Really strange!! I was given a black gear to fit when I had my gears done, by a race car builders who knwo all about Mustangs, I can only assume it was a 20T one, but the speedo is still 10mph fast, I have 235/45/17 on my car and the Hanlon Motorsport website says thats what I should have. If I had 245/45/17 then I would need the 19T one, think I might just buy one anyway to try and solve this mystery!!
