I have never had to use any shims on the wheels....with the correct 17mm hex type wheels it is a direct fit and then you just tighten down the nut and ur good.
They do have an upgraded nut that is serrated to bite into the plastic wheel and when I switched to those, I have never had a wheel come off while running.
If you are trying to widen the track width, they do have different hexes for that and a pair of hexes come with a pair of upgraded wheel nuts as a bonus. Or they sell the nuts in a pack of 4.
The part numbers are listed in the manual and then search on serpentamerica.com
If you are talking about slop on the outer hinge pin, there are shims that came in the kit for that. It's a tuning option to move the hubs on the pin.
Speed Passion....Speed Power....Serpent America/Desoto Racing.