Six consecutive months of strong Class 8 order volume ended abruptly in May, according to data tracked by research firm Stifel Capital Markets. Class 8 orders in May topped 16,800 units and while that’s up 18% compared to the same month in 2016, it’s down 30% sequentially from April and below expectations, noted Michael Baudendistel, vice president of Stifel’s transportation and logistics research group, in a statement.