The TKC 80 up front on a GS/GSA can't be beat (19' or 21"). They're just expensive and don't last as long. I agreed to try the C17 only because I was going to be doing seven long days of unfamiliar terrain in Baja and wanted to be sure I had as aggressive a dirt tire as I could get. The E09 Dakar will suffice off road too and have better on road manners than the C17 and still last you longer than the TKC 80. Not sure yet about tread life on the C17 as I only have 1400 miles on it right now. It looks pretty darn good still. I used the 21" TT which is bi-directional (doesn't matter how you mount it).