In the "Riding and Draft Animals" section of Creatures & Monsters, various Horses, Donkeys, and Mules have, among their stats, a Carrying Capacity listed. The Note at the bottom of the chart states that that this is the amount that the animal can normally carry before incurring penalties.
What penalties are those, exactly? I cannot find the answer in Creatures & Monsters nor in the Rolemaster rulebook.
For example, a Pony has a Carrying Capacity of 180 lbs. I assume that from 0-180lbs, the Pony moves its' full Base Movement rate of 70'. What happens after that weight? Is there some weight-multiple that it goes down to half-rate? One-third? What is the maximum weight that it can carry and still move?
I was thinking of using the Character's Encumbrance chart in the main rules (or making one based off of it just for steeds), but that doesn't seem to be right.