How to Easily Put a Back Tire on Your Mountain Bike
To put a back tire on a mountain bike, first, flip the bike over and loosen the skewer on the hub. Slide out the old tire and tube, then put the new tube inside the new tire and partially inflate it. Put the tire back onto the rim, and starting at the opposite side of the valve, work the tire bead back onto the rim with your thumbs. Make sure the tube is fully seated inside the tire before inflating it. Finally, tighten the skewer and check that the tire rotates freely without rubbing on the frame or brakes.