I would think 8-9lbs per wheel in rotating weight would be noticeable, and especially on the CF angle. I always wondered why city buses don't have Alum wheels (6?), since they start and stop nearly every block, for their entire life cycle and alum wheels them saves 40+? lbs per wheel, but fire trucks have them and they maybe move twice a day?
Maybe the steel wheel is more durable in that situation, going around all day on bad streets on a bus full of people. If it fails, it would probably bend but not break.
