We are looking at one side of the wheel only. Calculate each side
seperately.
For a 36 spoke wheel we use 18 spokes on one side.
All units are typically mm but can be whatever you like.
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o = offset of the flange from the center of the hub
Radiuses:
h = radius of the hole circle of the hub
r = radius of the Effective Rim (ERD / 2)
s = radius of the spoke hole
L = SQRT ( oo + hh + rr - 2hr cos(a) ) - s [ general ]
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a = 360 ( crossings / spokes ) [ degrees ]
a = 2PI ( crossings / spokes ) [ radians ]
For a 36 spoke cross 3 wheel:
a = 360 ( 3 / 18 ) = 60 degrees
Luckily cos(60) = 1/2, so
for a 36 spoke cross 3 the equation is:
L = SQRT ( oo + hh + rr - hr ) - s [ 36 spoke cross 3 ]
Example:
DMR Revolver SS hub:
h = 58 / 2 = 29
o = 39 = 39
s = 2.6 / 2 = 1.3
Specialized Saturae HX22 rim:
r = 555 / 2 = 277.5
L = 265.8
Mavic XM719 Disc Rim
r = 539 / 2 = 289.5
L =
L = SQRT ( oo + hh + rr - .765(hr) ) - s [ 32 spoke cross 3 ]