The tag "animdist" is the circumference (in metres) of the wheel being animated. In nearly all cases just putting in that number will work.
However, a few animations are different lengths. They are normally 30 frames, but sometimes different lengths are used, particularly when it is animating a set of wheels that are different sizes as in the Swiss Krokodil locos, or tram car bogeys where each pair of wheels is a different size. Then the animdist value can also depend on how many revolutions a wheel does 30 frames of the animation.
If you can't get the wheels to rotate at the correct speed, download AssetX from the link in my signature below. Use it to open a text view of the animation. It will tell you the animation length in frames.. It should be 30 frames. It it is not then you may have to experiment with values way outside the normal values for animdist.
As a short guide, if the wheels are running slow, put in a smaller value of animdist.