The ADD saw that the HSU (Hydropneumatic Suspension Unit) provides better mobility and crew comfort. At that time, the HSU caused problems with some equipment and it was yet to be fully verified for durability, igniting controversy internationally. Therefore, it was inevitable to introduce and localize a British Air-Log (now Horstman) HSU that is used for the AS-90. However, when researchers applied the Air-Log HSU on the MTR and prototypes, they soon found that the HSU couldn't support heavier vehicles, thus failing the durability test. Since May 1997, engineers from the ADD and Dongmyeong Heavy Industries have spent a year on five redesigns and 11 durability tests. After the development of the new HSU, the design was exported back to Britain.
