SinoSoldier
Colonel
Type 99's road wheels appear similar, if not identical, to those on the t-72. But gaps between each pair of road wheels appears to be substantially larger. So it seems to me that type 99 hull is significantly longer than that of t-72. This would significantly increase type99's weight for the same level of side protection as on the t-72.
I have not seen photos of type 99's power pack. But I understand it is based on German MTU design. German tank power packs seems to all be designed with the crankshafts running front and back, while Russian MBT power packs seem to generally to have the crank shaft run side to side. This suggests type 99 needs a longer hull compared to t-72 in order to accommodate the German designed power pack.
I would be careful when claiming that the T99 has the same level of side protection as the T-72, especially when the T99 has significantly different turret design and armor composition (hence armor density and weight); it would be like erroneously comparing an Abrams to a King Tiger tank purely based on weight and dimension.