You got a digital caliper?
Did you know that all of the v belts I've tested are not consistent to their stated dimensions along its top width? The top width varies along the belts length sometimes up to .8mm. That's no good. Vibration and shitty wear will result.
Breaking in a wobbly ass belt will just give you a more wobbly belt.
So I made a v belt dressing jig.
Got some sticky coarse 40 grit sandpaper and set The jig to the thinnest width part of the belt, then manually pull the belt thru until the belt is even. Then it should keep that proper width while it wears in.
I checked the belt and it has a .7mm diff across the top. WTF?
I use 2 belts so you can imaging the vibrations I had with them at high speed. I measure the thinnest width on the belt first, then mark with a paint pen. Then check high spots. I pull the belt thru a few times and measure. Keep doing this until you're within .1-.2mm
It was fucking easy as shit and my bike has never been smoother.
If you see the belt going up and down in your pulleys when pushing it around, you got a wobbly ass belt bitch!
I should sell this jig.