ninjette.org

Go Back   ninjette.org > General > Riding Skills

Notices

Reply
 
Thread Tools
Old April 16th, 2016, 04:28 PM   #1
akima
Nooblet
 
akima's Avatar
 
Name: Akima
Location: England
Join Date: Jul 2011

Motorcycle(s): 2011 Ninja 250R FI

Posts: A lot.
Blog Entries: 5
MOTM - Oct '13
Question Front/Rear Weight Distribution Vs Contact Patch

Imagine a road that is clean, smooth and has an even surface. You approach a corner on this road with your throttle even and steady. You don't apply any acceleration and you don't decelerate as you take the corner.

On bike designed with perfectly balanced weight distribution between the front and rear, I'd expect the front and rear tyres to share the grip requirement evenly: 50/50. The rear tyre would likely be a wider tyre with a bigger contact patch so it would be capable of maintaining more grip than the front tyre. So if you take the corner I described at such a speed that you reach the traction limit of the bike then I would expect the front wheel to give-out first as the front tyre is thinner (smaller contact patch).

What I've been told is that you should accelerate through the corner in order to move that 50/50 weight distribution I mentioned above towards more of a 70/30 (rear/front) weight distribution.

Something I struggle with is the fact that if you accelerate through a corner, although you are shifting weight to the rear (taking grip-demand off the front and transferring it to the rear), you are also increasing the size of the rear-tyre contact patch and decreasing front-tyre contact patch. So although you are taking grip-demand off the front (by reducing weight) you are also taking grip-capacity off the front (due to the shrinking front contact patch).

Is it the case then that that changing of the size of the tyre contact patch makes far less difference than the effect of transferring weight front one tyre to the other? If the opposite was true and the contact patch made more of a difference than the weight distribution, then presumably the advice would be to decelerate as you go around a corner in order to increase the size of the front wheel contact patch.

Based on what I've written does it sound like I understand this all correctly? (I know that my terminology isn't great)
__________________________________________________
akima is offline   Reply With Quote


1 out of 1 members found this post helpful.


Old April 16th, 2016, 04:38 PM   #2
SLOWn60
n00bie to wannabie
 
SLOWn60's Avatar
 
Name: Bill
Location: St Ives, BC (Shuswap Lake)
Join Date: Sep 2015

Motorcycle(s): 2012 250R (Red), 2005 VFR800A (Red), CRF450X (Red), 2012 F800GS (Wants to be Red!)

Posts: A lot.
MOTM - Nov '15
Your 50/50 assumption may be wrong. If you were to weigh on a scale you'll likely find there is more weight on the back tire than the front. Add the G Force multiplier when cornering and the discrepancy increases.
None of that answers your question but would be a contributing factor.
__________________________________________________
The Smart Money: #1 - ATGATT, #2 - Training (machine skills and survival skills), #3 - The bike; whatever floats yer boat with the money you have left over
SLOWn60 is offline   Reply With Quote


Old April 16th, 2016, 05:21 PM   #3
HoneyBadgerRy
ninjette.org certified postwhore
 
HoneyBadgerRy's Avatar
 
Name: Ryan
Location: Beaufort SC
Join Date: Aug 2015

Motorcycle(s): 05 Ninja 250, 04 KTM 625 SMC, 01 Xc250

Posts: A lot.
Blog Entries: 3
Idk if this adds anything, but I corner better when I drag the rear brake.

Also most bikes are weight biased towards the front.

Supermoto guys put their leg on the front axle on sharp slow turns and stick their knee out in wider fast turns.

I try to keep my weight forward, and its a lot easier to save the rear when I loose it then to save the front after I lost it. (Both are save able though).
__________________________________________________
Because Unregistered sucks at riding.
HoneyBadgerRy is offline   Reply With Quote


Old April 16th, 2016, 05:36 PM   #4
adouglas
Cat herder
 
adouglas's Avatar
 
Name: Gort
Location: A secret lair which, being secret, has an undisclosed location
Join Date: May 2009

Motorcycle(s): Aprilia RS660

Posts: A lot.
Blog Entries: 6
MOTM - Jul '18, Nov '16, Aug '14, May '13
Assuming both tires are at the same pressure and both tires have the same carcass stiffness, the size of the contact patches in a 50/50 weight distribution scenario must by definition be equal.

What will differ is the shape of the contact patch.

But to answer your question, take a look at your typical low side crash during a MotoGP race. What's happening there? Answer: The rider is trail-braking too deep into the corner and exceeding the traction limits of the front tire, thereby "tucking" it. Too much lean plus too much load (i.e. deceleration) and the tire gives up. Increasing the size of the contact patch by loading the front does not give you unlimited grip.

Take a look: Valentino is still leaned over a bit and in the last part of their turn when the front wheel comes off the ground under acceleration.

So there's more going on here than having the front in contact with the ground throughout the turn.

__________________________________________________
I am NOT an adrenaline junkie, I'm a skill junkie. - csmith12

Nam et ipsa scientia potestas est.
Heri historia. Cras mysterium. Hodie donum est. Carpe diem.

Last futzed with by adouglas; April 16th, 2016 at 08:32 PM.
adouglas is offline   Reply With Quote


Old April 16th, 2016, 08:48 PM   #5
Flying
ninjette.org sage
 
Name: -
Location: somewhere cold
Join Date: Jun 2013

Motorcycle(s): 2010 Ninja 250

Posts: 596
Blog Entries: 1
Quote:
Originally Posted by akima View Post
Is it the case then that that changing of the size of the tyre contact patch makes far less difference than the effect of transferring weight front one tyre to the other? If the opposite was true and the contact patch made more of a difference than the weight distribution, then presumably the advice would be to decelerate as you go around a corner in order to increase the size of the front wheel contact patch.
- The change in the size of the contact patch is dependent on the normal (vertical) load among other things (amount of slip/lateral load/magic properties of rubber). One can't really be said to have more of an effect than the other.
- The effect of changing the size of the contact patch through weight transfer is determined/limited by the characteristics of the tire you are loading.
- You're right in suspecting that size isn't everything. :O

The effect you seek, ideal cornering at so-and-so speed, is determined by the tires and how you manage the weight transfer (accel/deccel). The opposite situation you propose might work if you reversed the tire sizes of the front and rear.

These guys really like to brake mid-corner:
http://forums.mtbr.com/all-mountain/...hy-783624.html

Last futzed with by Flying; April 17th, 2016 at 08:37 AM.
Flying is offline   Reply With Quote


1 out of 1 members found this post helpful.
Old April 16th, 2016, 09:37 PM   #6
cbinker
Track Clown
 
cbinker's Avatar
 
Name: Chris
Location: Kingman, AZ
Join Date: May 2012

Motorcycle(s): '08 250R, 21 MV F3 800, Kawasaki 400 build

Posts: A lot.
MOTM - Sep '15
check out the twist of the wrist books.
__________________________________________________

TEAM ALFALFA
www.apexassassins.com
cbinker is offline   Reply With Quote


1 out of 1 members found this post helpful.
Old April 16th, 2016, 09:46 PM   #7
Flying
ninjette.org sage
 
Name: -
Location: somewhere cold
Join Date: Jun 2013

Motorcycle(s): 2010 Ninja 250

Posts: 596
Blog Entries: 1
This is a good time to ask "how do tires make the turn"?
In addition to the pic of Rossi managing a turn w/ no front... How do unicycles turn at all?

