You might see bike tire load limits in catalogs. The Schwalbe catalog has load limits.

http://www.everybicycletire.com/shop...-115-load.aspx

I assume that load mean the amount of weight on a particular tire, which would be the rider, bike and gear, but only the part of the weight which is born by the tire. The rear tire would be carrying more weight than the front.

But, like others I question that the load limit is what is causing Swan's flat issue.