Tire turning on Rim

[Schulmann]

What might cause the tire to turn on a Rim ?
I just put new set of Kumo tires on my Viper and one of the rear tires is slightly but steadily turning.

 

[95Viper]

Pressure but darn...you'd have to be realy low and hit it hard

 

[Schulmann]

The pressure is the same on both Tires and only one tire is turning. It is not so bad but in long term the tire will suffer. Maybe I put to much soap on one of the tires.