After all three cars failed scrutineering at the 1997 event, they had to be modified in order to be allowed to race. This subsequently led to overheating problems for the gearbox, and ultimately led to their failure during the race. That is why for 1998, the R390 was modified, most notably in the extension of its rear bodywork to create increased "luggage space" in order to satisfy the ACO, a new rear wing for racing models (the road legal version had no wing), and a rear diffuser for improved downforce were added.