text: my finace' gets erections when we drive over speed bumps.? if we are driving and we hit alot of speed bumps in a row it's instant erection. there's no hiding it. what could be the cause of such an odd reaction? who cares what the cause is...what a blessing i say.   the perfect date is to get him in a jeep and do some off road trail driving for about a hour!  why after that your boyfriend should sleep for a week solid.