Modern LEGO wheel hubs are known to suffer from a lot of slack. Other drawbacks are that you can only use them with CVT joints - not with the stronger and more angleable U-joints - and the section inbetween the pin holes of the hub is wider than 1 stud.   While playing with one of them I noticed that part of the slack is because the DBG pins don't sit very tight in the wheel's pin holes. It helps a little if you have an axle running through the wheel which extends into the DBG-part of the hub. Now I know @nicjasno sells modified wheel hubs based on small turn tables, which have much less slack than the original wheel hubs. But than you still can only use them with the weak CVT joints. And you have a modified part. So I looked into using a turntable as wheel hub for the 15038 wheel (with 6 pinholes) without modifying it and it gives quite a good result. Better than the LEGO wheel hub: The turn table is attached to the wheel with 2 3L pins. The assembly inside the wheel makes sure the turn table's pinholes are attached to a pin and not to an axle (which would give slack) and sits tight against the inside of the wheel to give stability. Finally an extra belt wheel is attached to the wheel to give even more stability to the 2 3L pins that connect the assembly to the wheel.