What type of material is typically LESS effective for managing friction in a brake bar rack?

Rubber is typically less effective for managing friction in a brake bar rack due to its inherent properties. While rubber can provide some friction, it often lacks the durability and heat resistance found in other materials like steel or aluminum. Brake bar racks require materials that can withstand high temperatures generated during braking, and rubber can degrade or lose its effectiveness under such conditions. Steel and aluminum are preferred because they handle extreme conditions better, providing consistent and reliable friction without prematurely wearing out. Plastic, while not as effective as metal, can still provide a certain level of friction management but is generally less favored than rubber when compared to the steel or aluminum alternatives. Therefore, rubber does not meet the critical performance needs of managing friction in this context.