At this point you ought to pirate/buy/borrow and read Miliken's Race Car Vehicle Dynamics supplemented by good ol Tune to Win.

Lateral tire forces, slip angles, and spooky voodoo tire graphs are the game here.
Flying is offline   Reply With Quote


2 out of 2 members found this post helpful.
Old April 17th, 2016, 12:00 AM   #8
akima
Nooblet
 
akima's Avatar
 
Name: Akima
Location: England
Join Date: Jul 2011

Motorcycle(s): 2011 Ninja 250R FI

Posts: A lot.
Blog Entries: 5
MOTM - Oct '13
Thanks for the responses. My brain is still churning over trying to figure this out.
__________________________________________________
akima is offline   Reply With Quote


Old April 17th, 2016, 07:15 AM   #9
Motofool
Daily Ninjette rider
 
Motofool's Avatar
 
Name: Hernan
Location: Florida
Join Date: Mar 2011

Motorcycle(s): 2007 Ninja 250

Posts: A lot.
MOTY - 2016, MOTM - Dec '12, Jan '14, Jan '15, May '16
Cool

Quote:
Originally Posted by akima View Post
.........Something I struggle with is the fact that if you accelerate through a corner, although you are shifting weight to the rear (taking grip-demand off the front and transferring it to the rear), you are also increasing the size of the rear-tyre contact patch and decreasing front-tyre contact patch. So although you are taking grip-demand off the front (by reducing weight) you are also taking grip-capacity off the front (due to the shrinking front contact patch).

Is it the case then that that changing of the size of the tyre contact patch makes far less difference than the effect of transferring weight front one tyre to the other? If the opposite was true and the contact patch made more of a difference than the weight distribution, then presumably the advice would be to decelerate as you go around a corner in order to increase the size of the front wheel contact patch.

Based on what I've written does it sound like I understand this all correctly? (I know that my terminology isn't great)
Yours is a very interesting observation, Akima.
Your reasoning is accurate:
https://www.ninjette.org/forums/show...5&postcount=32

Pure friction (attraction forces at molecular level) depends only on the nature of the surfaces in contact and on the force that is normal or perpendicular to the surfaces; nothing to do with area of contact.

Traction of a tire over pavement deviates a little from that concept because the rubber tends to fill up the cavities of the pavement's surface, creating an additional mechanical interlock that resists skids and slides.
That additional grip depends on the softness of the rubber and the pressure of inflation of the tire.

That traction is also dynamic; hence, irregularities or undulations of the surface, as well as camber of the road, combined with the speed of the bike and the response of the suspension mechanism is constantly changing both, the normal force and the area of contact.

The combination of flexible rubber, deformable carcass, rotating tire and lateral forces create a crabbing effect; therefore, the tire cannot follow the path that a rigid wheel would follow.
That is an additional twisting effect on the contact patch that makes it less complying with the roughness of the surface: less available traction when that is happening.

The rear contact patch can:
1) Have X area of contact while it supports its share of weight distribution (50~60% solo or 70~85% luggage-passenger) during non-accelerated conditions (just riding at constant speed on a straight street).
2) Have 120% of X area of contact while it supports the total weight of bike plus rider during a wheelie (even more load if a leaned wheelie like the picture above).
3) Have zero area of contact while it is in the air during a stoppie or hard breaking.

Accelerating during a turn artificially loads and hardens the rear suspension (bad for rear traction), but it lifts the points of the bike that could drag over the road or track (good for more clearance) and unloads and makes more complying the front suspension (easier for the tire to follow road undulations = front contact patch keep contact with surface and suffers less dramatic changes of shape = good for front traction).
It also moves the whole dynamics away from the influence of the nervous steering (sudden changes of trajectory and induced lateral forces/deformations) of the front tire and closer to the more stable condition of a coin describing a circular trajectory while leaned (unicycle or motorcycle during a leaned wheelie).

__________________________________________________
Motofool
.................................Never ride faster than your guardian angel can fly
"Mankind is composed of two sorts of men — those who love and create, and those who hate and destroy. Love is the bond between men, the way to teach and the center of the world." - José Martí
Motofool is offline   Reply With Quote


1 out of 1 members found this post helpful.
Old April 17th, 2016, 09:37 AM   #10
HoneyBadgerRy
ninjette.org certified postwhore
 
HoneyBadgerRy's Avatar
 
Name: Ryan
Location: Beaufort SC
Join Date: Aug 2015

Motorcycle(s): 05 Ninja 250, 04 KTM 625 SMC, 01 Xc250

Posts: A lot.
Blog Entries: 3
Quote:
Originally Posted by Motofool View Post
Yours is a very interesting observation, Akima.
Your reasoning is accurate:
https://www.ninjette.org/forums/show...5&postcount=32

Pure friction (attraction forces at molecular level) depends only on the nature of the surfaces in contact and on the force that is normal or perpendicular to the surfaces; nothing to do with area of contact.

Traction of a tire over pavement deviates a little from that concept because the rubber tends to fill up the cavities of the pavement's surface, creating an additional mechanical interlock that resists skids and slides.
That additional grip depends on the softness of the rubber and the pressure of inflation of the tire.

That traction is also dynamic; hence, irregularities or undulations of the surface, as well as camber of the road, combined with the speed of the bike and the response of the suspension mechanism is constantly changing both, the normal force and the area of contact.

The combination of flexible rubber, deformable carcass, rotating tire and lateral forces create a crabbing effect; therefore, the tire cannot follow the path that a rigid wheel would follow.
That is an additional twisting effect on the contact patch that makes it less complying with the roughness of the surface: less available traction when that is happening.

The rear contact patch can:
1) Have X area of contact while it supports its share of weight distribution (50~60% solo or 70~85% luggage-passenger) during non-accelerated conditions (just riding at constant speed on a straight street).
2) Have 120% of X area of contact while it supports the total weight of bike plus rider during a wheelie (even more load if a leaned wheelie like the picture above).
3) Have zero area of contact while it is in the air during a stoppie or hard breaking.

Accelerating during a turn artificially loads and hardens the rear suspension (bad for rear traction), but it lifts the points of the bike that could drag over the road or track (good for more clearance) and unloads and makes more complying the front suspension (easier for the tire to follow road undulations = front contact patch keep contact with surface and suffers less dramatic changes of shape = good for front traction).
It also moves the whole dynamics away from the influence of the nervous steering (sudden changes of trajectory and induced lateral forces/deformations) of the front tire and closer to the more stable condition of a coin describing a circular trajectory while leaned (unicycle or motorcycle during a leaned wheelie).

