If one wheel spins more slowly than the others, the cause may be the wheel, bearing or hardware around it. A quick spin test can help narrow the problem, but it does not measure how the setup will perform under a rider.
Check for contact and tightness
Lift the board and spin each wheel by hand. Look for a wheel rubbing on the truck or another part. Check that the axle nut is not so tight that it stops the wheel turning freely. The nut must still be secure; do not leave it dangerously loose to make the wheel spin longer.
Check the bearing position
If the wheel is clear and the nut is set correctly, check whether both bearings sit squarely in the wheel and whether any spacer or washer is correctly positioned. Compare the affected wheel with a wheel that spins normally. Avoid forcing parts into place.
Swap only if you can do it safely
A careful swap between wheels can show whether the problem follows a bearing or stays with the wheel or hardware. Reassemble the parts in the correct order and secure the axle nut before riding. If a bearing feels rough, sticks or is damaged, replace it.
See the installation guide and contact DSCO if you cannot identify the issue.