There is no definitive answer to this question as it depends on a number of factors, such as the specific model of pop up trailer, the axle size and capacity, and the weight distribution of the load. However, as a general guideline, most pop up trailers can safely support an axle load of up to 2,000 pounds. Therefore, if you are unsure about the specific capacity of your trailer's axle, it is always best to err on the side of caution and keep the weight of your load within this limit.