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Discussion Starter #1
I would like some explanation how tire friction works on a bike in a turn. I have read several write-ups on counter-steer and how it works. I also took the riders safety course and yes I do use counter steer. But I grew up in the stock car racing world where there is only so much lateral force you can apply to a tire before it will break loose from the pavement and out to the wall you go. I also watch the guys on SPEED's 2 Wheel Tuesdays lowsideing the bikes all the time. But at the same time I hear about guys scraping the pegs/floorboards on VN900's and I want to know how far is to far. I don't want to scrape floor boards, but I do want to know what the bike will do if an emergency arises like some little old lady pulling out in front of me.

It seems to me that there is a force exerted in the plane of the wheels as the bike leans in a corner. When you are riding straight all of this force is pushing the tire against the road. But as you lean, then a larger and larger percentage of this force starts to push horizontally to the road. It would seem that at some point there is so little downward force holding the tire to the road that it will slide across the top of the road causing a lowside. But I may be wrong and the gyro effect of counter steer compensates to a point that it is almost impossible to lowside the bike.

Any help on this would be great. Hope I haven't started an explosion of opinions. PS- I have a basic knowlege of physics, not a doctorate level. Please use simple illustrations when possible.
 

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When I took the MSF course, the instructor took a bike and asked us to tell him when he exceeded the angle for maintaining traction when leaning a bike. He had it practically lying on it's side when he said, "Believe it or not, it still hasn't passed the critical point." This was during his talk on taking a curve on a bike.

Go to this website and check their safety videos. #003 is entitled "Pegs". Perhaps it will help. (note: video quality isn't all that great, but you can understand what the speaker is saying)

http://msgroup.org/videos.aspx
 

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I would like some explanation how tire friction works on a bike in a turn. I have read several write-ups on counter-steer and how it works. I also took the riders safety course and yes I do use counter steer. But I grew up in the stock car racing world where there is only so much lateral force you can apply to a tire before it will break loose from the pavement and out to the wall you go. I also watch the guys on SPEED's 2 Wheel Tuesdays lowsideing the bikes all the time. But at the same time I hear about guys scraping the pegs/floorboards on VN900's and I want to know how far is to far. I don't want to scrape floor boards, but I do want to know what the bike will do if an emergency arises like some little old lady pulling out in front of me.

It seems to me that there is a force exerted in the plane of the wheels as the bike leans in a corner. When you are riding straight all of this force is pushing the tire against the road. But as you lean, then a larger and larger percentage of this force starts to push horizontally to the road. It would seem that at some point there is so little downward force holding the tire to the road that it will slide across the top of the road causing a lowside. But I may be wrong and the gyro effect of counter steer compensates to a point that it is almost impossible to lowside the bike.

Any help on this would be great. Hope I haven't started an explosion of opinions. PS- I have a basic knowlege of physics, not a doctorate level. Please use simple illustrations when possible.
Anyone who rides a motorcycle past oh, say 15-20 MPH is countersteering whether they know it or not. As for everything else you mentioned, I'd recommend some reading, like "Sport Riding Techniques" by Nick Ienatsch. I know it says "sport riding", but it's a great book with the answers you're looking for. Also, under normal conditions on a relatively clean road you're going to run out of ground clearance before you'd ever have to worry about losing traction and having a low side, that is unless you're trying to turn while getting on the brakes pretty hard at the same time. Read the book, you'll understand.
 

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Go to this website and check their safety videos. #003 is entitled "Pegs". Perhaps it will help. (note: video quality isn't all that great, but you can understand what the speaker is saying)

http://msgroup.org/videos.aspx
It won't play for me. What am I doing wrong? I get this error message:

"Windows Media Player cannot play the file. The Player might not support the file type or might not support the codec that was used to compress the file."

I get a similar message with Real Player.
 

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in general, like Mini nsx said, if you stay above the peg grinding angle you probably will not lose traction on a normal road.

At an instantaneous point in time, as I recall my physics.....
---an object in motion tends to stay in motion...so the bike is trying to go in a straight line off the road in a tangent to the curve
---the bike is leaned into the curve so the bike is constantly 'falling' in toward the center of the curve... just enough to counter the straight line outward tendency.
---the gyroscopic action of the wheels, helps keep the bike relatively stable and free from wobbling
---the friction between the road and the tire supports the weight and holds the bike 'up'.

Every successive instant, you are scrubbing the tire slightly across the asphalt in the slightly new direction of turn..creating a slightly different tangent... and THIS is where friction and contact is so important. If that friction is lost...for whatever reason....then the 'go in a straight line" effect will take the bike off on a tangent to the curve while slightly leaned over... and the 'fall inward' lean you had going will put the bike down. That is a low side crash.

