Page 23 of the BMST Rule Book:
2. O. (IV) LEATHERS
Suits made of synthetic material are not permissible. The use of stretchable Kevlar and perforated materials in non- critical areas are permissible. Leather suits shall be one- piece design or joined by a full circumference zipper at the waist. Leathers cannot be too big or loose. Critical area (knees, elbows, forearms, shoulders) armor or 2-layers of leather is highly recommended. Due to invisible flames, riders’ of motorcycles burning fuels of Methanol content are recommended to wear Nomex underclothing or something of similar nature.
We do not have a rule on leather humps. It's the machine that gets classified for records, not what you are wearing.
The BMST has different rules than the SCTA.
Stay fabulous,
Linnea