I know I get yelled at for ripping on peoples stats all the time on here, but I gotta do out again.

If all the weight of the vehicle luggage and rider is on the rear tire, how could there be more when the bike is leaned over?
__________________________________________________
Because Unregistered sucks at riding.
HoneyBadgerRy is offline   Reply With Quote


Old April 17th, 2016, 09:45 AM   #11
SLOWn60
n00bie to wannabie
 
SLOWn60's Avatar
 
Name: Bill
Location: St Ives, BC (Shuswap Lake)
Join Date: Sep 2015

Motorcycle(s): 2012 250R (Red), 2005 VFR800A (Red), CRF450X (Red), 2012 F800GS (Wants to be Red!)

Posts: A lot.
MOTM - Nov '15
Quote:
Originally Posted by HoneyBadgerRy View Post
I know I get yelled at for ripping on peoples stats all the time on here, but I gotta do out again.

If all the weight of the vehicle luggage and rider is on the rear tire, how could there be more when the bike is leaned over?
http://www.youtube.com/watch?v=db0a29kRxTc&sns=em
__________________________________________________
The Smart Money: #1 - ATGATT, #2 - Training (machine skills and survival skills), #3 - The bike; whatever floats yer boat with the money you have left over
SLOWn60 is offline   Reply With Quote


Old April 17th, 2016, 10:15 AM   #12
Motofool
Daily Ninjette rider
 
Motofool's Avatar
 
Name: Hernan
Location: Florida
Join Date: Mar 2011

Motorcycle(s): 2007 Ninja 250

Posts: A lot.
MOTY - 2016, MOTM - Dec '12, Jan '14, Jan '15, May '16
Cool

Quote:
Originally Posted by SLOWn60 View Post
One summer evening in ancient Greek ........



Quote:
Originally Posted by HoneyBadgerRy View Post
I know I get yelled at for ripping on peoples stats all the time on here, but I gotta do out again.

If all the weight of the vehicle luggage and rider is on the rear tire, how could there be more when the bike is leaned over?
No need to yell or get yelled at; we are here to discuss and learn while we have fun.

Because weight is a force that normally pull us down.
When a satellite or an astronaut is weightless, it is so because there is a force pulling it/her/him up that cancels the force pulling down.
Both forces are equal and have opposite different directions.

The force pulling up is the result of the circular movement and the one pulling down is caused by gravity.
__________________________________________________
Motofool
.................................Never ride faster than your guardian angel can fly
"Mankind is composed of two sorts of men — those who love and create, and those who hate and destroy. Love is the bond between men, the way to teach and the center of the world." - José Martí
Motofool is offline   Reply With Quote


0 out of 1 members found this post helpful.
Old April 17th, 2016, 10:20 AM   #13
HoneyBadgerRy
ninjette.org certified postwhore
 
HoneyBadgerRy's Avatar
 
Name: Ryan
Location: Beaufort SC
Join Date: Aug 2015

Motorcycle(s): 05 Ninja 250, 04 KTM 625 SMC, 01 Xc250

Posts: A lot.
Blog Entries: 3
Quote:
Originally Posted by SLOWn60 View Post
Well that was a waste of 7 minutes of my life.

A motorcycle doesn't have any down force, the only force acting on it is gravity, it can only have the amount of force equlivant to its weight acting on it. All of its weight has to be spread across its parts touching the ground. If that is the two tires it is spread across those two tires in a certial ratio depending on a number of things. If the only contact to the ground is the front (like in heave braking) 100% of the weight is on the front. If the only contact is the rear (like in heavy acceleration) then 100% of the weight is on the rear.
__________________________________________________
Because Unregistered sucks at riding.
HoneyBadgerRy is offline   Reply With Quote


Old April 17th, 2016, 10:21 AM   #14
HoneyBadgerRy
ninjette.org certified postwhore
 
HoneyBadgerRy's Avatar
 
Name: Ryan
Location: Beaufort SC
Join Date: Aug 2015

Motorcycle(s): 05 Ninja 250, 04 KTM 625 SMC, 01 Xc250

Posts: A lot.
Blog Entries: 3
Quote:
Originally Posted by Motofool View Post
One summer evening in ancient Greek ........





No need to yell or get yelled at; we are here to discuss and learn while we have fun.

Because weight is a force that normally pull us down.
When a satellite or an astronaut is weightless, it is so because there is a force pulling it/her/him up that cancels the force pulling down.
Both forces are equal and have opposite different directions.

The force pulling up is the result of the circular movement and the one pulling down is caused by gravity.
I have had 120 days worth if physics class.
__________________________________________________
Because Unregistered sucks at riding.
HoneyBadgerRy is offline   Reply With Quote


Old April 17th, 2016, 11:11 AM   #15
Motofool
Daily Ninjette rider
 
Motofool's Avatar
 
Name: Hernan
Location: Florida
Join Date: Mar 2011

Motorcycle(s): 2007 Ninja 250

Posts: A lot.
MOTY - 2016, MOTM - Dec '12, Jan '14, Jan '15, May '16
Cool

Quote:
Originally Posted by HoneyBadgerRy View Post
........ A motorcycle doesn't have any down force, the only force acting on it is gravity, it can only have the amount of force equlivant to its weight acting on it. All of its weight has to be spread across its parts touching the ground. If that is the two tires it is spread across those two tires in a certial ratio depending on a number of things. If the only contact to the ground is the front (like in heave braking) 100% of the weight is on the front. If the only contact is the rear (like in heavy acceleration) then 100% of the weight is on the rear.
That is correct.
Maybe I used the wrong words while trying to explain the load or total force that a contact patch "feels".

Let's rewind:
Assuming that both bikes and riders weight exactly the same in repose, do you see any difference in the load that each contact patch is supporting?



__________________________________________________
Motofool
.................................Never ride faster than your guardian angel can fly
"Mankind is composed of two sorts of men — those who love and create, and those who hate and destroy. Love is the bond between men, the way to teach and the center of the world." - José Martí
Motofool is offline   Reply With Quote


Old April 17th, 2016, 11:13 AM   #16
HoneyBadgerRy
ninjette.org certified postwhore
 
HoneyBadgerRy's Avatar
 
Name: Ryan
Location: Beaufort SC
Join Date: Aug 2015

Motorcycle(s): 05 Ninja 250, 04 KTM 625 SMC, 01 Xc250

Posts: A lot.
Blog Entries: 3
Quote:
Originally Posted by Motofool View Post
That is correct.
Maybe I used the wrong words while trying to explain the load or total force that a contact patch "feels".

Let's rewind:
Assuming that both bikes and riders weight exactly the same in repose, do you see any difference in the load that each contact patch is supporting?



The contact patch could be different, but the load would be the same.

