I'm having a hard time finding time finding a new rear tire anywhere in the country. I'm not picky - any road legal knobby will do. A dealer I semi-trust says he can get me a Metzler Karoo 3's BUT they are from 2016. It'll be a month and a half before Metzler, Continental, Pirelli, IRC get new tires in here. Is 3 years old an issue? Though typically I like both MT21's & 606's I've had issues in the past with both those tires having whole blocks of tread break off when they were new. Now I'm wondering if that was just because they were new "OLD" tires and I didn't know it?