Pretty sure no proportioning. Would need smaller rear wheel cyls for less rear bias. Ebooger used to sell (7/8" iirc) ones for reasonable money. Some semi met front shoes might be a faster/cheaper partial solution. EDIT might tighten the fronts to where when you hand spin the front wheel(s) (forward) you hear a slight "tick" at one point in the revolution and tighten the rears to that point for an equal reference then loosen the rears a # of clicks. Check your pedal reserve (height) when done