Modern Vespa

I have a question. The manual says the GTS have a "hydraulic servo operated brake". I can hear the engine sound change when i press the rear brake so there seems to be a connection there. How does this system work and why is it used. The front brake on a bike needs to do more work than the rear so why is the rear servo operated?

The front and rear brakes are operated by the same mechanism. "Hydraulic servo" is just a fancy name for the system that virtually all disc brake systems use.

The engine noise changes because when you engage the rear brake, the calipers grab the rear disc and alter the vibration characteristics of the engine, essentially attaching the engine to the frame (albeit temporarily) at an additional point. It doesn't have anything to do with load on the engine or anything like that.

Aaahhh...now I see. Thanks for the explanation jess.