When Ram originally published the cargo capacity for its van, it simply did a direct conversion from the European rating of 15 cubic meters to 530 cubic feet. However, that didn't take into account the standard way internal measurements are calculated for the US. While the trucks have been on sale since October, the automaker just noticed the problem, and it's working on a revised figure. According to Automotive News, the new carrying ability for the ProMaster is likely between 450 and 475 cubic feet.
The difference stems from two standards for measuring capacity. In Europe, the entire internal area is determined and then obstacles like seats are subtracted from it. That means areas where freight could never go, like on top of seat backs, gets included in the figure. In the US, only the area where goods could actually fit is included, which leads to lower specs with no actual change in space.
Companies that buy vans often prioritize volume when choosing a new vehicle. With the change in measurement, the ProMaster's capacity drops from second to third place in the segment. According to AN comparing the largest version of each van, the Mercedes-Benz Sprinter leads the category with 547 cubic feet of storage, followed by the Ford Transit at 487 cubic feet. The revised ProMaster should still have a significant advantage over the Nissan NV that offers 323 cubic feet of capacity.
We've contacted Ram for more details on how this mistake happened, and we'll update this story when we receive a reply.