Ok, we have a rubber surface, and another surface (say tar) that are rubbing together. The amount of heat that is produced would be dependant on the friction coefficient between the two surfaces, the inital tempuratures of the surfaces and how much they are slipping against each other. The amount of heat would build up over time, dependant on how much heat the surfaces can dissipate, and hence the smoke volume produced.
When the surfaces stop slipping against each other, they stop producing additional heat, but it takes time for the builtup heat in the surfaces to dissipate, and hence the smoke volume decreases similarly.
When the surfaces stop slipping against each other, they stop producing additional heat, but it takes time for the builtup heat in the surfaces to dissipate, and hence the smoke volume decreases similarly.