Edit: same amount of force. Not quite the same I guess. The moto go guy would have the load traveling in a diagonal forward down direction. The stunter would be almost straight down.
__________________________________________________
Because Unregistered sucks at riding.
HoneyBadgerRy is offline   Reply With Quote


Old April 17th, 2016, 11:38 AM   #17
Motofool
Daily Ninjette rider
 
Motofool's Avatar
 
Name: Hernan
Location: Florida
Join Date: Mar 2011

Motorcycle(s): 2007 Ninja 250

Posts: A lot.
MOTY - 2016, MOTM - Dec '12, Jan '14, Jan '15, May '16
Cool

Quote:
Originally Posted by HoneyBadgerRy View Post
The contact patch could be different, but the load would be the same.

Edit: same amount of force. Not quite the same I guess. The moto go guy would have the load traveling in a diagonal forward down direction. The stunter would be almost straight down.
Same load, different directions?
__________________________________________________
Motofool
.................................Never ride faster than your guardian angel can fly
"Mankind is composed of two sorts of men — those who love and create, and those who hate and destroy. Love is the bond between men, the way to teach and the center of the world." - José Martí
Motofool is offline   Reply With Quote


Old April 17th, 2016, 12:16 PM   #18
HoneyBadgerRy
ninjette.org certified postwhore
 
HoneyBadgerRy's Avatar
 
Name: Ryan
Location: Beaufort SC
Join Date: Aug 2015

Motorcycle(s): 05 Ninja 250, 04 KTM 625 SMC, 01 Xc250

Posts: A lot.
Blog Entries: 3
Quote:
Originally Posted by Motofool View Post
Same load, different directions?
The stunted is stopped, so he is balancing the bike vertically. The moto go guy is stopping the bike, so the tire is being compressed and dragged. Its a vertical vs a horizontal load. Even though they both have a vertical and a horizontal load.
__________________________________________________
Because Unregistered sucks at riding.
HoneyBadgerRy is offline   Reply With Quote


Old April 17th, 2016, 01:08 PM   #19
SLOWn60
n00bie to wannabie
 
SLOWn60's Avatar
 
Name: Bill
Location: St Ives, BC (Shuswap Lake)
Join Date: Sep 2015

Motorcycle(s): 2012 250R (Red), 2005 VFR800A (Red), CRF450X (Red), 2012 F800GS (Wants to be Red!)

Posts: A lot.
MOTM - Nov '15
The loads aren't the same. You're not accounting for the increase in load added from deceleration. The higher the rate of deceleration; the higher the increased load. Same with leaned over or g force: if at static the front tire has a load of 200 lbs and the rear 300 and cornering g's of .75; the front tire is loaded 200x(1+.75)= 350 lbs and the rear 300x(1+.75)= 575 lbs. The static front/rear loading difference is 100 lbs, the dynamic difference is 275 lbs assuming no acceleration or deceleration forces are added.
__________________________________________________
The Smart Money: #1 - ATGATT, #2 - Training (machine skills and survival skills), #3 - The bike; whatever floats yer boat with the money you have left over
SLOWn60 is offline   Reply With Quote


1 out of 1 members found this post helpful.
Old April 17th, 2016, 03:25 PM   #20
akima
Nooblet
 
akima's Avatar
 
Name: Akima
Location: England
Join Date: Jul 2011

Motorcycle(s): 2011 Ninja 250R FI

Posts: A lot.
Blog Entries: 5
MOTM - Oct '13
Quote:
Originally Posted by Motofool View Post
Accelerating during a turn [...] unloads and makes more complying the front suspension (easier for the tire to follow road undulations = front contact patch keep contact with surface and suffers less dramatic changes of shape = good for front traction).
It also moves the whole dynamics away from the influence of the nervous steering (sudden changes of trajectory and induced lateral forces/deformations) of the front tire and closer to the more stable condition of a coin describing a circular trajectory while leaned (unicycle or motorcycle during a leaned wheelie).
Thanks for the feedback Motofool (and others). I had a feeling that my reasoning would be roughly accurate but that there were more variables involved that I wasn't factoring in. The stuff quoted above are things I didn't know about and hadn't considered.
__________________________________________________
akima is offline   Reply With Quote


Old April 17th, 2016, 03:27 PM   #21
Mohawk
ninjette.org guru
 
Mohawk's Avatar
 
Name: Chris
Location: Bristol, UK
Join Date: Feb 2016

Motorcycle(s): ZZR250, VFR800

Posts: 475
Assuming a normal single apex corner on a road, you should brake until you reach a speed at which you can safely negotiate on neutral throttle opening to reach the apex, from the apex, assumming an opening corner, you would then gradually add throttle to accelerate the bike out of the turn & back to upright.

On a race track you would reduce braking & start turning, gradually releasing the front brake once you reach maximum cornering speed, then neutral throttle to the apex & if 1. on a powerful bike, drift out from the apex on an increasing throttle until you can see the corner exit, then stand the bike up to get the fatter larger diameter i.e. maximum grip whilst using counter leaning & then give it as much gas as it will take, again if modern bike with electronics, that's everything & let the bike work it out. You can steer on one wheel, ask a uni-cyclist ! if 2. a low powered bike, you add throttle as fast as is safe to NOT exceed rear grip (to avoid possible high side !) & allow bike to drift out of corner to full upright & maximum power ASAP.

Bikes with the same size front/rear tyres handle best in a classic fashion, i.e. no hanging off or counter weighting. Check out a road bicycle !

Narrower front/wider rear handles best with modern riding style, wider rear gives more grip to deal with modern power levels.

Different rubber compounds & tyre profiles will improve/reduce grip at different lean angles.

YMMV
Mohawk is offline   Reply With Quote


Old April 18th, 2016, 08:41 PM   #22
Motofool
Daily Ninjette rider
 
Motofool's Avatar
 
Name: Hernan
Location: Florida
Join Date: Mar 2011

Motorcycle(s): 2007 Ninja 250

Posts: A lot.
MOTY - 2016, MOTM - Dec '12, Jan '14, Jan '15, May '16
Cool

Quote:
Originally Posted by akima View Post
Thanks for the feedback Motofool (and others). I had a feeling that my reasoning would be roughly accurate but that there were more variables involved that I wasn't factoring in. The stuff quoted above are things I didn't know about and hadn't considered.
You are welcome, Akima

Some of the variables may be not exactly as described above, but that is how I understand those from books and from my own observations.

Any proficient motorcyclist should know and constantly feel what is going on in the small yet very important contact patches of the tires.

He/she may like or not exploring the limits of traction during cornering, braking and accelerating.
Inadvertently reaching those limits at the wrong moment and place is something that could end the enjoyment of a long lasting motorcycling career.

Develop a fine perception of balance, acceleration, gravity, road's surface roughness and contamination, as well as relative position, temperature, deformation and stress of contact patches.
IMHO opinion, that is a key skill to develop, as valuable as proper vision skills.

