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June 17th, 2014, 09:17 AM
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#1 |
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wat
Name: wat
Location: tustin/long beach
Join Date: Sep 2009 Motorcycle(s): wat Posts: Too much.
Blog Entries: 5
MOTM - Oct '12, Feb '14
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flexy frame?
so in high speed banked corners it feels like the frame is slowly twisting back and forth on my oem ex250j frame. i'm wondering if there are any technique or setup things i can change to lessen the frame flex without having to actually change the frame? would a shorter wheel base lessen the torque going into the frame? maybe the bike is sitting too high? or i am too far forward? maybe a stiffer front engine cradle mount thinggy?
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June 17th, 2014, 09:30 AM
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Daily Ninjette rider
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
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Quote:
When you straightened your frame, you could see how much force was needed for twisting it back, and that was without the bracing effect of the installed engine. The forks may be the weakest link in your case. Here is a good link about what happens in the forks. http://www.tonyfoale.com/Articles/Steer/STEER.htm This is the general rule of thumb for tubes in structures. - Excellent for resisting twisting or traction forces. - Not so good for resisting compression forces, especially if they are slender. - Bad for resisting bending forces. Certain degree of yield or deformation always precedes any fracture, more for low carbon steel and vice verse. 
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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 |
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June 17th, 2014, 09:32 AM
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#3 |
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The Corner Whisperer
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
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You didn't know the frame is part of the suspension on 250s?
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Goal: Shake A Million Hands | Look through the corners | Track Day Prep | Closest track? | The Mid-Ohio School |
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June 17th, 2014, 09:46 AM
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#4 |
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The Corner Whisperer
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
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Seriously though... I think you're making (minor/unconscious) steering corrections mid-corner that starts the whole mess.
The frames do flex yes... but I have never felt it "twist". I would describe it more as a "humping" or "rocking back and forth" action and more toward the front near the narrow part of the frame head. I get the flex bad at Mid-Ohio but not near as much at Putnam (where I am faster and more confident).
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Goal: Shake A Million Hands | Look through the corners | Track Day Prep | Closest track? | The Mid-Ohio School |
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