That is the way Triumph, in their wisdom, set it up.
At one point I had the speedometer accurate, and odometer leading low, but I didn't like it. I was getting frustrated at all the slow drivers - all the time. It is now set back to OEM and I don't get annoyed at slow drivers - as often. With the DS tyre there is about a 2% discount due to the larger diameter tyre. When the speedometer is reading 80 I am really doing about 76, which is fine for me.
