocation of the contact patch, reducing the actual lean angle of the suspensions and frame and increasing angular clearance.

EDC1021A-AFDF-4176-905C-BECFEDE5DFB8.png

2804FDD7-50CF-4AB9-BA12-1F0D6DC6F559.jpeg

003C1BED-26DD-48EB-BB57-BFBD7F540443.jpeg

Share this post


Link to post
Share on other sites

So if a MotoGP rider is leaned over in a corner on flat ground at 63 degrees of lean, what do you think the lateral acceleration is?

Share this post


Link to post
Share on other sites
On 2/6/2019 at 11:19 PM, Dylan Code said:

So if a MotoGP rider is leaned over in a corner on flat ground at 63 degrees of lean, what do you think the lateral acceleration is?

Approximately 1.96 g.   That magnitude would be approximately the result of multiplying the standard acceleration due to gravity (32.2 feet/second square) by the tangent of 63 degrees (1.96).   That means that, depending on specific front-rear weight distribution, each contact patch would be feeling a lateral force (trying to make it slide over) which magnitude would be a little less than the combined static weight of bike, fluids and rider.  That makes that rubber compund a fantastic sticky and resilient material.

The IMU (Intertial Measurement Unit) in the MotoGP bike is made up of gyroscopes and accelerometers (usually a 6-axis system) that gather information on the bike’s chassis attitude.  Because the previous research we did here (above picture), we can assume that with proper hang-off of the rider, the tire-width offset is compensated in such a way that the chassis lean angle is pretty close to the theorical dynamic lean angle (line of combined CG to centers of contact patches respect to vertical).

The concept that I would like to present to new riders is that the magnitude of lean angle always follows the magnitude of those lateral forces, which we create by selecting the speed of cornering for a particular curve.   In other words, although we surely can improve the chassis lean angle by hanging-off, we can't directly manipulate or choose the theorical dynamic lean angle of the bike, which is a natural balancing reaction (the CG-frame-tires aligns with the new resultant leaned force of cornering) and only depends on the square of the speed and on the radius of the trajectory we choose.

  • Like 1

Share this post


Link to post
Share on other sites

I don't think we will ever see a motorcycle pull 1.96 lateral G's on flat ground this lifetime. For comparison a Superkart on the skidpad did 1.39g in one test. In the same test a Williams F1 car with 0.5G downforce was able to do 2.0G on a track in a fast, banked corner aided by the wings for road holding. An Ariel Atom, known for its cornering, can only mange 1.12G, a Ferrari LaFerrari comes in a 1.16G. I think your calculations may be based off of some assumptions regarding the contact patch and it's location for the effective lean angle figure vs frame lean angle. I'm looking at a datalog of a moto2 bike at Aragon ridden by a world level rider, fastest lap, banked turn, and coming up with a max lateral acceleration of 1.42G as a momentary peak. The key point being that it's a banked turn.

  • Thanks 1

Share this post


Link to post
Share on other sites

It could be off some degree.  As far as I understand it, the lean angle shown in the display of a MotoGP is calculated based on the rate of leaning over speed from a vertical, using radial acceleration data supplied by the IMU.  Because the inertial reference of the bike changes when cornering, there is no way for the blind (it has no horizon visual reference) IMU to directly "feel" and measure lean angle.  Any blindfolded passenger of that bike would be lost about angle as well, his/her only clue about the intensity of cornering and resulting lean would be the sensation of increased body weight.  The only accurate way to calculate the lateral acceleration and resulting force is by accurately knowing both speed and radius of the trajectory.

I understand that chassis lean angle is the most evident clue that we normally have to guess how much stress we are putting on the contact patches, but the above graphic of lateral g-acceleration versus angle of lean shows us that strees-angle relation is not linear.  What amazed me about this remarkable article written by Keith ten years ago was the fact he exposed (opening my eyes to this phenomena) about the needed finesse required when approaching maximum lean angle due to the rapid increase on dynamic forces, loads and stresses:

"The barriers then are both physical sensation and visual orientation, and I believe there is a make-or-break point. That point is 45 degrees of lean. At 45 degrees, the forces are a bit out of the ordinary. Along with the normal 1g down, we now also have a 1g lateral load. As a result, the bike and our bodies experience an increase in weight. That's not native to us, and acts as both a distraction and a barrier.

Once we become comfortable with 45 degrees and attempt to go beyond that, the process begins to reverse. Immediately we have more lateral load than vertical load, and things begin to heat up. Riders apparently have difficulty organizing this. Suddenly, we are thrust into a sideways world where the forces escalate rapidly. While it takes 45 degrees to achieve 1g lateral, it takes only 15 degrees more to experience nearly double that (depending on rider position and tire size)."

https://www.motorcyclistonline.com/leaning-bike-code-break

  • Like 1

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

×
×
  • Create New...