Originally Posted by
Abu Mahendra
How much bigger is a 451 wheel relative to a 406 wheel?
On my own bikes, a 406 rim with a 42mm-wide tire (Schwalbe Marathon Supreme) measures 50cm in diameter, while a 451 rim with a 28mm-wide tire (Schwalbe Durano) measures 52cm in a diameter.
I found the following formula to be close enough to the roll-out diameter, which is the one that is used for gear-inches (but not necessarily for frame clearance)
Wheel diameter = ERD + 2* tyre width
e.g. 406 + 84 = 490mm
451 + 56 = 507mm
My Moulton front measured=480mm; calculated
406 + 37*2 = 480 spot on
Moulton rear measured 495mm; calculated
1.75"*25.4*2 + 406 = 495mm spot on