Why can't I store my sled with the wheels on?

Why can't I store my sled with the wheels on?

We are working on fine tuning the foam filled wheels to be able to do this, but we have had flat spot issues when people have left them on for extended periods of time. If this happens leave them in a hot or sunny place for a few days and they will come back. To prevent issues with flat spots just slip a short board under the skis to lift them slightly off the ground. This takes less than 10 seconds to do.