[vstolpner]

Well you could always just place a starting marker, and start breaking at that market and then measure (the most obvious way).

Otherwise you can measure using an OBD adapter. This would be either via stopping time or stopping distance, depending on the phone app you're using. Torque, for example, gives me stopping time.

For example mine shows 3.3 seconds. Assuming a straight line deceleration, that works out to be about 44m (144 feet). If adding bigger breaks then reduces it to 3.1 seconds(again, as example) then the stopping distance is reduced to 41.3m or 135 feet, or about 9 feet improvement.