> How do I determine the correct chain length?
The formula I learned many years ago is easier to do than it
is to describe:
Measure the distance in inches from the centre of the
spindle [at the dustcap] to the centre of the rear axle.
Multiply that distance by two, and round the product up to
the next whole inch. Call this number A.
Add the number of teeth on the largest chainwheel to the
number of teeth on the largest sprocket. If that sum is
odd, add one to get an even number. Divide the resulting
sum by two. If that quotient is odd, add one to get an even
number. Again divide the result by two, and call the final
quotient B.
Add the numbers A and B and one to get the chain
length you need.
For example, one of my bikes has a centre-to-centre distance
from the spindle to the rear axle of 17-3/4 inches. Multiply
by two and get 35.5, so A is 36 [the next whole number].
The largest chainwheel has 53 teeth, and the largest
sprocket has 28, so their sum is 81. This is an odd number,
so add one to get 82. Divide 82 by two to get 41. This is
another odd number, so add one to get 42. Divide 42 by two
to get 21, so B is 21.
Adding A and B and one, I get 36 + 21 + 1 = 58 inches of
chain.
