This is my version of "why do they put metric fasteners on the forks"? I have always went with the fact that Harley has been using Showa front forks on their heavier bikes (at least) since Shep was a pup. Showa is a Japanese company, thus metric. I believe that the Japs fill their forks with fish oil instead of petroleum based oil. It makes you want to hurl when you take it out of the forks. Very dark too. I believe it is called "Capella oil".