In the top picture the spacer is removed but there is still a lip on the shaft. On the parts list and on videos it appears the shaft is all one diameter. Once reinstalled the lip is up against the outer sheave. At idle the belt seems to sit half on the larger diameter lip. The bike is definitely faster but I was worried the belt would wear unevenly. Basically you have the outer sheave, larger diameter of the lip, smaller diameter of the shaft, then the inner sheave. The belt at idle sits on that thin lip and not the shaft itself.