Tire surface condition and temperature and inflation and braking...anything that affects its contact area and friction coefficient are important. The scraping of a peg is warning you that something solid on the frame is very close to the road....and IF a frame element hits the road solid, and lifts the bike and tires upward a bit, the lost friction may be enough to cause the low side crash above.

I suspect you can turn a low side crash into a high side crash in that situation pretty easily if you jam on brakes and the front tire grabs the road again suddenly.... ( like if you start a low side crash because you rode up on the center slippery paint stripes...and then come off that onto dry road again ....which almost got me this weekend...luckily I didnt panic and hit the brakes....just rode thru it.... )
 

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This site has some interesting links you might like, Jeep.

http://www.motorcyclephysics.com/

I especially liked the Wikipedia link, what applies to bicycles applies to motorcycles too. There's way more information there than anyone in their right mind needs to know. LOL!
 

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It won't play for me. What am I doing wrong?
I couldn't get the vids to play either. Tried both my browsers, Firefox and IE and they don't play either. We must be missing some codec or helper app but it doesn't say what. :confused:
 

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Discussion Starter #11
Hey, I fired a whole bunch of synapses that had cobwebs on them.... I need more feedback !! :)

made sense? helped? was off base?

???
Sorry dude! You input was not just input... it was usefull input. Thanks for the synaptic calestenics. I understand better now how it works. Turns out I was not to far off base to begin with. I just sort of know my boundaries better now. Also, the lean into the turn to set the bike up straighter thing is cool. I knew racers leaned into turns, but I didn't know why. And by the way, you are a lot easier to follow that my old Polish Physics prof Dr. Lapicki. It was bad enough to be trying to learn a new technical field, but when you miss every 3rd word because of the profs accent, now that's hard.
 

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Preen...preen... GRIN.

Thank you! and you are very welcome... :)

Annie "the dude"... :rolleyes:



Sorry dude! You input was not just input... it was usefull input. Thanks for the synaptic calestenics. I understand better now how it works. Turns out I was not to far off base to begin with. I just sort of know my boundaries better now. Also, the lean into the turn to set the bike up straighter thing is cool. I knew racers leaned into turns, but I didn't know why. And by the way, you are a lot easier to follow that my old Polish Physics prof Dr. Lapicki. It was bad enough to be trying to learn a new technical field, but when you miss every 3rd word because of the profs accent, now that's hard.
 

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Discussion Starter #13
Preen...preen... GRIN.

Thank you! and you are very welcome... :)

Annie "the dude"... :rolleyes:
Dude.. your a girl! My bad. I sort of glaze over the user names sometimes. Espcially since most of them are acronyms. I guess I sort of assume everyone on here is a guy since 90% of riders are men. Sorry to get you all gender conflicted. Until otherwise advised, I will now imagine Tallannie as a mid-twenties slim, athletic, biker babe.
 

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you just made my day....LOL...




Dude.. your a girl! My bad. I sort of glaze over the user names sometimes. Espcially since most of them are acronyms. I guess I sort of assume everyone on here is a guy since 90% of riders are men. Sorry to get you all gender conflicted. Until otherwise advised, I will now imagine Tallannie as a mid-twenties slim, athletic, biker babe.
 

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in general, like Mini nsx said, if you stay above the peg grinding angle you probably will not lose traction on a normal road.

At an instantaneous point in time, as I recall my physics.....
---an object in motion tends to stay in motion...so the bike is trying to go in a straight line off the road in a tangent to the curve
---the bike is leaned into the curve so the bike is constantly 'falling' in toward the center of the curve... just enough to counter the straight line outward tendency.
---the gyroscopic action of the wheels, helps keep the bike relatively stable and free from wobbling
---the friction between the road and the tire supports the weight and holds the bike 'up'.

Every successive instant, you are scrubbing the tire slightly across the asphalt in the slightly new direction of turn..creating a slightly different tangent... and THIS is where friction and contact is so important. If that friction is lost...for whatever reason....then the 'go in a straight line" effect will take the bike off on a tangent to the curve while slightly leaned over... and the 'fall inward' lean you had going will put the bike down. That is a low side crash.

Tire surface condition and temperature and inflation and braking...anything that affects its contact area and friction coefficient are important. The scraping of a peg is warning you that something solid on the frame is very close to the road....and IF a frame element hits the road solid, and lifts the bike and tires upward a bit, the lost friction may be enough to cause the low side crash above.

I suspect you can turn a low side crash into a high side crash in that situation pretty easily if you jam on brakes and the front tire grabs the road again suddenly.... ( like if you start a low side crash because you rode up on the center slippery paint stripes...and then come off that onto dry road again ....which almost got me this weekend...luckily I didnt panic and hit the brakes....just rode thru it.... )
Fwiw, high sides are caused by the rear tire losing/regaining traction.

For the op, as others have said, all things being equal (tire condition, road condition, etc.), you'll hit hardware before losing traction.
 
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