where it says there best distance is on their profile page
i find regularly this isnt there best distance

how do you go about finding the best distance for a horse ...do you start as a 2yo at 5f and then keep stepping them up and down in distnace

as 2yo i run horses whose profile is 5f-7f over 5f races to begin with. then progress the 6f and 7f up to 6 towards the end of the season.

1m and 1m1 horses will normally get 6f early and then progress to 7f and 1m towards the end.

1m2 and 1m3 horses are better started over 7f early or 1m later on as 2yo.

the best indicator is the stamina bar. if you play regularly enough you will get to know which distance is correct by gaging this.