__________________________________________________
Motofool
.................................Never ride faster than your guardian angel can fly
"Mankind is composed of two sorts of men — those who love and create, and those who hate and destroy. Love is the bond between men, the way to teach and the center of the world." - José Martí
Motofool is offline   Reply With Quote


1 out of 1 members found this post helpful.
Old April 18th, 2016, 09:18 PM   #23
csmith12
The Corner Whisperer
 
csmith12's Avatar
 
Name: Chris (aka Reactor)
Location: Northern KY
Join Date: May 2011

Motorcycle(s): 2010 250 (track), 1992 250, 2006 R6 (street/track), 2008 R6 (track)

Posts: Too much.
MOTY 2015, MOTM - Nov '12, Nov '13
@akima, this is all very well and vetted out by people wearing lab coats in TOTW2 movie. lol They even get out the scales to measure weight on each tire and calipers to measure the contact patch size. You should watch it.

Some common goals for a sportbike;

Achieve a 50/50 weight distro via good solid chassis design, geometry & suspension adjustments. The bike cannot account for the rider moving around on it. Although this may change in the future with active electronics making suspension changes while in motion. Can your bike adjust on the fly if you slide all the way front and aft in the seat?

More weight on the front is beneficial when initiating a turn, raising the rear of a 250 is an example mod that is done to many race bikes to help the bike turn faster but at the cost of a less stable chassis. A taller rear of the bike changes the geometry, shortens the wheelbase and does slightly front load the weight. This in turn helps flatten the fronts contact patch for maximum traction at the turn point.

Once under INCREASED cornering load, which contact patch can handle more load? The bigger one or smaller one? And how do you get the load distributed? When rolling on the throttle, the rear of the bike rises... why? Because the engine pulls the chain, the chain is connected to the rear tire, which is at the end of the swingarm. The swingarm pivots at its mount point near the front sprocket. The force of the engine pulls the ENTIRE swingarm down, thus raising the ENTIRE bike, good for ground clearance, but bad for traction because we want the shock to keep the tire on the ground. What is better for maximum traction? A smooth throttle roll or an aggressive one? Maybe that question is to easy... What kind of throttle roll, lets the suspension do it's best work? HINT: Do you want your engine fighting your suspension or nah?

While straight up and down (no lean) and accelerating in a straight line, it's ALL about keeping the rear from spinning up. Contact patch and friction is not enough anymore on modern high powered bikes. With the engine producing such a force on the rear, the rear shock simply can't do what it was designed to do in a nearly topped out position. Hence we have things like traction control and such to help. We don't have worry about that on 250's with such low amounts of power, but it helps to know why people say what they say.

Hope that helps you understand and if not, I will try to help you out.
csmith12 is offline   Reply With Quote


2 out of 2 members found this post helpful.
Old April 19th, 2016, 06:04 AM   #24
csmith12
The Corner Whisperer
 
csmith12's Avatar
 
Name: Chris (aka Reactor)
Location: Northern KY
Join Date: May 2011

Motorcycle(s): 2010 250 (track), 1992 250, 2006 R6 (street/track), 2008 R6 (track)

Posts: Too much.
MOTY 2015, MOTM - Nov '12, Nov '13
I wanted to go a bit further on this... because it was really, really one of the concepts I had trouble with.

The main reasons why weight distro and contact patches are so misunderstood is because your average street rider doesn't really have a clue what is truly meant by "steer with the rear". Its like some sort of voodoo and beyond some sort of bike magic that only the motogp pros are privy to.

To explain this concept in simple terms, forget motorcycles for a moment and focus on momentum and a pivot point. If momentum is moving a point around another point then the direction is constantly changing. If you can control or affect the momentum of the moving point you can change the direction. Now... let's apply that to bikes.

Let's say your front wheel is the pivot point and the rear wheel rotates around it. You can see this vividly when a rider does a circle burnout. How did he change direction? Did he steer with the rear? Did the the rear pivot around the front? Next, let's watch some semi pro and pro racers come down the back straight at 175mph and start to brake for the turn at the end. Some riders can kick out the rear prior to the turn in point, it's informally known as a "backing it in". When that rider reaches his turn point, he countersteers to a very minimum to what angle the bike is already at. Because the front and rear wheel are no longer in line with each other. Did that rider steer with the rear? Did the rear pivot around the front? Or how about this... A rider is very aggressive with the throttle mid corner and the rear slides out. Did it pivot around the front? Is the bike pointed in the same direction? How about if the rear slides and the rider chops the throttle, why does that result in a highside so often? Because when the rear regains traction, the bike wants to change direction so quickly it ejects the rider. Lastly, during stunt shows, riders may do circle wheelies. aka, turning their bikes into unicycles. The physics here are different but the fact remains that they can control the rear via the throttle to maintain or change direction.

Now what does all this have to do with contact patches!?!??!

Mr. Fist will be the first to tell you a lot. A very slow throttle roll doesn't weight the rear enough, the front contact patch is spread too large and will want to turn the bike further into the corner. Alternatively, if the rider is very heavy handed, the front's patch is too small and the bike will want to run wide in the corner. Now think about that for a moment... If turning with the bars is already done, what are you steering with? This is why only the riders who fully understand this will say "practice your roll off as much as your roll on."

More...
When doing a circle burnout, you need 100% contact and traction on the front and less in the rear. The smaller contact patch will hold the bike as there is no cornering load in effect and you want enough patch in the rear to make a lot of smoke.

When riding a liter bike exiting turn 10 at 105 mph while lofting the front in the air, the rear patch handles near 90-100% of the load as lean angle decreases and throttle is applied. It works because cornering forces decrease as lean angle decreases. Drifting is another example of pivoting that is in between a circle burnout and unicycle, but yet... still a very good example of steering with the rear. Too much gas sends the car in a spinout, too little and the car snaps back inline changing the direction quickly just like a bike.

For us normal riders, we should strive for a nice 40/60 (front/rear) via a smooth 5th gear roll on. That would be 3rd or 4th gear for us 250 riders depending on your gearing and setup. This keeps both wheels on the tarmac and takes advantage of the bikes strengths while minimizing the exposure to its weaknesses.

Last futzed with by csmith12; April 27th, 2016 at 02:57 PM. Reason: spelling
csmith12 is offline   Reply With Quote


Old April 19th, 2016, 07:42 AM   #25
csmith12
The Corner Whisperer
 
csmith12's Avatar
 
Name: Chris (aka Reactor)
Location: Northern KY
Join Date: May 2011

Motorcycle(s): 2010 250 (track), 1992 250, 2006 R6 (street/track), 2008 R6 (track)

Posts: Too much.
MOTY 2015, MOTM - Nov '12, Nov '13


And one more thing.... You don't have to be old enough to understand the concept to make it work for you. lol

Link to original page on YouTube.

csmith12 is offline   Reply With Quote


1 out of 1 members found this post helpful.
Old April 19th, 2016, 10:02 AM   #26
choneofakind
ninjette.org certified postwhore
 
Name: .
Location: .
Join Date: Feb 2011

Motorcycle(s): .

