http://www.crazyguyonabike.com/forum..._id=140170&v=3
The above is hearsay, but I do recall in my surfing some admission from Schwalbe itself that they had discontinued the XR. The XR is not mentioned in Schwalbe's 2010 product lineup.
Another bit of hearsay....
http://www.crazyguyonabike.com/forum...age=1&nested=0
Anyway, I can't find anything else while quickly retracing some of my earlier surfing.
Well, if the XR is discontinued what would you use for the GDR in 47or50-622? Front and rear.