Vibration on ringtone is enabled by default on iPhones, but you can easily turn off vibration on ring or when the iPhone is silent. To enable / disable vibration on iPhone devices running latest iOS version, do as follows:
1. Open the Settings application
2. Tap the Sounds option to open the settings
3. Now there are to options to manage the vibration on iPhone: Vibrate on Ring and Vibrate on Silent.