Front Brake Upgrade in Mechanics Posted Tuesday at 10:20 PM · Report reply Before you reach for the zippo, the standard Sierra brakes will stop a car with 5 passengers etc. comfortably. Your car is nowhere near that weight, could you just refit a servo if you have room, If not you could just fit a smaller master cylinder, I believe the KA ones are 21mm and Sierra 22? so little difference. I think people have fitted 19mm in the past. I had thought about removing the servo on mine but driving with it disconnected was terrifying!