 With front and rear suspensions the only parts unsuspended are the wheels and small parts of the front forks and rear chain-stays.Even then, as mountain bikes have large low-pressure tires which allow much more travel than small high-pressure road tires, the wheels are sprung to some extent as well.In general, bikes are so light compared to their riders that travel is a much bigger motivator than unsprung mass in determining where to put the suspension and how much to use.