Yesterday to avoid a large forest fire I had an unplanned trip over Buffalo Pass in Colorado which is about 5 miles of light to intermediate Rock plus 30 miles of gravel/dirt on my 09 R1200gs. I have mostly worn (7k miles) tkc 70 tires that I aired down to 34 R 30 F since I also had about 140 miles of high speed pavement. I was quite surprised that they seemed to grip better than the new TKC 80's on my Tiger 800 over the same pass and was quite happy with the performance on the GS. I was worried that I would be picking up the bike, but went for it anyway as I did not want to breathe thick smoke for 100 miles. I have been considering swapping the tires on the bikes to evaluate them on the GS but it is expensive and a hassle. I realize they are different bikes and the TKC 80's will probably out perform the 70's in deep sand and mud but would be interested in opinions on those that have both. I am thinking of just putting another set of 70's on the gs as I use my other bikes for extremely difficult terrain. It seems that the pattern on the 70's might actually grip dry rock and gravel better than 80's and offer higher mileage and better road performance. If the GS gives me everything the Tiger offers and the extra 55lbs of real world weight is carried lower on the BMW than the Tiger it may be redundant and should be removed from the fleet.