Difference between revisions of "Head Angle Change With Suspension Travel"

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According to very accurate calculations that I have done, the head angle will change on a hard tail mountain bike approximately 0.0521° per mm of travel if it has a 1058mm initial wheelbase. The bottom bracket height will change approximately -0.3868mm with each mm of suspension travel.
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Wheelbase is the overriding factor for how the geometry changes. Different wheelbase bikes will change at different rates. Other factors contibute, obviously, but their effect is very, very minor.
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Different wheelbase bikes will change at different rates.
 
 
==Formulas==
 
==Formulas==
 
Here are the equations:
 
Here are the equations:

Revision as of 16:04, 16 December 2007

Wheelbase is the overriding factor for how the geometry changes. Different wheelbase bikes will change at different rates. Other factors contibute, obviously, but their effect is very, very minor.

Formulas

Here are the equations:

  • A12 = Initial Head Angle
  • B12 = Fork Offset
  • C12 = Sagged fork length
  • D12 = Initial Wheelbase
  • E12 = Initail BB Height
  • F12 = Chainstay Length
  • G12 = Wheel Diameter
  • H12 = Fork Compression or extention from sagged

These formulas are not designed to work with 2 different wheel sizes and do not account for tire deformation or chassis/fork flex.

Otherwise, they are perfect.

Head Angle Change

Head-angle-change.gif


Head-Angle-Change-with-Trav.gif

Bottom Bracket Height Change

Bb-height-change.gif


Bb-Change-with-Trav.gif

Mechanical Trail Change

Mechanical-trail-change.gif


Mt-change-with-travel.gif

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