I wanted to lower my handlebars (a 0 degree rise with a 100mm stem) on my Specialized Allez and when I went to the Specialized website, I couldn't find the stem I wanted. Then I realized the stems they sold were adjustable including the exsisting stem I have now ! The only problem is how do I adjust it and how do the shims work? I prefer to do it myself than have a LBS do it because I have a bunch of tools left behind from building up my Surly Cross-Check.
This is the stem if it helps:
And right now, it says +16 and -8. How much can I expect to lower my bars?
From what I gather, it looks like I adjust the stem rise by turning the shim around and flipping the stem.