Posts: Too much.
MOTM - Feb '13, Feb '14
Quote:
Originally Posted by HoneyBadgerRy View Post
I have had 120 days worth if physics class.
...that's cute.
choneofakind is offline   Reply With Quote


Old April 19th, 2016, 10:09 AM   #27
HoneyBadgerRy
ninjette.org certified postwhore
 
HoneyBadgerRy's Avatar
 
Name: Ryan
Location: Beaufort SC
Join Date: Aug 2015

Motorcycle(s): 05 Ninja 250, 04 KTM 625 SMC, 01 Xc250

Posts: A lot.
Blog Entries: 3
Quote:
Originally Posted by choneofakind View Post
...that's cute.
Its enough that I am not a complete newb. I guess I should have said 2 college credits, but I didn't.
__________________________________________________
Because Unregistered sucks at riding.
HoneyBadgerRy is offline   Reply With Quote


Old April 19th, 2016, 10:17 AM   #28
choneofakind
ninjette.org certified postwhore
 
Name: .
Location: .
Join Date: Feb 2011

Motorcycle(s): .

Posts: Too much.
MOTM - Feb '13, Feb '14
Quote:
Originally Posted by csmith12 View Post
Drifting is another example of pivoting that is in between a circle burnout and unicycle, but yet... still a very good example of steering with the rear. Too much gas sends the car in a spinout, too little and the car snaps back inline changing the direction quickly just like a bike.
From the textbook, drifting is kind of a special case. The driver is manipulating multiple variables at once.

Understeer at steady state is defined as the front tires losing traction before the rear, measured in positive degrees of steering wheel change per g of lateral acceleration.

Oversteer at steady state is defined as the rear tires losing traction before the front, measured in negative degrees of steering wheel change per g of lateral acceleration. The interesting part about oversteer is that there exists some critical speed where an oversteering car is able to complete a steady state corner with 0 steering angle and it continuously slides/rotates with some slip angle relative to the direction it is traveling.

Drifting is unique because the driver intentionally reduces traction at the rear in order to require a large negative change in the steering wheel to keep a constant radius of turn. The driver then modulates both the throttle and the steering input (assuming they're not already at full opposite lock) to manipulate the vehicle's slip angle. We know this is true because the coefficient of static friction between tire and road is always higher than the respective coefficient of kinetic friction. I'm not so sure I'd describe drifting as steering with the rear because by spinning the tires faster or slower (modulating the throttle), the driver is actually changing the amount of both lateral and tractive force at the rear wheel and changing that special critical speed to keep a steady turn radius while sliding. It's not really steering, per say.

Vehicle dynamics are fascinating and complex. I highly recommend checking out Fundamentals of Vehicle Dynamics by Thomas Gillespie (easy to read and good explainations) or Race Car Vehicle Dynamics by Douglas Milliken (much more technical and harder to follow as a newbie, but is the accepted bible of vehicle dynamics).
choneofakind is offline   Reply With Quote


1 out of 1 members found this post helpful.
Old April 19th, 2016, 10:36 AM   #29
Panda
not an actual panda
 
Name: dan
Location: philadelphia
Join Date: Aug 2012

Motorcycle(s): 2008 Ninja 250, 2009 CBR600RR (Sold)

Posts: A lot.
Quote:
Originally Posted by akima View Post
Imagine a road that is clean, smooth and has an even surface. You approach a corner on this road with your throttle even and steady. You don't apply any acceleration and you don't decelerate as you take the corner.

On bike designed with perfectly balanced weight distribution between the front and rear, I'd expect the front and rear tyres to share the grip requirement evenly: 50/50. The rear tyre would likely be a wider tyre with a bigger contact patch so it would be capable of maintaining more grip than the front tyre. So if you take the corner I described at such a speed that you reach the traction limit of the bike then I would expect the front wheel to give-out first as the front tyre is thinner (smaller contact patch).

What I've been told is that you should accelerate through the corner in order to move that 50/50 weight distribution I mentioned above towards more of a 70/30 (rear/front) weight distribution.

Something I struggle with is the fact that if you accelerate through a corner, although you are shifting weight to the rear (taking grip-demand off the front and transferring it to the rear), you are also increasing the size of the rear-tyre contact patch and decreasing front-tyre contact patch. So although you are taking grip-demand off the front (by reducing weight) you are also taking grip-capacity off the front (due to the shrinking front contact patch).

Is it the case then that that changing of the size of the tyre contact patch makes far less difference than the effect of transferring weight front one tyre to the other? If the opposite was true and the contact patch made more of a difference than the weight distribution, then presumably the advice would be to decelerate as you go around a corner in order to increase the size of the front wheel contact patch.

Based on what I've written does it sound like I understand this all correctly? (I know that my terminology isn't great)
Yes, this is accurate. By shifting weight to the rear you’re making the front tire less loaded, the front tire has a smaller contact patch, and the bike is harder to turn. I believe the reason that this is suggested is due to several assumptions: 1. The rider is riding well below the traction limit of the tires so the loss of traction is outweighed by the benefit of increasing chassis stability. 2. The rider is not in a decreasing radius turn. 3. The rider is not heading downhill.

Rolling on the throttle throughout the turn increase chassis stability by altering the geometry of the bike. That advice works well in these situations -

1. Set entry speed while straight up and down
2. Initiate turn until you’ve reached the desired lean angle
3. Roll on throttle throughout the duration of the turn.

The benefits of this method is that it forces the rider to think about entry speed prior to the turn. It provides a discrete set of events that need to be accomplished in series. It’s easy to understand and to learn. It creates a stable bike geometry in the turn. The negatives to this method are what you’ve already pointed out. It reduces the front contact patch and reduces the immediate ability for the front tire to take on load. Which temporarily reduces the rider’s options to react to an event that happens mid turn.
Panda is offline   Reply With Quote


2 out of 2 members found this post helpful.
Old April 19th, 2016, 10:42 AM   #30
csmith12
The Corner Whisperer
 
csmith12's Avatar
 
Name: Chris (aka Reactor)
Location: Northern KY
Join Date: May 2011

Motorcycle(s): 2010 250 (track), 1992 250, 2006 R6 (street/track), 2008 R6 (track)

Posts: Too much.
MOTY 2015, MOTM - Nov '12, Nov '13
Quote:
Originally Posted by choneofakind View Post
The interesting part about oversteer is that there exists some critical speed where an oversteering car is able to complete a steady state corner with 0 steering angle and it continuously slides/rotates with some slip angle relative to the direction it is traveling.
Cool, I don't know the full science behind it but I do know what it feels like. Sometimes you have to turn right to go left... but it sometimes needs adjustments, so you end up pulling back some of that oversteer by turning left slightly to keep the rear from swinging around too far.

