Board Thread:Game Discussion/@comment-28401107-20170614095839/@comment-27613933-20170614102033

It's partly due to more racers competing. As the total goes up overall, you end up with more people in the top ranks (as they're done by a percentage of the total competitors).

As people ahead get bumped up the ranks then the time to the next rank gets closer towards your target time.

I remember one week where I was constantly moving from group D to C and back again as I was right on the cut off between the two. As people improved I got dropped back, as new people were slower I got bumped up.