thirdcrank wrote:It's hard to understand how that damage might have happened.
I have had damaged like that happen to a couple of tyres over the years. One was recent and the tyre was a Schwalbe Big Apple. The other was many years ago and the tyre was a brand new Marathon Plus. In both cases I believe it was due to me running over large flints (I was cycling in the (Chalky) Chilterns on both occasions). It was the back tyre in both instances. The flint was flung out with quite some force as it escaped from my back wheel as I ran over it. Of course I don't deliberately try to ride over flints but sometimes you can avoid them with you front wheel but the back wheel follows a different track, especially if you are going slow because you are picking your way around potholes or climbing.
I was particularly gutted about the Marathon Plus because it was supposed to be puncture proof and it had only been on the bike for a week.
Here is an old post about it. I had forgotten that I tried to boot the Marathon Plus and the boot left me down. With hindsight I should have scrapped it immediately.