I learned that 20yrs ago doing doughnuts in the tobacco warehouse parking lot. Dirt guys know all about this already.

How to start...

Link to original page on YouTube.

How to end...

Link to original page on YouTube.

csmith12 is offline   Reply With Quote


1 out of 1 members found this post helpful.
Old April 19th, 2016, 11:01 AM   #31
choneofakind
ninjette.org certified postwhore
 
Name: .
Location: .
Join Date: Feb 2011

Motorcycle(s): .

Posts: Too much.
MOTM - Feb '13, Feb '14
Two reasons I can think of wanting more weight on the rear are:

1) camber steer. Tires create lateral force in the direction they are cambered. This is why a coin turns left if you roll it and it falls to the left.

2) For a vehicle that does not steer the rear tires, your turning radius is a fixed line from your rear axle to the point where a similar line from the front wheel intersects. Yes, there's limits to this statement based on scrubbing with speed, but by reducing the weight on the front wheel, you're also putting a lot less of the lateral force to turn the vehicle on the front wheel. Let's not forget that the rider is able to pivot the front wheel relative to the vehicle, so if you're supplying a proportionately large amount of lateral force with the front wheel, the rider input has a significantly larger amount of effect on keeping the chassis steady. In my mind, that is why a bike is always smoother through a turn if you roll on the throttle and transfer weight to the rear of the bike; you've reduced the significance of any small steering inputs with the front wheel. This is also why it's so important for the rider to stay loose and relaxed.

Countersteering is how you get the bike to lean, lateral force from a cambered wheel is how the bike continues to turn once you're leaned. I don't think it's as much about front and rear contact patch size as it is about front and rear loading.

https://en.wikipedia.org/wiki/Camber_thrust


I also believe that your assumption of a static 50/50 weight distribution is wrong for a sport bike. From working with tadpole tricycles, I know they tend to perform well with 70/30 f/r static weight bias, and from looking at sporty motorcycles, I assume they carry the majority of their weight on the front wheel as during static conditions.
choneofakind is offline   Reply With Quote


1 out of 1 members found this post helpful.
Old April 19th, 2016, 11:05 AM   #32
choneofakind
ninjette.org certified postwhore
 
Name: .
Location: .
Join Date: Feb 2011

Motorcycle(s): .

Posts: Too much.
MOTM - Feb '13, Feb '14
Quote:
Originally Posted by csmith12 View Post
Cool, I don't know the fully science behind it but I do know what it feels like. Sometimes you have to turn right to go left... but it sometimes needs adjustments, so you end up pulling back some of that oversteer by turning left slightly to keep the rear from swinging around too far.

I learned that 20yrs ago doing doughnuts in the tobacco warehouse parking lot. Dirt guys know all about this already.
I love that scene!!!

Side note: isn't it amazing what our brains are able to learn and control without ever knowing what science we're actually manipulating? You can control a sliding car in the snow at 20 mph for fun, you can shoot a basketball through a net from 25' back and not hit the rim, you can keep your balance on a rocking boat, or you can be Rojo and successfully race a superbike without ever knowing what countersteering is.
choneofakind is offline   Reply With Quote


Old April 19th, 2016, 11:16 AM   #33
RacinNinja
Vintage Screwball
 
RacinNinja's Avatar
 
Name: B
Location: Washington
Join Date: Feb 2016

Motorcycle(s): 2011 Ninja 250, 2008 Ninja 250, 2019 KTM 1290SDR, 2017 FZ10

Posts: A lot.
MOTM - Mar '16
Quote:
Originally Posted by csmith12 View Post
Cool, I don't know the full science behind it but I do know what it feels like. Sometimes you have to turn right to go left... but it sometimes needs adjustments, so you end up pulling back some of that oversteer by turning left slightly to keep the rear from swinging around too far.

I learned that 20yrs ago doing doughnuts in the tobacco warehouse parking lot. Dirt guys know all about this already.

How to start...

Link to original page on YouTube.

How to end...

Link to original page on YouTube.


I spent the first decade of my motorcycling life in dirt.
__________________________________________________
Goin' fast on slow bikes!

RacinNinja is offline   Reply With Quote


Old April 19th, 2016, 11:18 AM   #34
csmith12
The Corner Whisperer
 
csmith12's Avatar
 
Name: Chris (aka Reactor)
Location: Northern KY
Join Date: May 2011

Motorcycle(s): 2010 250 (track), 1992 250, 2006 R6 (street/track), 2008 R6 (track)

Posts: Too much.
MOTY 2015, MOTM - Nov '12, Nov '13
I try to learn something new every day, which is odd for an old Ky boy. Since we put in drifting cars, it is now required to put in drifting bikes. But interesting thing is... they turn right to go left just the same as cars.

Link to original page on YouTube.

csmith12 is offline   Reply With Quote


Old April 19th, 2016, 11:21 AM   #35
csmith12
The Corner Whisperer
 
csmith12's Avatar
 
Name: Chris (aka Reactor)
Location: Northern KY
Join Date: May 2011

Motorcycle(s): 2010 250 (track), 1992 250, 2006 R6 (street/track), 2008 R6 (track)

Posts: Too much.
MOTY 2015, MOTM - Nov '12, Nov '13
@akima... sorry for getting so sideways to the op theory. You got dis, the steering with the rear point is the point where your ideas start to loose their traction and the riders skill takes over.
csmith12 is offline   Reply With Quote


Old April 19th, 2016, 11:30 AM   #36
RacinNinja
Vintage Screwball
 
RacinNinja's Avatar
 
Name: B
Location: Washington
Join Date: Feb 2016

Motorcycle(s): 2011 Ninja 250, 2008 Ninja 250, 2019 KTM 1290SDR, 2017 FZ10

Posts: A lot.
MOTM - Mar '16
If you wanna learn how to steer with the rear, go grab a dirty bike, some knobbies and some sand dunes. The front is practically useless. Your only choice is to steer with your ass.

Yes, you push the ass of the bike left to go right. Push it right to go left.

That drifting video was filmed at Oregon Raceway Park. About 2 hours from home.
__________________________________________________
Goin' fast on slow bikes!

RacinNinja is offline   Reply With Quote


Old April 19th, 2016, 12:29 PM   #37
HoneyBadgerRy
ninjette.org certified postwhore
 
HoneyBadgerRy's Avatar
 
Name: Ryan
Location: Beaufort SC
Join Date: Aug 2015

Motorcycle(s): 05 Ninja 250, 04 KTM 625 SMC, 01 Xc250

Posts: A lot.
Blog Entries: 3
^^And then if you really want to have fun, take that bike to a MX sand track with those new skills.
__________________________________________________
Because Unregistered sucks at riding.
HoneyBadgerRy is offline   Reply With Quote


Old April 19th, 2016, 03:23 PM   #38
akima
Nooblet
 
akima's Avatar
 
Name: Akima
Location: England
Join Date: Jul 2011

Motorcycle(s): 2011 Ninja 250R FI

Posts: A lot.
Blog Entries: 5
MOTM - Oct '13
Quote:
Originally Posted by csmith12 View Post
@akima... sorry for getting so sideways to the op theory. You got dis, the steering with the rear point is the point where your ideas start to loose their traction and the riders skill takes over.
No it's all good Thanks for taking the time to write all that out for me/us. It's a complex topic.

