Hardtails are mountain bikes with only front suspension. Their simple design allows long, care-free days in the saddle, and they are lighter and more versatile than their full-suspension counterparts. Choose between 27.5 and 29" wheels depending on your body size and riding style. Smaller riders who prefer improved agility might prefer the slightly smaller wheels, which are also quicker to spin up to speed. If you're taller and prefer greater stability, you may find prefer a 29er - the larger wheels enable you to get over trail obstacles more easily.