Speeding is dangerous, so you always want to travel at or below the posted limit. While the law varies by state, the general consensus is 15–25 mph over the speed limit (or more) is reckless driving.
Most often, reckless driving isn’t clearly defined as a certain number of miles per hour over the speed limit. Instead, it’s wanton or willful disregard toward the safety or property of other motorists. As such, many states leave it up to the law enforcement officer’s discretion.
So, you could be traveling less than 25 mph over, and the officer can choose whether to give you a reckless driving charge or a speeding ticket—or both.