I think I have come away from this accepting that I don't really understand what's happening with my bike during a corner that well and that it's going to take me a long time to properly get it. Until the time -- that I get it -- I'm comfortable accepting the advice of those that already do.

I think my instinct takes care of most of my riding, but I like to consciously understand things too, so I can gently direct my instinct the right way. Also, so I don't have to training my instinct via trial and error. Trial and error on street bikes isn't fun.
__________________________________________________
akima is offline   Reply With Quote


1 out of 1 members found this post helpful.
Old April 19th, 2016, 05:57 PM   #39
HoneyBadgerRy
ninjette.org certified postwhore
 
HoneyBadgerRy's Avatar
 
Name: Ryan
Location: Beaufort SC
Join Date: Aug 2015

Motorcycle(s): 05 Ninja 250, 04 KTM 625 SMC, 01 Xc250

Posts: A lot.
Blog Entries: 3
Quote:
Originally Posted by akima View Post
No it's all good Thanks for taking the time to write all that out for me/us. It's a complex topic.

I think I have come away from this accepting that I don't really understand what's happening with my bike during a corner that well and that it's going to take me a long time to properly get it. Until the time -- that I get it -- I'm comfortable accepting the advice of those that already do.

I think my instinct takes care of most of my riding, but I like to consciously understand things too, so I can gently direct my instinct the right way. Also, so I don't have to training my instinct via trial and error. Trial and error on street bikes isn't fun.
A long long time ago I admitted I have no idea how to ride a MX bike, but my instinct does, and I am good at tuning the bikes, so I'm better off just keeping it that way. I couldn't for the life of me explain how to do what when X happens. But get me in the mood in X situation and I will just do what I need to do.
__________________________________________________
Because Unregistered sucks at riding.
HoneyBadgerRy is offline   Reply With Quote


Old April 19th, 2016, 06:49 PM   #40
Motofool
Daily Ninjette rider
 
Motofool's Avatar
 
Name: Hernan
Location: Florida
Join Date: Mar 2011

Motorcycle(s): 2007 Ninja 250

Posts: A lot.
MOTY - 2016, MOTM - Dec '12, Jan '14, Jan '15, May '16
Cool

Quote:
Originally Posted by akima View Post
.......... I think I have come away from this accepting that I don't really understand what's happening with my bike during a corner that well and that it's going to take me a long time to properly get it.........
If you observe the reactions of your rubber and the frame of your bike, you can understand a little more each time.

You are a conservative street rider, who frequently has to deal with wet and oily city roads.

Surviving traffic, while enjoying riding, is your first priority.
Traffic conditions sometimes force evasive or aggressive maneuvers that can demand and consume much traction.

It is important that you learn to objectively evaluate or calculate how much traction there is available at the very moment that you need to use close-to-all you have.

I frequently see street riders going around a corner at 2 mph because it is raining.
Among drivers that can see less than normal, that is a very dangerous approach to cornering on wet pavement.

Those riders do so because they have no idea of how much lateral forces the tires can take; same for using the front brake.
Over dry-clean pavement those max lateral forces are around 80% of the weight supported by a so-so street tire that is properly inflated.
If the pavement is wet and clean, that same tire can easily resist lateral forces of around 50% of the supported weight, before showing the first sign of slide.

If the pavement is contaminated with sand, mud, oil or Diesel, that percentage goes dramatically down.
Those things create a different type of friction: rolling (macroscopic or microscopic).

My first experience with rolling friction was with my 50 c.c. moped on a downhill wet curve.
It was raining and there was a long patch of mud that I could have seen, but, being 16 or 17, I never paid much attention to the conditions of the surface.

Dry or wet, the surfaces of plastic street markings and steel manhole or rails, have a much lower coefficient of friction with rubber than rough pavement.
Road surfaces made of polished concrete behaves somewhere in between those.

Being silk-smooth on the control inputs, as well as avoiding sudden changes of weight distribution, can save the unavoidable ride over slippery surfaces.
When friction is precarious, any sudden force, even if little, can break the inter-surfaces contact away and induce a slide or skid.

I believe that you could gain invaluable experience by practicing testing traction over those surfaces, dry and with some type of contamination; always away from traffic, obviously.

You don't have to lean much and risk a fall.
We all have a great traction sensor: our braking front tire.
From regularly practicing emergency braking on parking lots, I have an accurate feeling of how much my front tire can grip on dry-clean, on wet and on sandy pavement.

When I am not sure of the available traction (rainy day on unfamiliar road, for example), I use that learned feeling as a reference to test it.
I wait for a safe opportunity and progressively apply the front brake until the front tire skids, immediately releasing the lever before steering is lost.

Knowing that for the same curve and trajectory, the lateral forces on the contact patches grow with the square of the speed, I have then a rough idea of how much I need to slow down or moderate steering and braking inputs.

Please, read this:
http://www.visordown.com/advanced-ri...ips/14600.html
__________________________________________________
Motofool
.................................Never ride faster than your guardian angel can fly
"Mankind is composed of two sorts of men — those who love and create, and those who hate and destroy. Love is the bond between men, the way to teach and the center of the world." - José Martí
Motofool is offline   Reply With Quote


1 out of 1 members found this post helpful.
Reply




Similar Threads
Thread Thread Starter Forum Replies Last Post
[motorcyclistonline] - Weight, Weight, Don’t Tell Me | Cranked Ninjette Newsbot Motorcycling News 0 July 17th, 2014 09:40 AM
weight of new gen 250 rear wheel? genosr1 Ninjettes At Speed 3 December 8th, 2013 05:53 PM
New foot pegs, handlebar weight, rear hanger & peg, etc. RaceBikeRentals Motorcycle-related 7 June 14th, 2012 09:25 AM
[hell for leather] - Husqvarna 900: power, weight and power-to-weight Ninjette Newsbot Motorcycling News 0 June 29th, 2011 09:20 PM
rear end cleanup / weight loss dbotos 1986 - 2007 Ninja 250R Farkles 12 January 6th, 2011 07:10 PM


Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


Motorcycle Safety Foundation

All times are GMT -7. The time now is 04:43 AM.


Website uptime monitoring Host-tracker.com
Powered by vBulletin®
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
User Alert System provided by Advanced User Tagging (Lite) - vBulletin Mods & Addons Copyright © 2024 DragonByte Technologies Ltd.
Except where otherwise noted, all site contents are © Copyright 2022 ninjette.org, All rights reserved.