If you sent Soma an email, they would probably tell you how much of a load you could safely carry on the ES. My guess is that the load capacity would be more of a function of what RACK you use rather than the frame. If you're using the Soma for commuting, I doubt if the loads you carry are any concern -- unless you are one of those people who carry a bunch of gear while commuting. I bike commute regularly on 5 different bikes, including two touring bikes, a sport tourer, a cyclocrosser and a racing bike. My commuting loads probably average 5-10 lbs and I am not the slightest bit concerned about carrying that amount of weight on any of my bikes.