Swap DA 7900 172.5 chainset for 170.0

Don't worry about formatting, just type in the text and we'll take care of making sense of it. We will auto-convert links, and if you put asterisks around words we will make them bold.

Tips:

• Create headers by underlining text with ==== or ----
• To *italicise* text put one asterisk each side of the word
• To **bold** text put two asterisks each side of the word
• Embed images by entering:
   
  That's the hard one: exclamation, square brackets and then the URL to the image in brackets.
• * Create lists by starting lines with asterisks
• 1. Create numbered lists by starting lines with a number and a dot
• > Quote text by starting lines with >
• Mention another user by @username
• For syntax highlighting, surround the code block with three backticks:
  
  ```
  Your code goes here
  ```
  Just like Github, a blank line must precede a code block.
• If you upload more than 5 files we will display all attachments as thumbnails.

For a full reference visit the Markdown syntax.