How are you guys measuring the diameter? The lip always ruined any attempts for me. The lip can't be included in the measurement.
The best I could come up with was wrapping a string around it in one of the grooves and doing a little math. =/
Yet, the belt doesn't ride on the lip, and the lips can be different lengths depending on the pulley. Maybe not a big difference, but the lip diameter isn't great for any calculations.
A caliper would probably be the most accurate way, a lot better than a piece of string.
For those looking for a handy caliper. Harbor Freight sells a 6" digital caliper #47257 and it's accurate. Regular price is supposed to be 30.00 but it's usually on sale for 10.00 or 12.00.
9.99 at my local harbor freight, i am about to go down and buy it....Usually I do not like having a digital item like this but it could be more useful since it is so cheap.
And they also have a 1000 gram digital scale I will buy also so I can weigh the UR pulleys I have.