If it was the chain would there not be a bit of the sidewall missing? From the photos looks like there's no damage.
Not necessarily, chains do have an amount of lateral travel (it's one of the ways to see how worn they are compared to a new one) It only needs to contact briefly to remove a chunk of tyre If it moved far enough to damage the sidewall I think it would jump off one or both sprockets, then the tyre would be the least of your problems The damage looks like it's been removed by something fairly blunt at pace (due to the "ripples" along the cut section) If I'm wrong please let me know, then we can all learn something
I've been riding and messing about with bikes for about 36yrs now, and I've probly made a fair few of the mistakes that can be made (thankfully very few these days ) ... we live and learn don't we
Thinking about it, there is no way the chain could do it normally, as it ain't that slack.... You would need something extreme under loading to do it.... Like air on a hump back bridge maybe???? Maybe mystery solved!! Lol
On the chain route, yeh I went out with the tape measure. 13mm "mm for Ken" from the inside of the chain to the tyre wall. Am I right in thinking you run 55's Jimbo? Even so as said. The chain IMO would have to be that slack to get enough lateral movement it would have come off well before then. And perhaps evidence all around the side wall would be visible? I reckon you've been a victim of a drain cover or something similar mate. Probably on a road that's recently been re dressed. It's not uncommon for the planer to hit the ironwork leaving a sharp edge?
Could be wrong but isn't the very edge of the tyre where it meets the sidewall closest to the chain? Looking at the photos there is no damage here and there is still the little rubber bit where it's released from the mould. To do that damage would the chain not have to wrap itself round the tyre thus avoiding the closest edge,and at that point you'd have more to worry about than a bit of missing rubber I'd go with a piece of glass pressed into the warm tar by a car.
A number of things could have caused that, but all Road based damage I'd say. Glass, Metal Shard Sharp edged Pot Hole Metal Grid Plate in road with failing Tarmac at the edge Fecked Cats Eye's have sharp edges! Sharp Masonary droppings Kids with Knives, who aint 'all that'!
