If you find the valve is the leaker you can replace it without removing the wheel...or the tire.
Use a beefy C clamp on both sides of the tire next to the edge of the rim by the leaky valve: squeeze the tire beads until one side pops off the shoulder of the rim, push the loose tire wall to the side so you can reach in and remove the valve remnants (you already snipped off the top of the valve flush with the rim), insert a new valve lubed with soapy water, and pop it in, gently pulling with a vice grip fastened on a metal thread cap (to protect the valve threads). Then you move the tire wall as you have your air pump going so it touches the shoulder and seals enough to start inflating and pop the tire bead back on the shoulder.
Total time to do the job: 30 minutes, max. Warning: Do not push more of the tire bead off the shoulder then the small amount needed to reach in to the valve. Why? Because you might have a problem reinflating the tire due to so much of the bead not touching the shoulder and sealing for inflation.
