I assume you're talking about a penny farthing, us not having a section for road bikes on here an'all. Best bet is to take the brakes off the bike altogether so you're more areo & lighter & it saves the namby pamby notion of going anywhere near them. All you need do is pop open your waistcoat and use it as a parachute brake, if you need more stopping, unbutton the bottom of your plus fours and hold your cap open like a butterfly net until you reach a reasonable dismounting speed, say 25-30 mph, then simply hop off and catch the mounting peg as it goes by.