Time to change the rear tire
Just as everyone has their own expectations for tire longevity and performance, there are many choices of tires in the marketplace. Too bad that the Spyder has only one choice across the broad spectrum of Can Ams from the lighter F3s to the heavier often loaded RT's. If you have 13,000 miles on your rear Kenda Road-Kil you did good, but it is time to get it replaced as I haven't seen a pic of much tread on them at that mileage. I just changed the rear on the wifes 16F3T at 13,880 and one side was bald (wish I took a pic) and the otherside was down to the wear bars.
I do think that Kenda is beefing up their tires as I remember 10,000 used to be good. I also think that the fronts run long enough as long as you don't have any belt issues and have been getting 26-30,000 out of the last two sets. Oh well just my two cents.. to each their own.