On the rear, if you notice bands forming around the center:
you'll go from running on rubber to running on steel belts in around 200 miles:
It lasted me about 6800 miles. The front is still in GREAT condition at that same mileage.
Spud,
Ended up contributing money to Adventure Motosports in Twin Falls yesterday. I started a trip to Salmon, ID from St. George, UT on July 15. I had 3497 miles on the BT 023 GT's. Judging from the rear tire wear bars, etc. I thought I could make the round trip. I had a new No Mar Changer and new PR2's waiting at home. Problem was I took a little side trip to Dillon, MT, and another day to Stanley, ID, which added to the "round trip".
When I stopped for fuel in Shoshone, ID yesterday (about 20 miles north of Twin Falls) my rear tire looked like your picture above. Problem was I had 500 miles to go, to get home! And that 500 miles was on US 93 through such metropolises as Wells, NV; Ely, NV; and Panaca, NV. (No moto tires in those places!!) Also, I appreciate your posting of these pics, as I had read your post and knew I didn't have many miles left.
So, upon arrival in Twin Falls I used my "smart" phone to find the aforementioned dealer. They were great, sold me a Metzeler Z8, and I was on my way 2 hours later, but it was a very expensive lesson. I'd purchased the No Mar because of the high labor charges associated with tire changes/balancing. I should have changed the tire before I left. The dealer did a good job, got me outa there quick, but charged a premium. I guess I don't blame them, either. Expensive lesson learned, if there's any question, put new tire(s) on!!
How many miles did I get out of the rear BT 023 GT?? 4937 miles. The front tire still looks good with a little flat spot and some cupping. It will go for awhile longer. I'll see how far this Metzeler goes, and then the PR 2's.
Oh, and on this set I did no 2 up riding, and 2 longer trips of 1k + miles with loaded side cases.
Bob