Are the Michelin Hydroedge tires being discontued or just certain sizes being eliminated? I am trying to get one Hydroedge P215/55-16 UPC 91T to replace one that has a non-repairable edge of tread nail hole. I purchased 4 of these tires about a year ago and have 19,000 miles on the set. Now need to replace the one tire and the two local tire dealers say they can no longer get this size. Any thought on where to get one Hydroedge tire this size? The tire is a UPC 91T and a UTQG 800 AB. If I cannot get the exact size and UPC 91T replacement do I need to replace 2 together to keep the same tires on the same axle? Thanks Slick