Head Angle Change With Suspension Travel

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.

Different wheelbase bikes will change at different rates.

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.

Otherwise, they are perfect.

Head Angle Change

Bottom Bracket Height Change

Mechanical Trail Change