Step 9: It’s a good rule of thumb to replace tubes whenever you change a tire, but if the original is still usable then it’s ok to re-install it. Locate the valve stem hole from the side you just spooned on. Insert a tire spoon as if you are going to pull the tire back off, fold it over and pin the spoon handle under the sprocket. This will create space for you to work in when trying to install the valve stem. Flip the wheel over so that the brake rotor is up. Place a foot in the middle of the rotor and squat down to provide pressure. Lift up on the tire sidewall with one hand and use the other hand to tuck the tube inside. Once the valve stem is through, use the lock nut to keep the stem from pulling back through. Proceed around the rim making sure that the tube isn’t twisted or folded on itself. It helps to have a little air in the tube, but not enough to stretch the rubber.